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bobsmyuncle
01-31-2014, 10:41 PM
I'm revisiting the pioneering footwork of others as seen here;

http://www.lxforums.com/board/showthread.php/274935-My-Journey-for-bigger-brakes-on-an-SRT8-on-a-budget-(DIY-SRT8-Big-brake-kit)?highlight=amg+calipers

and here;

http://www.lxforums.com/board/showthread.php/330480-AMG-Big-brake-upgrade

and would like the input of others as it applies strictly to our needs on the road course.

The short version of the above is that the 8 piston front calipers from a 2003 - 2006 E55 AMG, (years to be confirmed) CL55 AMG, and, (years to be confirmed)SL55 AMG are a direct bolt on to the SRT knuckle but requiring either machining to use a SRT rotor, or going to a larger 16" rotor. NOTE - there are certainly other makes/models using these calipers.

At this point I haven't worked out the details of the rears. I'll update as I sort through that info, which will likely with input from the pioneers be sorted out in the above links.

My intent with this thread is to alert the road course guys of the existence of this potential mod, and to iron out it's real life feasibility.

So points of conversation;

will they indeed fit the 18" wheels many of us are using?
is the performance worth it? Lets consider that we are using a quality racing tire.
pad selection, is the OEM 'good enough'?
Pad selection, is the price manageable for our crowd?
are rotor costs (considering one piece only) manageable?
other makes/models using these rotors?
any other thoughts

So I acknowledge that there are more cohesive 'out of the box' solutions in a 6 piston format and in an 8 if the Brembo kit suits your finances (yikes). So we don't necessarily need to beat down that door.

But if we could source an affordable caliper and rotor combo, is this something we actually want, and can live with for the long haul out on the course?

I'd love to see some constructive discussion, especially involving the more experienced guys here, but also those of us preparing ourselves and vehicles for entry into the hobby.

In the meantime, I'll be knocking on some doors and looking into affordable solutions.

UpInSmoke
01-31-2014, 10:56 PM
Subscribed

Jontoad
01-31-2014, 11:43 PM
also will be watching this...

Meech
01-31-2014, 11:45 PM
Ditto What Jon Said ^^^

todd0218
02-01-2014, 12:18 AM
The most affordable I have seen are the 6 pot ctsv/camaro brembos. I think 300-400/ea.

I was thinking of trying one to see if it fits a srt spindle without modding. Then contacting adams rotors to take a ctsv camaro rotor and drill it for a 5x115 bolt pattern.

That's as far as I got...lol

modesto83
02-01-2014, 08:34 AM
Subscribed


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DA H.N.I.C.
02-01-2014, 10:58 AM
Subscribing for updates

Todd TCE
02-01-2014, 01:17 PM
You guys might be a bit disappointed in how these "big" brakes perform. "But Todd...these have 8 pistons, not 4 or 6~!" Cool. But lets look deeper.

By my sources (please verify) they have two 28mm and two 32mm pistons per pad. In brake speak the calipers have 4.4sq" of piston area.

By way of comparison your stock Brembos have two 44mm pistons per pad. In brake speak the calipers have 4.7sq" of piston area.


That's 5% less clamping force. To get that back (brake torque) you'll need either MUCH larger rotors, far more aggressive pads or a move to the smaller bore master from the RT to bump up the line pressure. Or you could just push with both feet.


Pulled up some other info also. My Wilwood set ups for the SRT8 (you can't buy them from any other Wilwood dealer) have 5.3sq" of piston area. Thus about 15% more clamping force vs stock.

Jontoad
02-01-2014, 02:38 PM
I would think the heat sink capability of the 8 piston caliper and the lower fluid temps would help greatly on these heavy cars.

Blown7
02-01-2014, 03:50 PM
You guys might be a bit disappointed in how these "big" brakes perform. "But Todd...these have 8 pistons, not 4 or 6~!" Cool. But lets look deeper.

By my sources (please verify) they have two 28mm and two 32mm pistons per pad. In brake speak the calipers have 3.9sq" of piston area.

By way of comparison your stock Brembos have two 44mm pistons per pad. In brake speak the calipers have 4.7sq" of piston area.


That's a full 15% less clamping force. To get that back (brake torque) you'll need either MUCH larger rotors, far more aggressive pads or a move to the smaller bore master from the RT to bump up the line pressure. Or you could just push with both feet.


Pulled up some other info also. My Wilwood set ups for the SRT8 (you can't buy them from any other Wilwood dealer) have 5.3sq" of piston area. Thus about 15% more clamping force vs stock. Or 35% more than the 8 pots...

OK so lets do some real math...but I don't know how to figure it ...


Maybe the pistons are smaller but the clamping force is spread out over a larger area.. I don't have those numbers but that has to account for something.. maybe cooler?? You can have tons of force on the point of a pin but have the same force on a larger area and it becomes more effective.

bobsmyuncle
02-01-2014, 04:19 PM
You guys might be a bit disappointed in how these "big" brakes perform. "But Todd...these have 8 pistons, not 4 or 6~!" Cool. But lets look deeper.

By my sources (please verify) they have two 28mm and two 32mm pistons per pad. In brake speak the calipers have 3.9sq" of piston area.

By way of comparison your stock Brembos have two 44mm pistons per pad. In brake speak the calipers have 4.7sq" of piston area.


That's a full 15% less clamping force. To get that back (brake torque) you'll need either MUCH larger rotors, far more aggressive pads or a move to the smaller bore master from the RT to bump up the line pressure. Or you could just push with both feet.


Pulled up some other info also. My Wilwood set ups for the SRT8 (you can't buy them from any other Wilwood dealer) have 5.3sq" of piston area. Thus about 15% more clamping force vs stock. Or 35% more than the 8 pots...


I would think the heat sink capability of the 8 piston caliper and the lower fluid temps would help greatly on these heavy cars.

Todd welcome to the discussion glad you made it here!

If indeed your numbers are correct, can we theorize why Brembo would spend the time and money to engineer the 8 pot caliper and why Mercedes would spec it. I'm hoping there is more than aesthetics involved perhaps as Jon suggested heat dissipation?

Todd TCE
02-01-2014, 04:37 PM
Further thoughts:

1. Heat soak of the caliper? That's the purpose of the rotor, not the caliper. If you're overheating the caliper then you need either more rotor mass or cooling.

2. Why does the MB stop so well then if that's all true? From my looking I see a 25mm master is used in the car. (.984) Meaning they run the system at a higher pressure. I didn't compare it but higher pressure on smaller bores vs your lower pressure on larger bores....yes; pretty much the same net result. All of which only mean you push harder or not on the pedal also. How you achieve maximum torque is the goal.

3. But they have larger pads! Yes they do. In part to spread that load over a larger surface area needed by the "padlets" (which ask most track day Corvette owners will tell you suck) so that each pad has it's own piston! Pretty cool huh? Theory is less taper wear. Back to that pad size...so the larger pad must brake more right? Nope, not exactly. Splitting hairs there are some minor changes but pressure pushing on the pad, big or small, is the same pressure and same torque. I don't think that's right Todd. Ok, try this: go stand on the bathroom scale. You weigh 200lbs. Now put on a shoe size 4 sizes bigger and reweigh yourself. Pretty much the same huh? That's pressure, just in a vertical sense.

5. So if all that's true why do they offer these awesome brakes?! Well..let's be honest here...you like them don't you? And you think they've got to be the cat's ass or the car wouldn't come with them. And you'll pay a premium for them. They look great and saying you have 8 pot calipers in your sig puts you in a class by yourself! Pretty sweet. Ok, funnin aside the reality is there are some benefits sure. But nothing more than you can get from other set ups or in many cases not a lot better than what you have now with in some ways.

Todd TCE
02-01-2014, 04:54 PM
Corrected my numbers above also for you.

28/28/32/32 is 4.4sq" not 3.9" making it only about a 5% spread. My mistake, sorry.

I then worked the math with some changes to the mc bores on both cars.



At 60lbs of force AMG with smaller bore calipers and (thought but not verified) 25mm bore mc nets 4642lbs

At 60lbs of force SRT8 with larger bore calipers and 1.063 (1 1/16) bore mc nets 4290lbs

*All other variables the same.


Push 5lbs harder on the pedal and you'll have 4648lbs on the SRT8.

Put that caliper on the SRT8 and you'll have to push with 9 more pounds of effort to achieve that same pressure 4612lbs (remember what I said about both feet?)

The net gains of the 8 pot is that you'll have a firmer pedal. And have to push harder. You won't simply have more brake force. In fact for the same effort you have less than you do now. But most folks like a firmer more responsive pedal also. On the other hand you might take the RT mc and put it with the 8 pots. Smaller bore mc will make up for the lack of caliper pressure and no need to push harder. It's all pretty much a wash in the end.

What to plug and play? HERE (http://www.tceperformanceproducts.com/bias-calculator/)

bobsmyuncle
02-01-2014, 05:00 PM
If I'm not mistaken the W211 E55 was initially spec'd with their hydraulic/electric system (later discontinued), whether the AMG had it or not I'm not certain. Could have something to do with the choices made however.

Note to others, while researching keep in mind there will be significant equipment difference between the standard and AMG models.

I'd be interested in determining what other makes/models used these callipers (ok, a quick aside, does anyone else have a spell check that refuses to spell it caliper? so annoying) and what bore master was used.

Todd one significant challenge I see in using this caliper would be the pad selection. Do you have any insight? I've yet to research that.

Blown7
02-01-2014, 06:14 PM
Further thoughts:

1. Heat soak of the caliper? That's the purpose of the rotor, not the caliper. If you're overheating the caliper then you need either more rotor mass or cooling.

Well there is the argument of the larger caliper releasing the heat from the Brake Fluid quicker and faster and I believe that is were brake fade comes from..




3. But they have larger pads! Yes they do. In part to spread that load over a larger surface area needed by the "padlets" (which ask most track day Corvette owners will tell you suck) so that each pad has it's own piston! Pretty cool huh?

It is my understanding that two (2) pistons are in contact with each pad..




Back to that pad size...so the larger pad must brake more right? Nope, not exactly. Splitting hairs there are some minor changes but pressure pushing on the pad, big or small, is the same pressure and same torque.

Nope...... lets figure Pad Material /Friction working area..... last I checked the more you have of it the better/quicker it is to stop the rotor...
(take my analogy of the pin point to a 4'x8' sheet of material.....)



I don't think that's right Todd. Ok, try this: go stand on the bathroom scale. You weigh 200lbs. Now put on a shoe size 4 sizes bigger and reweigh yourself. Pretty much the same huh? That's pressure, just in a vertical sense.

Wrong analogy....



5. So if all that's true why do they offer these awesome brakes?! Well..let's be honest here...you like them don't you? And you think they've got to be the cat's ass or the car wouldn't come with them. And you'll pay a premium for them. They look great and saying you have 8 pot calipers in your sig puts you in a class by yourself! Pretty sweet. Ok, funnin aside the reality is there are some benefits sure. But nothing more than you can get from other set ups or in many cases not a lot better than what you have now with in some ways.

Well.... I won't pay a premium for a BBK in the $4K range unless it had self replacing brake pads and rotors...

Now when you say "they" you should really say "me" or "I" also offer big brakes... hey it's all about the bottom dollar right?

One thing I see you not discussing IS the benefits... do tell...

Blown7
02-01-2014, 06:36 PM
Ah the term I was looking for is "Swept Area".....

Todd TCE
02-01-2014, 08:09 PM
Ahh, two pistons per pad not one. Believe the Vette is one per or three padlets per side so I ran with that.



As for the pad material/frictional area I'll back up what I said tho. You're discussing what may be called the swept area; the amount of rotor surface covered by the pad in one complete revolution. While the larger pad does in deed cover more total area it does not produce more clamping force. In fact one could argue that there is actually less clamping per square inch of that pad despite it being larger.

A plywood sanding contest is similar but not. Trying to remove a large amount of material would require a larger sheet of paper. However if your goal is to reduce the wood by 1/32" you'll be there for a long time, where as the same hand doing it on a small sheet would take down that smaller area real quick. In any case on a rotor our goal is to generate torque relative to the rotational center. I'll bow out of the argument for area here, if you want to speak brakes; it's a relatively inconsequential matter you'll have to trust me on that one. Larger pads are fit primarily for longer life not to make more torque.

To go one step farther (and address some of those 'benefits') consider the pad size. What? You just said.... I know I did but now...

Take your pad size for example of 2.5" tall by 3.5" wide (view it on it's side, that's how it's done, don't blame me) and compare that to a pad of many racing calipers at a size more like 1.875" tall and 4.5" wide. (think more wrapped around shape like the big 8 pot might hold) Here I did not run the math but for the sake of argument let's say they both have the same total area. You'd think then that they'd produce the same torque. But you'd be wrong. The long slender pad wins on torque. The reason is that the pads (correctly state the pads fit with the proper caliper requiring them) create a higher Er of Effective Radius. The average torque spot or lever point is higher on the disc. Nearly all track pads due this. Street pads can be much larger (ie. fatter) and have less toque even despite having more piston area behind them. A combo of both the location of the pad and that issue of total pressure.

The 8 pot uses some rather narrow pads I suspect. Compare that with the fatter SRT pads. The SRT pads are fat for a number of reasons; street pads need to be more tolerant of run out, quieter, and last longer. This is how some of that is done. Track pads are simply about the most effective way to clamp the rotor- that's at the highest spot.

Other benefits can include lighter weight, improved cooling and response/feel. Alum will be both lighter than iron and shed heat much quicker. A fixed caliper with X number of pistons compared to a floating/slider has wasted energy and movement. Even swapping to the same bore specs one usually picks up a "wow these feel great" response just by getting rid of the free play in the system. Air flow around the larger caliper and that alum body is far more effective than iron. Weight loss is often touted by way of both the caliper and the aluminum rotor hat.




One more thought.

When mfgs build such calipers to wrap around a large disc they try to achieve that high Er effectiveness. That mandates a pad that is quite narrow and in turn a piston that is quite small. Fitting a fat piston with half of the piston area overhanging the pad is not such a good plan. There as a study some years ago on pad size and by the time they had a reduction in clamping force the had lost contact with some of the pad with this relationship.

When the pad gets narrower and the pistons get smaller...the quantity gets larger. It's also in place to control pad tapering.

Blown7
02-01-2014, 09:12 PM
'm not sure where you use the term "torque" in a brake context, torque is a rotational force whereas the brake is actually taking Kinetic Energy and turning it into heat.

I guess the word torque in this discussion kind of throws me a curve ball...

Basically wouldn't you agree that what we want the brakes to do is turn the rotational motion into heat?

And given that the next question would be how to create and dissipate the heat the quickest?

Todd TCE
02-02-2014, 11:47 AM
'm not sure where you use the term "torque" in a brake context, torque is a rotational force whereas the brake is actually taking Kinetic Energy and turning it into heat.

I guess the word torque in this discussion kind of throws me a curve ball...

Basically wouldn't you agree that what we want the brakes to do is turn the rotational motion into heat?

And given that the next question would be how to create and dissipate the heat the quickest?



Never thought of it. I guess because it's just the industry norm.

But I think we view it differently. The brakes are creating torque to slow it as the engine does to make it go. I'm no physics major by any stretch but the way I see it; the heat is a byproduct of the torque. In order to get heat you have to have some sort of motion. In this case it's the clamping and frictional forces on the disc that doe it. The mathematical combo of leverage, Mu, and clamping express in foot pounds like an engine is.

The goal of the rotor is to be able to absorb that heat generated and shed it efficiently. Obviously the larger and wider the disc the more efficient it becomes. You can stop a V6 LX one time probably as well as an SRT8 from 60mph. But I bet you can't do it repeatedly. That duty cycle. The trade off becomes weight and packaging.

Todd TCE
02-02-2014, 12:56 PM
Some further reading for the most engineering minded readers.

As I don't want to appear to be the 'expert' here I'll defer some of the conversation to a much larger (albeit much younger) brake company.


http://stoptech.com/technical-support/technical-white-papers/brake-system-and-upgrade-selection

bobsmyuncle
02-02-2014, 08:34 PM
I want to keep everyone in the conversation so don't anyone be offended by asides and explanations.

Here is a half decent explanation of 'coefficient of friction' http://www.regentsprep.org/Regents/physics/phys01/friction/default.htm



...

As for the pad material/frictional area I'll back up what I said tho. You're discussing what may be called the swept area; the amount of rotor surface covered by the pad in one complete revolution. While the larger pad does in deed cover more total area it does not produce more clamping force. In fact one could argue that there is actually less clamping per square inch of that pad despite it being larger.

...Larger pads are fit primarily for longer life not to make more torque.

One thing you are neglecting is that the size of the contact patch directly affects the heat dissipation which as we know is VERY important in the repetitive braking cycles experienced on the road course.

For those interested in this for street use please keep in mind that we ARE discussing this from a road course perspective. For typical street use, I'd imagine most would agree that clamping force is more important as you will never have issues of heat build up like we are discussing.

On the road course, arguably (and within reason) clamping force is perhaps less important than the resulting shedding of heat.

The coefficient of friction will increase with the increased surface area (keeping the rotors, pads and thus fluid cooler results in better braking). While need that coefficient to be less than 1.0 (less than locking up) we need it as high as possible and can fine tune it with pad choice.






Take your pad size for example of 2.5" tall by 3.5" wide (view it on it's side, that's how it's done, don't blame me) and compare that to a pad of many racing calipers at a size more like 1.875" tall and 4.5" wide. (think more wrapped around shape like the big 8 pot might hold) Here I did not run the math but for the sake of argument let's say they both have the same total area. You'd think then that they'd produce the same torque. But you'd be wrong. The long slender pad wins on torque. The reason is that the pads (correctly state the pads fit with the proper caliper requiring them) create a higher Er of Effective Radius. The average torque spot or lever point is higher on the disc. Nearly all track pads due this. Street pads can be much larger (ie. fatter) and have less toque even despite having more piston area behind them. A combo of both the location of the pad and that issue of total pressure.

The 8 pot uses some rather narrow pads I suspect. Compare that with the fatter SRT pads. The SRT pads are fat for a number of reasons; street pads need to be more tolerant of run out, quieter, and last longer. This is how some of that is done. Track pads are simply about the most effective way to clamp the rotor- that's at the highest spot.

Again in order to benefit the masses, the long narrow pads are placed along the outer circumference of the rotor where they are most effective at resisting the rotation. The conversation is a bit muddled in this respect so far but basically think of it as increased leverage, maybe we can clarify that as we go on.

Adding larger rotors, and thus moving the caliper away from the centre of the wheel increases it's effectiveness in this respect and is one of the main reasons we want to use a larger rotor (another being an increased mass to soak up heat).

So while two pads may have the same surface area, the long skinny one at the circumference of the rotor can do more work than the pad closer to the pivot point (the wheel's centre line).




'm not sure where you use the term "torque" in a brake context, torque is a rotational force whereas the brake is actually taking Kinetic Energy and turning it into heat.

I guess the word torque in this discussion kind of throws me a curve ball...

Basically wouldn't you agree that what we want the brakes to do is turn the rotational motion into heat?

And given that the next question would be how to create and dissipate the heat the quickest?

You are (I believe) absolutely right, but as Todd mentions, it is common to compare the forces at work from the opposite perspective of a lever working to produce torque (or at least rotational movement).

For example it is easier to turn a steering wheel by grasping the outer rim than to turn it from the centre. For the sake of simplicity think of it as 'turning' the rotor in the opposite direction of the wheels rotation.

I guess it is an effective analogy.

Blown7
02-02-2014, 09:01 PM
I also read the Stop Tech article. Although I have heard that Stop Tech tries to bias their articles toward their parts. I prefer SAE whitepapers.

Todd TCE
02-02-2014, 09:12 PM
Larger rotors= greater heat disapation agree totally. Larger pads= no. *Not to the extent the system as a whole will run cooler. You might argue the larger pad has a lower operating temp but pads and rotors aren't intended to be heat sinks.

For a given speed and weight the heat factor is constant. A larger and or wider rotor will prevail. A larger pad won't do much of anything.

The Cf of the pad never changes by size, only temp. You're wrappping your head around the pressure issue again there. If the Cf is .62 it is .62 regardless of the size of the pad. Assuming the same pressure is being applied.

Northern Rider
02-02-2014, 09:13 PM
Subscribed

Todd TCE
02-02-2014, 09:15 PM
I also read the Stop Tech article. Although I have heard that Stop Tech tries to bias their articles toward their parts. I prefer SAE whitepapers.


We all would of course. But that doesn't change the physics.

Todd TCE
02-02-2014, 09:28 PM
Go back to you blocks of wood for a moment.

The wood's Cf is constant. What's changes is the 'normal force' applied. That's due to the added weight of being applied.

In the brake world running a pad of .62 at 600psi will generate one force- the torque. Double the pressure to 1200psi and you'll double the force- rotor torque. The Cf of the pad has not changed however...only the amount of clamping being applied to it. You can spread that same pressure over 1sq inch, 1sq foot or 1sq yard and the total force remains the same.

Todd TCE
02-02-2014, 09:43 PM
Spot on with regard to the pad at the highest radius. The problem is that to take advantage of the location the narrower pad then needs smaller piston. And more of them. True Er would be defined by the average centerline of the pressure points of the pistons. We simply use half the heught of the pad for simplicity. And a 2" piston on 1" tall pad would create huge pressure problems and pad wear issues! Lol

bobsmyuncle
02-02-2014, 09:50 PM
Larger rotors= greater heat disapation agree totally. Larger pads= no. *Not to the extent the system as a whole will run cooler. You might argue the larger pad has a lower operating temp but pads and rotors aren't intended to be heat sinks.
I agree that pads are not by design heat sinks, but they are by circumstance.



... larger pad won't do much of anything.

I only know what I get from my sources, physics isn't my strong point and I'm certainly no engineer, however I've got a textbook from a well respected automotive educator that clearly states that the size of the pad assists in heat dissipation.


The Cf of the pad never changes by size, only temp. You're wrappping your head around the pressure issue again there. If the Cf is .62 it is .62 regardless of the size of the pad. Assuming the same pressure is being applied. (and same materials used)

I fully understand that I'll go review my post in case I misspoke . Also I amended your statement in red for the sake of keeping things perfectly clear. And with that in mind as the pad and rotor materials heat up, or more correctly if they heat up too much, their physical structure can change (glazing of the pads and hardening of the rotors), which in turn reduces the Cf.

EDIT I was writing this while you posted again regarding the blocks of wood so don't think I'm badgering LOL.

bobsmyuncle
02-02-2014, 10:00 PM
Spot on with regard to the pad at the highest radius. The problem is that to take advantage of the location the narrower pad then needs smaller piston. And more of them. True Er would be defined by the average centerline of the pressure points of the pistons. We simply use half the heught of the pad for simplicity. And a 2" piston on 1" tall pad would create huge pressure problems and pad wear issues! Lol

And good point made on the need for the increased number of smaller pistons, I honestly never made the association despite it being so obvious.

bobsmyuncle
02-02-2014, 10:05 PM
The book I referenced i Automotive Brake by Jack Erjavec. I'm not at home to refer to it however. Also I realize this is but a single source but he is highly respected in his field.

sik300srt8
02-03-2014, 12:13 AM
I'm looking at this kit from AP RACING

05-13


300C SRT-8
Front
APR51200
AP Radi-CAL
6P
B,R
410x36mm
2pc
XD/S or S













05-13


300C SRT-8
Rear
APR51600
AP Radi-CAL
4P
B,R
380x28mm
2pc
XD/S or S

bobsmyuncle
02-03-2014, 01:32 AM
I'm having problems confirming Mercedes (AMG) part numbers but the Brembo Part Numbers are 20.7919.01 and .02 cast into the caliper themselves.

This SEEMS to be (I'd bet a good chunk of change) to be the same caliper as offered in Brembo's 8 piston GTBBK Part Number(s);

In the format 1GX.9026AY

X = 1 for cross drilled rotors, 2 for slotted rotors

Y = 1 black, 2 red, 3 silver painted calipers

Blown7
02-03-2014, 09:04 AM
It seems that "Clamping Force" is a term thrown around alot...

Well it seems that no matter how many pistons there are, and given the working pressures that the ability to clamp the rotor "tight" (stop rotation immediately) can be achieved by most braking systems used in the last 30 years on OEM stuff... at least once in a cycle.

Lets move on to why Brembo feels that 8 pistons is very good..with full stop repeatability . with the compounds of the pad that they create, and the brake fluid used.... along with the type and design of a full floating rotor that they feel they can command a price of $4K for...

We can argue all day about clamping force and for me at this point it's moot...old GM cast iron floating calipers will "clamp" and stop any rotor once....

Blown7
02-03-2014, 09:08 AM
I'm having problems confirming Mercedes (AMG) part numbers but the Brembo Part Numbers are 20.7919.01 and .02 cast into the caliper themselves.

This SEEMS to be (I'd bet a good chunk of change) to be the same caliper as offered in Brembo's 8 piston GTBBK Part Number(s);

In the format 1GX.9026AY

X = 1 for cross drilled rotors, 2 for slotted rotors

Y = 1 black, 2 red, 3 silver painted calipers\

If you look at the design of the older AMG calipers (I have a set coming off eblay) the new BBK design has a cast or machined bridge from one side to the other. The AMG has a bolted bridge that makes a 3 piece caliper thats probably why no P/N's cross over.

From what I can find online the mounting bolt measurements are all 180 MM

MattRobertson
02-03-2014, 04:32 PM
This many years into the platform, I think we've answered the questions on whether or not the SRT system can handle track duty. We've also answered the cost questions. What this AMG option offers is an answer to the incredible Chuck Norris Approved Badass Looking Brakes question. Ignoring for a moment the mathematics associated with the physics, lets look at the mathematics associated with the wallet. I'll use a 2007 SRT vs. a 1998 C43 AMG and go to Rock Auto to see what parts cost.

Rotors (Front)
SRT: $45 (Raybestos) each
AMG: $229 (Centric) for the budget option. or $529 (Wagner) for premium. Thats EACH.

Pad prices look to be comparable for both uber track pads or street pads.

Since you will wear rotors out if you are tracking, I'd say you are insane if you want to set yourself up for that kind of replacement cost.

Nothing will out do the Chuck Norris effect of the AMG units, though. Except the calipers on the new Jeep SRT's. The 2014 SRT Jeep's big bad rotors run between $70 and $100 each on RockAuto. You guys should be looking at those calipers... which also are 8-padlet Brembos. And RockAuto wants less than $50 for a new set of OE-material pads. Which means they are track-capable (having driven a Jeep SRT on Laguna Seca last year flat out I'll vouch for them being able to do it just fine).

Blown7
02-03-2014, 04:40 PM
Nothing will out do the Chuck Norris effect of the AMG units, though. Except the calipers on the new Jeep SRT's. The 2014 SRT Jeep's big bad rotors run between $70 and $100 each on RockAuto. You guys should be looking at those calipers... which also are 8-padlet Brembos. And RockAuto wants less than $50 for a new set of OE-material pads. Which means they are track-capable (having driven a Jeep SRT on Laguna Seca last year flat out I'll vouch for them being able to do it just fine).

Well the new 2012+ WK2 Jeep SRT calipers are a definite no go on the WK1's .The WK2 SRT8 calipers are a cheap bastard copy that are specifically made to fit that particular knuckle. And the WK2 calipers are 6 piston not 8.
I've tried a dozen ways to Sunday to make the WK2 Jeep calipers fit a WK1 but given the universal fit of the AMG calipers it looks promising.

And yes my plan is to use the WK2 rotors with the AMG calipers.






.

MattRobertson
02-03-2014, 05:04 PM
OK well $70 to $100 per rotor beats the hell out of $225-$500.

Whats the weight difference set-for-set? I know the SRT rotors clock in at 26 pounds each. God only knows what the weight diff is for the calipers. What are you adding per axle before vs. after?

I can't shake the feeling here that the compelling arguments are all going to fall around looks. For an Lx... For the Jeeps I got nothin' :-)

bobsmyuncle
02-03-2014, 05:57 PM
I'll know more on Friday or Saturday but I believe an associate has successfully and easily (which is the more important factor) machined an AMG caliper for use with the SRT rotor.

I haven't seen this, with my own eyes but since he is in the industry I'm hoping he knows what he's talking about. I wasn't going to mention this until I laid eyes on it myself but I don't want this thread to lose momentum over the next 5 days because of lost hope lol.

There is also the option of a custom rotor which really is no big deal.

Affordability is imperative for track use at least for most of us. So the project IMO depends used calipers and affordable rotors and pads and pad choice.

Right now finding WK2 calipers affordably would be next to impossible I'd imagine. Blown7 I'm getting that term straight from you what do the WK stand for?

MattRobertson
02-03-2014, 06:17 PM
Would that mean they have done something to let the rotor seat itself more deeply so the pads aren't hanging off anymore?

The adam's rotors guy linked in the other thread should be able to do rotors ... but I bet nobody is going to be able to do it truly economically like @ the level of the current Jeep SRT or LX SRT rotors. Still, if you have a choice it ought to be for more rotor to go with the big caliper.

'WK' is to the Jeeps what 'LX' is to our cars. Its the platform designation.

bobsmyuncle
02-03-2014, 06:32 PM
Would that mean they have done something to let the rotor seat itself more deeply so the pads aren't hanging off anymore?

The adam's rotors guy linked in the other thread should be able to do rotors ... but I bet nobody is going to be able to do it truly economically like @ the level of the current Jeep SRT or LX SRT rotors. Still, if you have a choice it ought to be for more rotor to go with the big caliper.

'WK' is to the Jeeps what 'LX' is to our cars. Its the platform designation.

Yes exactly. It sounds a little too easy so until I see this with my own eyes I'm considering it a ... misunderstanding (as in he thinks his 6 pots are 8 pots) lol.

And yes I can only assume you are right about the cost.

And yes again, more rotor would be the best choice. Yet if he is right and I can find a good selection of pads we might have a winner. At least in some respects.

Even if performance is only 'as good' I'm pretty confident initial cost will be lower than many 6 pot BBKs on the market.

Rotors would be cheaper

Pads? Not certain but probably more?

Hemissary
02-03-2014, 07:53 PM
WK2 is the Jeep platform designation, based off the 2011 Durango. I agree with Matt when it comes to aesthetics versus real-world use on a race course. If you can source low cost rotors, great. What you also need to confirm is that the proposed W211 caliper assembly utilizes a pad structure that the aftermarket offers a wide range of pad materials for.

One thing I don't know for sure, but by looking at available pics the Mercedes caliper assemblies are not monoblocks. In other words, there is inner / outer assemblies that use bolts to mate the assemblies. With these systems there is significant deflection under (line) pressure which takes away from efficient braking when it's needed the most. You might want to confirm this before purchase. Again, in the looks department, they are eye candy that rivals my BAER monoblock system.

Speaking of which, I'll mention the BAER system, but only in passing as IMO it is prohibitively expensive (I got a smok'in deal). However, from time to time I see complete (4pc - front / rear) BAER 6s 6-piston racing calipers for sale (they get snapped up quickly). If you found a set, talk to Bill at BAER and order the appropriate caliper / knuckle mounts based on platform (RT or SRT knuckle for the LX / LY platforms). Note that physically the front and rear calipers are the same size (huge), but the rears are machined for a smaller array of pistons (they are progressive in size to ensure uniform pad wear) to address brake bias. The silver lining is that both front and rears utilize one of the most common racing pad configurations (DR-11 / ST-60 / D1247), this means an endless choice of pad materials at very reasonable costs (EBC, Ferodo, Hawk, Pagid, StopTECH to name a few).

It can't be understressed the importance of monoblock caliper design, especially at higher line pressures on relatively heavy platforms like ours. Basically the term monoblock means the caliper is not bolted together, but are machined as a single unit from relative stiff alloy forgings (namely 2618 Al/Cu). I believe the Brembo offerings on our rides might all be monoblocks, or maybe it is just the new 2014 SRT Jeeps (WK2) that have monoblock six-piston forgings.

As far as BAER rotors; mine are two piece and on the order of ~$190 (complete and bolted to a 6061-T6 aluminum hat) for the 15" version, they may offer one piece versions - I just don't recall. Because I convinced them to engineer new mounts and hats, I can use even cheaper DV-32 410mm (16"+ and available up to 1.4" thick) rotors from Coleman (one of many rotor suppliers) with the standard means of attachment.

As a result of the 25mm increase in rotor diameter, I went back to the standard level-2 hi-performance pads (less aggressive bite) on the front - which now match the rear pads. The result is lower replacement cost (~$150 / full set). I have lost slightly some of the front end push (and comfort level) associated with really hi-speed corner entry, but that little extra pucker factor means the car is more balanced (to me anyways).

I only had one track weekend to get familiar with the larger front rotors / pads changes, all I can say about these massive front rotors is that they appear to have not suffered at all. Note I was running P-Zeros on 20's (the fronts have the stiffer sidewall for the Bentley), so not quite the rigorous workout as others with dedicated slicks and 18s. At the limits the brake system was hardly working IMO, pedal pressure was fabulous throughout the day but the P-Zeros really took a beating (as expected on these land yachts). Add to this our now-defunked track only put serious strain on the braking system at T1 and 10.

Because the WK2's are monoblocks, and maybe they are different than what was put on the LX/LY platforms (are they?), the fact they might be a new part number (with low movement / volumes) means they might be very(!) reasonably priced from the OEM - at least for a little while...

MattRobertson
02-03-2014, 08:11 PM
The pad costs I saw at Rock Auto and Tire Rack seemed to indicate they were comparable. But here's something a little scary to think about: You are hoping for a robust aftermarket to keep prices down ... on a part that belongs to a limited edition top-of-the-line Mercedes-Benz? Or that matches up with Brembo's most expensive of BBK's?

http://old.foohbar.com/ul/doh_60.gif

Just seems like thats destined to become a premium-priced item. Its already happening with SRT Brembo's. Porterfield still sells the Raybestos pads I have seen others use very successfully on track, but Jumping Jehosophat they are now custom build-to-order items at $400 *per axle*. Screw that noise.

I'm sure there are others who know where to buy a good track pad in today';s market but where are you going for advice 3 years from now for those AMG pads? I own a Benz myself and man oh man those Benz forums are *nothing* like what we have here when it comes to discussion of modding or tracking cars.

MattRobertson
02-03-2014, 08:20 PM
Simon - SRT Brembo calipers are 3-piece deals. Two outer shells bolted around a center piece. Brembo does calipers as an oem for a bunch of different vehicles using the same two outer shell pieces and just varies the width of the center piece. Simplifies tooling, parts etc. It also explains in part why there are so many track pad choices available that fit and why most of them can't handle an SRT's weight.

Speaking personally, monoblock calipers seem to be chiefly championed by the guys who forked out the big bucket of coins necessary to buy them :P. No question its better technology. Is it functionally better in a meaningful way? Look at all the cars that haven't crashed who don't have them.

Hemissary
02-03-2014, 08:31 PM
Well it seems then the FCA engineers have changed to monoblock design - at least on the 2014 WK2 model year; http://www.drivesrt.com/news/2013/06/grand-cherokee-srt8-hallmarks-brembo-braking-system.html

Todd TCE
02-03-2014, 09:21 PM
I'd call into question to some degree the true advantage to a monoblock caliper today. (like we haven't covered enough relatively meaningless stuff thus far for the Joe Consumer..)

In the days of light weight billet or light castings the desire to produce a caliper from one piece vs bolted assemblies seemed ideal. However with the first such parts problem with grain structure proved the plan to be less than effective. Not until parts were produced from forgings or forged billets did they come into their own. The problem is that not far behind that came the conventional 2pc caliper of the same material and much of the hype got lost to the production costs and competition.

Today most all manufactures offer 2pc. And do quite well on them. Baer only recently converted some of their parts to 1pc and it's still not all the listed parts that I'm aware off. Total bridge area, material, bolts, basic design etc all contribute to the overall structure of the caliper. And as was rightly pointed out: the smaller the calipers piston area the greater the need for clamping pressures thus the greater the need for a yet stiffer caliper. It's an endless cycle.

Search the web some and you'll find yet more, and greater detailed info on the two designs.

Wilwood only recently took the W series caliper to the next level of design by incorporating a bridge in the design.

53206

One of the problems with many 1pc calipers is the you lose the "top load" functionality of design. You have to remove the caliper to swap pads. Not always the most ideal of situations. The Aero6 however remains a 2pc.

For the most part one can rightly state the monoblock caliper is superior by design. But the flip side is cost and maintenance for many.

The net result of all that is just that Joe Consumer is quite unlikely to know whether his caliper is 1pc or 2pc based simply on driving it. If the system is designed correctly the need for 1000psi and potential deflection issues is quite low. I mention this as I point out again that this 8 pot caliper has less piston area than stock. You will need either a larger rotor (leverage), a higher Cf pad (track- noise and dust) or higher pressure (clamping) to achieve the same or greater goals.


*****Coming full circle here some four pages in...my main goal was not to argue, educate or disrupt other than to point out just because it has 8 pistons: that doesn't make it better.

FWIW..Rotora has the lead right now in signature bragging rights with their twelve pots. Stop playing in the sand box and own the beach~!

53207

Todd TCE
02-03-2014, 09:38 PM
And for those of you who just can't get enough Brake Porn..

I recall some nice Raybestos Race Calipers a few years ago at PIR.

53208

Or maybe if money were really no object..the PFC folks build some nice stuff also.

53209

joelvan
02-04-2014, 11:30 AM
From the results that I get with the OEM Brembos while Racing. I would have to be given a new rotor and caliper setup for me to even consider trying anything else. I have never had any type of failures on track with the OEMs. You guys can post all the engineering coefficients you want. If you put on a set of Carbotech pads and add Coolers to the OEM setup. they will lock up and slide 305mm slicks at the end of a 1hr race . After it is all said and done the friction limit of the contact patch of the tire is all the braking you can achieve. once you go over that you are sliding the tires. The only advantage you can get by spending extra money will be in weight savings, or looks if that is what you are into.

Hemissary
02-04-2014, 12:51 PM
^^Good advice; btw Joel, is your ABS still enabled or 100% disabled (removed)? If so what have you done regarding bias?

If it was me and I was motivated to head to the road course as often as I could, I would look closer at the monoblock offerings on the 2014 SRT GCs. I would find out whether pad configuration is the same as previous version used on LX/LY to confirm there is a wide selection of pad material, then I would find a VIN off of a 2014 and go online (significantly better pricing) to see what the calipers are selling for.

Again - as with most brand new parts offerings for new-model platforms, they can be dirt cheap until they volumes start to rise...

They use a 15" rotor it's not a stretch to use existing (and relatively inexpensive) LX platform SRT rotors.

From there it is a simple case of doing the proper measuring to have brackets machined to fit your platform (or maybe they fit the existing LX/LY SRT knuckles).

Speaking of online MOPAR resources; here's the ones I use regularly. A couple of them are also extremely effective at finding PNs of any model year, especially platforms that are not covered by the parts books (.pdf files) we are all (hopefully) well-aware of and have downloaded from members who are kindly hosting FTP sites;

http://www.factorychryslerparts.com/aboutus.aspx
http://www.factorymoparparts.com/
http://www.moparpartsoverstock.com/p/DODGE__REGULAR-CAB-PICK-UP/PAN--PLUG-Engine-Oil--Oil-Drain/6674181/05080631AB.html
http://www.factorychryslerparts.com/aboutus.aspx
http://dodge-wholesale.com/catalog/

bobsmyuncle
02-04-2014, 02:10 PM
This many years into the platform, I think we've answered the questions on whether or not the SRT system can handle track duty. We've also answered the cost questions.

So what factors lead you to using the Wilwood W6A, pad choice?

bobsmyuncle
02-04-2014, 02:34 PM
^^Good advice Joel...

And I'll ask you the same question, if you agree that this is good advice why the move to the Baer system?

FWIW I now have confirmation that the 8 Pot works with slight machining on the factory rotor and fits an 18" wheel. I'll be confirming whether MY 18 fits possibly as early as Friday.

Hemissary
02-04-2014, 03:12 PM
And I'll ask you the same question, if you agree that this is good advice why the move to the Baer system?

FWIW I now have confirmation that the 8 Pot works with slight machining on the factory rotor and fits an 18" wheel. I'll be confirming whether MY 18 fits possibly as early as Friday.

At the time the decision was made, and given I have an RT with wheels / spacers / studs that are geared around the RT knuckles, to fit the OEM Brembo system would have meant either designing caliper mounts and / or replacing the F / R knuckles. I was also looking ahead as to whether it was feasible to increase rotor diameter for better braking efficiency (been down this path before on other vehicles).

Then a post appeared for the BAER system off of a SEMA Charger RT. The projected cost of parts to adapt the Brembo system, weighed against what I eventually paid for the BAER system made the choice a no-brainer (overall design, pad type / availability / cost, fit and finish, actual performance and functionality)...especially from a looks (30%) and performance (70%) POV.

The icing on the cake was that the type of mounting system it employs made it a rather simple process to incorporate larger rotors and if I desired (although overkill), carbon ceramic rotors / pads that were available in a D1247 configuration.

If the BAER system had not materialized, I would have very likely moved forward along the same lines as Matt.

If I had done nothing, and knowing what I know now (courtesy of rickdogg) about the Mercedes caliper systems, and the fact we no longer have a road course around here for the forseeable future, I would be pursuing those AMG 8-piston units along with the appropriate sized rear versions and rotor availability / diameter - based on brake bias requirements and actual pad selection / availability.
Along with this, based on Matt's experiences with the 1-piece SRT rotors and (now) knowing their actual service life on our (heavy) platforms I would endeavor to locate (again) larger diameter rotors and have hats machined to match. The fly in the ointment of course would be (again) measuring and machining mounts to allow for larger rotors.

But that would be all part of the fun IMO...

joelvan
02-04-2014, 03:13 PM
Simon,
My ABS is still at it's factory setting. It does all the bias control. I do think it is the weakest link for racing. Only because it seems to go into a full ice mode occasionally. It modulates the pulses to the point to where it is letting off more to keep the tires rolling than it cares about stopping the car.

I call it a ice mode. Because, the only time I have felt it on the street I was jamming on the brakes while on a large patch black ice for giggles.

The ABS is great, until you reach that level.

When this does happen. I quickly realize my balls have out ran good sense. The pedal feel is rock hard while hardly any braking effort being applied to the tires.

Usually means **** is going badly really fast.

This has only caused me to go off track one time . It does happen occasionally when braking hard in a negative G area such as cresting a hill. It makes me butt pucker every time it happens.


I have driven race cars with real heavy pedal effort and ones with very little pedal effort. The cars with a medium pedal effort give the best feedback and are the easiest to modulate under hard braking. Thus keeping lockup or ABS intervention at a minimum. that is what you want on the race track . The SRT team did an excellent job developing our braking system.

My competitors mouths drop open when I tell them after a race that I out braked them for a in a much heavier car consistently. That I run a OEM braking system .

Hemissary
02-04-2014, 03:30 PM
Interesting; I forgot a couple of times to turn off my RT-based ABS as well as the DSS module disable.

First time, did not notice during warm-up lap, it resulted in my first unplanned(!) track exit...backwards. The first corner was off the 1/4 mile track run-off so entry speed was, well...high. It was my overcorrecting in response to the in-your-face ABS inputs that had me thinking about the upcoming damage as I went along for the ride :^(

Next time was not so bad, but it drove home the point I needed to ensure everything was as off as it was going to get...even then it's still not 100% off.

Sidenote; one of the neatest things I did was to get Johan to program very aggressive / early fuel cut-off to capitalize on engine braking off that long straight into T1...

joelvan
02-04-2014, 03:44 PM
Im not trying to jack the thread. I just figured you all would get a kick out of me screwing up. Old video with stock engine and automatic still in the car . The end where the car went into full ABS ice mode. It was all driver error. I had the red mist in my eyes and went in way too deep.




.
http://vimeo.com/33154029

Jontoad
02-04-2014, 04:06 PM
I have had your ice mode happen a few times. Any time there is not enough weight on the front wheels it happens. I think it might actually happen to me on the autocross course more. The uneven parking lots trigger it. I have had it on public streets too. There is one stop light that can do it every time, especially in the rain. There is a gap across the pavement kinda like a reverse speedbump. I let off the brakes right when I go over it to prevent it. Lol.

Todd TCE
02-04-2014, 05:12 PM
Shooting off on another tangent for a moment new readers may not know that Matt and Hemmisary had more limited choices "back when".

In the early days there were no Wilwood (factory) kits. Only the TCE caliper kit with BSL6 calipers and the full 14" kit also with those caliper. Wilwood had zero interest in the Magnum/300C and were happy to see me sell a few kits. Then one day they realized the Charger was coming out and a number of other dealers couldn't get the same kits I'd been making for a few years...surprise; they were suddenly on board to make complete kits. At the same time I was working on the new W6A caliper for the larger Brembo disc. Matt was a huge help here in that he went step by step through the options: BSL6 on 13.6" disc then BSL6 on Brembo 14...and finally onto the W6A set up on the Brembo. From day one I was not wanting to do that mid level kit but it was the only game in town for a short time.

I'd say about this same time Baer came out with a kit for the car also. Wilwood to this day only offers the kits for the RT and not the SRT. (you can go through me for that on a front kit) Not sure if Baer offered(s) both or not. For many its cheaper to swap backwards to the RT knuckles (ie. cheap) and then simply run the RT brake kit.

Then some years into all that along came the Jeep stuff and now a yet more advanced Jeep offering still. Today owners have the same "kit" offerings or more. Plus they have the DIYers doing alternative things such as yourselves with the attempts at cross fits from other vehicle. A lot of that just didn't exist back then. Here's nearly 7yrs ago! Could be early Matt?

53216

Blown7
02-04-2014, 06:04 PM
Well having lived with the 2012+ Jeep Calipers for a week or so I can tell you this they weight damn near 20 Lbs, and are pretty big.

If you want to call a regular old aluminum casting a "Monoblock" have at it...

But actually it has a removable tie bolt at the top to help aid pad changes.

The pads are large.

Other than not fitting and they are pretty.

Just won't work for my application. Thats why the big AMG's on my agenda.

http://i25.photobucket.com/albums/c96/Blown7/BrakeBremboupgrade032.jpg (http://s25.photobucket.com/user/Blown7/media/BrakeBremboupgrade032.jpg.html)

http://i25.photobucket.com/albums/c96/Blown7/BrakeBremboupgrade054.jpg (http://s25.photobucket.com/user/Blown7/media/BrakeBremboupgrade054.jpg.html)



http://i25.photobucket.com/albums/c96/Blown7/BrakeBremboupgrade045.jpg (http://s25.photobucket.com/user/Blown7/media/BrakeBremboupgrade045.jpg.html)

Todd TCE
02-04-2014, 06:30 PM
I remember when I began work on the W6A kits for the Jeep SRT8 that everyone kept telling me "your Charger kit will bolt right on"...but for whatever reason I didn't buy it. And when it was all said and done I was right. The calipers are W6A but the brackets are dedicated to the requirement of the Jeep. The difference being the rotor offset I believe. The couple who did the swap seem happy with it.

I think this was the earlier Brembo set up correct?


53218


With the newer 15" rotor I'd do this in the TC6r caliper today.

53219

Northern Rider
02-04-2014, 10:11 PM
Simon,
My ABS is still at it's factory setting. It does all the bias control. I do think it is the weakest link for racing. Only because it seems to go into a full ice mode occasionally. It modulates the pulses to the point to where it is letting off more to keep the tires rolling than it cares about stopping the car.

I call it a ice mode. Because, the only time I have felt it on the street I was jamming on the brakes while on a large patch black ice for giggles.

The ABS is great, until you reach that level.

When this does happen. I quickly realize my balls have out ran good sense. The pedal feel is rock hard while hardly any braking effort being applied to the tires.

Usually means **** is going badly really fast.

This has only caused me to go off track one time . It does happen occasionally when braking hard in a negative G area such as cresting a hill. It makes me butt pucker every time it happens.


I have driven race cars with real heavy pedal effort and ones with very little pedal effort. The cars with a medium pedal effort give the best feedback and are the easiest to modulate under hard braking. Thus keeping lockup or ABS intervention at a minimum. that is what you want on the race track . The SRT team did an excellent job developing our braking system.

My competitors mouths drop open when I tell them after a race that I out braked them for a in a much heavier car consistently. That I run a OEM braking system .

I concur with Joel. Braking under race conditions has a lot of factors: heat dissipation; fade; the 'feel' of modulation in trail braking to bleed off a bit of speed; front to rear transition; feeling the threshold of lock-up; etc..

I also run the SRT OEM system with ABS, with upgraded rotors and pads. There are others things I'll spend my money on before upgrading brakes - such as sorting out the weird dog's dinner of the rear suspension components . . . .

Blown7
02-05-2014, 06:35 AM
I remember when I began work on the W6A kits for the Jeep SRT8 that everyone kept telling me "your Charger kit will bolt right on"...but for whatever reason I didn't buy it. And when it was all said and done I was right. The calipers are W6A but the brackets are dedicated to the requirement of the Jeep. The difference being the rotor offset I believe. The couple who did the swap seem happy with it.

I think this was the earlier Brembo set up correct?


53218



Yes the Red pics i posted are the 2012+ Jeep Brembo front rotors.

Do the Wilwood calipers use a pad that covers the entire braking part of the rotor?

It looks like the Wilwood caliper/pad seems narrow for the rotor???

Also the sheer mass of the Wilwood caliper seems not as massive for strength deflection??

Todd TCE
02-05-2014, 10:07 AM
Yes the Red pics i posted are the 2012+ Jeep Brembo front rotors.

Do the Wilwood calipers use a pad that covers the entire braking part of the rotor?

It looks like the Wilwood caliper/pad seems narrow for the rotor???

Also the sheer mass of the Wilwood caliper seems not as massive for strength deflection??


The pads for the W4A and W6A are roughly 2.25" x 6". They cover an area about 2.25" x 6" regardless of what size or shape rotor they are fit too. If they are installed on a 12" disc with a very small aluminum hat they rub the hat. If they are installed on a 15" rotor with a 9" aluminum hat they still cover 2.25" x 6" and leave a gap to the aluminum hat of about 3/4" to that hat. What do you do about that unswept area? Fit a bigger hat. The pad is not too narrow, the rotor hat is too small for the pad. As we covered earlier; the more 'race oriented' the narrower the pad to take advantage of the higher Er. When we (Matt) ran the BSL6 on the 14.25" SRT8 disc his pad width was but 1.75" not even 2.25". In reality for the same piston area that smaller caliper was in some ways more effective!

Strength and deflection issues are always debatable. If the overall system is designed correctly the pressure in a caliper will no be so high as to have huge deflection issues. And of course there's always a trade off of mass vs strength. Running a heavier caliper is usually a sign of a beefy caliper, sure. But when you move to a full aluminum body part some of the intended gains are also weight loss. Most calipers are designed for maximum strength with minimal deflection and flex within the design criteria of course taking into account weight, overall size, rotor fit, and wheel fit.


Here's why track brake are designed the way they are with a higher Er than street stuff.
This is an older 8 on 7.625 bolt circle hat with the 13" disc showing the cool rotor area around the base of of the pad path. The larger, newer hats are 12 on 8.375 bolt circle to take weight off the disc, create a more stable bolt ring and help in cooling to a bit.

53225

Rose City GC SRT8
02-05-2014, 10:47 AM
Love this discussion! Thanks to all the experts, Matt, Joel, Todd and Hemissary. It's reassuring to know our unimpressive 4-pot BIMBO calipers are pretty dang good.

Todd TCE
02-05-2014, 01:09 PM
Thought I'd put up this image for some comparisons as the pad issue is still being mulled over here as well as on the Cherokee board.


53226

On the left you have a 25lb block of lead on a piece of cardboard measuring 8 x 10" or 80sq inches total.
On the right you have a 25lb block of lead on a piece of cardboard measuring 14 x 14" or 196sq inches total. A nearly 2.5X multiple.


The cardboard has a Cf of say .15 relative to the surface of the concrete.
The lead weighs 25lbs in both cases. This represents the clamping of the caliper in total piston area.
Wishing to push these two items across the floor it takes the same amount of energy of say 30lbs of effort. (that 25lbs weight vs equal/opposite reaction etc times the Cf of the cardboard .15 or roughly 30lbs) Thus the frictional force is about 30lbs.

On the left that force is applied at .375 lbs per square inch. (6oz)
On the right that same force is applied at .153lbs per square inch. (2.5oz)

Things to consider here are:
1. If we push this across the parking lot the smaller cardboard will wear out fast. The larger one will last longer. Part of the problem with the larger sheet however is that all the force is concentrated in one main area. That leads to bending or distortion of the sheet. The outer edge won't meet that square inch goal as well as the part right under the lead. Bending in brakes means the pad plate distorts and leads to premature wear or damage- same force is still applied it's just not doing a good job of spreading it out equally.

2. If we were to consider how best to make the larger one work- we'd put two or more pieces of lead totaling 25lbs on the same larger sheet. That would distribute the same total force or load make it more efficient. In the case of the brake pad we put not one 2.75" piston but two 2" pistons on the pad for a total of roughly 6" piston area. When we look at making the cardboard bigger still we yet again want to more evenly distribute the same load and add more pistons. In order to keep both the total force and the hydraulic relationships in check however we reduce the size of those pistons to keep the total area the same.

Hemissary
02-05-2014, 01:49 PM
Not sure what the issue is; what are you trying to solve?

Note that if indeed additonal pistons are added, and actual surface area increases - so does the clamping force if the same sized (diameter) drive piston is still in-play.

Also note that pad backing plate deflection due to a centered force is immediately counteracted due directly to plate stiffness. The greater the centered application of force, the more force migrates to the peripheries of the plate not under direct load. In other words the wear characteristics (cupping) remain constant irrespective of applied force (pedal pressure).

BTW folks; the brake systems Todd offers is very competitive, my comments about pursuing the latest Brembo offerings was because of the admission FCA is now utilizing Brembo monoblock designs for the 2014 model year.

one other comment about the AMG 8-piston units;

Hemissary
02-05-2014, 03:10 PM
...oops, that comment(!) about the AMG 8-piston units is that the more pistons - the more it wraps around the rotor...the more flexure / splaying of the caliper.

During street driving this would not be an issue, but I suspect (multiple) pad wear on a road course at maximum applied force (pedal pressure - defined by the size of the tire contact patches and before ABS activates) could be problematic...

Todd TCE
02-05-2014, 03:36 PM
Not sure what the issue is; what are you trying to solve?

Note that if indeed additonal pistons are added, and actual surface area increases - so does the clamping force if the same sized (diameter) drive piston is still in-play.




Not solve so much as try to further demonstrate the issue of pad size (cardboard) relative to frictional force. That a larger pad alone is not creating more torque due to its larger surface area. Like you say also about additional pistons being added- it's still relative to the (piston) surface area, not the pad.

*Seeing much of the conversation is being shared on the other forum also and confusion about that and swept area still come up.

And I'm not trying to talk anyone out of their plans (I'd even offer to build parts) so much as I am trying to get those who are perusing it to understand cause and effect.

Todd TCE
02-05-2014, 03:38 PM
...oops, that comment(!) about the AMG 8-piston units is that the more pistons - the more it wraps around the rotor...the more flexure / splaying of the caliper.


You know..that's a good point too. I'm guessing (the FEA pea brain in work here) that the smaller pistons being used would cut that down some?

Quick
02-05-2014, 04:29 PM
Not solve so much as try to further demonstrate the issue of pad size (cardboard) relative to frictional force. That a larger pad alone is not creating more torque due to its larger surface area..

[still trying to get a firm grasp on this part]

Let's say 1 sq. inch of surface with 100 psi will provide the same frictional force of 2 sq. inches of surface with 50 psi.

This would have to be based on the CF being linear to the psi applied to it. Is that the case?

Blown7
02-05-2014, 04:37 PM
Me I'm out of this thread as the original purpose was to discuss the 8 piston mod and the direction of the thread is all useless tech about pad size and width..

I'm off to my machine shop to make it all work but I'll leave you with this..

The WK2 Jeep calipers come up a lot in the conversation as a comparison and poster children of a good braking system........ but...... they are useless to modify in the present form for any vehicle ...other than a WK2 or Durango.

Everybody that have driven the WK2 Jeep says it stops well.. so that being said............

The pad width is 2 1/2 inches wide on a 2 5/8 " inch rotor pad area.........the pistons are 1 1/2 inches in diameter and there are three of them..... if the Brembo engineers are pretty good.. then why did they use a pad width that wide when a pad width narrower is supposedly better as argued in this thread?????

Hemissary
02-05-2014, 04:54 PM
If I'm not mistaken, the focus of this thread is to determine whether the AMG 8-piston caliper is worthy of track duty. It's natural to compare to what folks are using now, and what collectively we have learned. This is occurring.

It is also important to lay the (technical) groundwork so everyone is reading the same into what is being written. This is occurring.

All is still leading to a consensus on the viability of continuously using the AMG 8-piston caliper in a road course environment.

Useless is in the eye of the beholder...

Todd TCE
02-05-2014, 05:36 PM
The pad width is 2 1/2 inches wide on a 2 5/8 " inch rotor pad area.........the pistons are 1 1/2 inches in diameter and there are three of them..... if the Brembo engineers are pretty good.. then why did they use a pad width that wide when a pad width narrower is supposedly better as argued in this thread?????


This is not a difficult question to answer and one you've probably already done.

You have three pistons at 1.5" each. (my guess metric really) for total area of 5.3sq" of piston area. Assuming they are in the center of the caliper body width and the center of the pad they apply X lbs of pressure relative to your leg.

Street pads are by design 'fatter' than race pads. We've covered that and it's not uncommon at all to find "oem" pads to be 2-2.5" tall (wide). The reason is both life as well as tolerance to run out and wear. It has nothing to do with pressure, torque or power. I personally never said the pad was "better" being narrower. I'm simply showing your that the narrower pad WITH the properly designed HIGHER caliper piston placement creates more torque. But wears out a lot quicker!

If that same caliper were fit with 1.5" pistons that favored the very edge of the disc or body of the caliper you could design a pad that is only 2" wide. And you'd have more toque, power, whatever. This is not hard to wrap your head around: the average clamping location is out farther on the rotor. It's the reverse of taking the caliper and putting it on yet a larger disc; you increased the leverage. Try grabbing your torque wrench only half way up the beam; you have to pull harder to get it to click.

Sorry if you are finding such information boring...or useless..or whatever. Believe it or not tho there is some sound science and physics behind some of the parts on your car. And understanding how and why things work as they do is only make one a more educated owner.





Certainly nobody has to agree with me on any or all of this. If you want more insight check with other "name" manufactures including Brembo or AP.


Here are some more brake porn images from AP:
53230

53232


Here are some pad profiles for their popular six pots:
http://www.apracing.com/products/race_car/brake_pads/6_piston_caliper_pad_profiles.aspx

You'll notice that the majority of them are long, slender designs compared to most OE shapes. While we've covered the effective reason for this what hasn't been said about fatter pads for racing is "packaging". Meaning when teams are looking for a long life pad for a 24hr race they need not only thickness but cubic inches also. You can only make a pad so thick before the caliper becomes way wide and has fit issues. They can extend the life of the pad (at a somewhat compromise to effectiveness) with a fatter design. It has to last long. And most race cars don't run 15" discs! They are often fit inside 18 and even 17" or smaller wheels. The pad would become very narrow and require a huge wrap around to fit a 12" disc and last four hours. Too costly and complex a caliper so the make a short fat caliper with fat pads and get more life.

Todd TCE
02-05-2014, 05:41 PM
.

[still trying to get a firm grasp on this part]

Let's say 1 sq. inch of surface with 100 psi will provide the same frictional force of 2 sq. inches of surface with 50 psi.

This would have to be based on the CF being linear to the psi applied to it. Is that the case?


Nope. 1sq" with 100psi will provide the same force as 2sq" of surface with 100psi behind it.
The total force is the same, the force pound per square inch is different yes, but not the sum total.

Pads don't work by selecting only part of it to function (but for that pad bending issue on s single pot!) but rather apply the total force of your hydraulics over the entire surface- thus spreading the load just like the lead on the cardboard.



Takes me back to page 2:

Go stand on the bathroom scale. You weight 200lbs (dunno, guessing)
Now put on some shoes 3 sizes too large. You weigh more? (shoe weight aside)

Quick
02-05-2014, 06:13 PM
Go stand on the bathroom scale. You weight 200lbs (dunno, guessing)
I'm on a diet dammit... I'm working towards that.

Now put on some shoes 3 sizes too large. You weigh more? (shoe weight aside)

Right. So the "point" force is 100 (any particular square inch) is psi. If you double the surface area don't you double (assuming it's linear) the *frictional force* assuming you still maintain 100 psi (each square inch has 100 psi) over the entire surface?
With the lead blocks on cardboard you increased the surface area of the card board but held the weight of the lead block constant. So you spread the weight of the lead block over a greater area and there would have been less "point" force or psi at any given square inch on the cardboard.

So I'm thinking all this works out IF the frictional coefficient increases linearly with the force applied (per square inch).

Todd TCE
02-05-2014, 06:36 PM
My only comment on that is that we are throwing around the term "frictional force" again here.

Let's look at that term. Unless I'm wrong (and I'm ok with that) Frictional Force is the force created by the pressure/weight relative to the Mu (http://simple.wikipedia.org/wiki/Coefficient_of_friction) of the surface.

We said we have 25lbs of lead. And we speculated that the cardboard's Cf or Mu to be .15. (ie. slides with relatively little resistance)

So what we have derived is in fact..the frictional force.

Pressure X Area X Mu
We have the same Pressure: 25lbs
We have the same Area: roughly 3 x 5" block of lead
We have the same Mu: .15

Granted the area of the cardboard is greater on the right but the pressure is less per square inch when applied to the concrete. The only way to change the frictional force is to increase the pressure pushing, the area pushing on the cardboard, or the Mu of the cardboard. Remember we're looking to the frictional force between the cardboard and the concrete.

*Taking out any changes relative to temperature here, that's a whole further matter. It can all heat up and cool down.


Point force is interesting. As I described it that's the wear rate in the center of the cardboard we drag across the parking lot. Obviously in both cases we have the same slug of lead. Just like the bending of the pad with a single 2.75" piston.

The problem becomes making the cardboard last. My thought would be to put three 33lb lead weights on the larger part and spread them out equally. Now by equal we still have a square so you can imagine the lower point force is still somewhat limited. What if we put thee 33lbs blocks on a piece that was 8" x 24" long? We could more readily balance that load some. But even so the shape is different but the total force; the same 100lbs For the same reason when we fit pads with multiple pistons the load is factored across the plane of the pad plate to balance both pressure and wear.


Wilwood's own tech info addresses some of this relative to both size and temps:



Q:
Will larger brake pads (http://www.wilwood.com/BrakePads/BrakePads.aspx) improve my stopping distances?


A:
Not necessarily. A larger pad of the same compound in the same location as a smaller pad will not yield shorter stopping distances. The amount of pressure applied, the pad friction coefficient, and the diameter of the rotor at which that pressure is applied, determine the torque reaction, or stopping force. A larger pad does not apply more pressure, only the same pressure over a bigger area.
The size of the pad does matter in terms of heat capacity and wear rate. A larger pad will absorb more initial heat, hence less thermal shock, and have better wear characteristics resulting in longer pad life.

Todd TCE
02-05-2014, 06:58 PM
Getting back to the Jeep for a moment.


Looking at specs on the Jeep I see the 350mm discs come with 48mm pistons. The 380mm discs come with 40mm pistons. *Although I'm puzzled as it shows 4pcs on each application. Can someone correct that? Or is it 40mm x 6?

A 27mm mc is used throughout. They'd need to keep the piston area very close between the two applications for displacement and modulation purposes.

MattRobertson
02-05-2014, 07:13 PM
Wilwood only recently took the W series caliper to the next level of design by incorporating a bridge in the design. Hah that reminds me I converted the two retention pins to bridge bolts for giggles a few years back. Remember that project?

http://www.lxforums.com/board/showthread.php/203805-Wilwood-W6A-caliper-Bridge-Bolt-Conversion

Never had a problem with uneven pad wear then, and four years after doing the mod it hasn't broken anything. I've had less successful projects :-)


Could be early Matt? I did a double-take myself. Thats me alright. That was the very first install with the airflow-y [-]calipers[/-] rotors and the alloy hats. First of two attempts to do 2-piece rotors. First of three if you count the last-try cryo treated set.


So what factors lead you to using the Wilwood W6A, pad choice?As has been pointed out, things were different way back in the Dark Ages. I had an RT with RT knuckles and Todd's Wilwood kits were the only sensible game in town (if you were sponsored or insane you could buy Brembo Gran Turismo for about $6600). The W6A did not exist yet and the BSL6's I fitted used the same pads as the FSL's I put in the back - IIRC that pad is known as a 4 3/4" Stock Car pad. I just had to use thinner versions in the front but they'd work fine in the back. As you can tell from the name, the pad was in use in many racing applications across many platforms and as such a wide variety of pads (mostly useless, it turned out thanks to curb weight) were available from numerous manufacturers. This was important as there was no track record on pad choices so I needed to be able to try out *whatever* and when I found a pad wasn't cut out for the fronts I would typically use it to dial up the rear in conjunction with whatever new and badder-ass pad was up front.

It was clear the BSL6 was adequate but overmatched for tracking the car. You could make it work but really it was a street upgrade on such a heavy car. When the W6A came out it was clear what the upgrade path was simply from the standpoint of survivability. I won't get into the (posted here) details of measuring heat in and on the calipers, fluid boiling etc. etc. It was just clear that we needed a bigger boat. Since I still had RT knuckles on, and an SRT caliper system would require replacement knuckles on front AND rear they were still a much higher cost option than just upgrading to the W6A's... especially since I sold the BSL6's.

Today, the FSL rears were replaced with BSL 4's to enable me to handle SRT rear rotors (I should have done W4A's but I don't think they were around then) and I sprung the coins to buy knuckles (and new hubs). I don't regret having the Wilwood option one bit because imho I still have excellent pad choices (H pads front and rear now... no rotor cracking; no fluid boiling). A 4-wheel Wilwood kit with RockAuto SRT-spec rotors should cost about what a Brembo takeoff system does, except its all brand new and doesn't require swapping around major suspension components to install. For RT owners its still the better choice. For SRT guys I think you already have the tools you need for performance and the decision is about what you want the car to look like.

Todd TCE
02-05-2014, 07:33 PM
Your BSL6s are still in service on another car here I believe. I was a bit leery on that but they seem to be working ok still some seven years later.

I know you're eyeing that 'brake porn' aren't you? But you'd have to sell the car to buy two calipers! lol

bobsmyuncle
02-05-2014, 08:50 PM
.

[still trying to get a firm grasp on this part]

Let's say 1 sq. inch of surface with 100 psi will provide the same frictional force of 2 sq. inches of surface with 50 psi.

This would have to be based on the CF being linear to the psi applied to it. Is that the case?


If you refer to the link I provided earlier it should clarify for you. Things to consider that may help you understand;

-Cf is derived through experiment not mathematics.

-That number is a constant regardless of surface area. You can accept that truth of physics, or get on youTube and watch a bunch of people explain it like I did LOL.

-In your (and others') conceptualizing of the cardboard you (they) are incorporating the deflection of the weight (or force) applied on the sheet of cardboard. A more accurate example would be a force on a plate of sheet plate covering a sheet of cardboard. Immediately you will make the connection to a brake pad right?

-The plate could be 1 inch plate if you like, to convince you that there will be no deflection.

I'll try to find some other graphics to explain it visually.





IIRC that pad is known as a 4 3/4" Stock Car pad.

Correct


It was clear the BSL6 was adequate but overmatched for tracking the car. You could make it work but really it was a street upgrade on such a heavy car.

Specifically what do you mean here? There (as will be) so much contradictory opinion in this thread, yet you all manage to agree with each other LOL. Joel claims the OEM Brembo is adequate, the BSL6 can't be worse can it?


Your BSL6s are still in service on another car here I believe. I was a bit leery on that but they seem to be working ok still some seven years later.


You suggested at one point that mine might be Matt's old ones, I'm not sure they are, but if Matt can confirm who they went to I can confirm. If they are they are in fantastic shape. I use the SRT rotor despite your concern, and for whatever reason I have full pad contact on the rotor, no overhang.

bobsmyuncle
02-05-2014, 09:31 PM
Me I'm out of this thread as the original purpose was to discuss the 8 piston mod and the direction of the thread is all useless tech about pad size and width..

I'm off to my machine shop to make it all work but I'll leave you with this..

The WK2 Jeep calipers come up a lot in the conversation as a comparison and poster children of a good braking system........ but...... they are useless to modify in the present form for any vehicle ...other than a WK2 or Durango.

Everybody that have driven the WK2 Jeep says it stops well.. so that being said............

The pad width is 2 1/2 inches wide on a 2 5/8 " inch rotor pad area.........the pistons are 1 1/2 inches in diameter and there are three of them..... if the Brembo engineers are pretty good.. then why did they use a pad width that wide when a pad width narrower is supposedly better as argued in this thread?????

Personally I'd really like to see your continued involvement.

I started this thread, doubting that I would go forward, but now I'm actually leaning the other way. I'll probably do it. And as you and I seem to be the only interested parties, it would be great to trade info.

And for others shaking their heads at me, here is my thinking.

I've decided to throw the Magnum around the road course. So right away that's a stupid idea. ANY other car would be a better choice. And in all seriousness that really should be kept in mind when considering all the other choices made.

Thus far, I've kept a strict policy of building my car with used parts, and parts that I can sell off again if so desired. I have a small fleet of hobby cars, this one was NEVER intended to be one of them LOL. So I decided to make a deal with myself, have fun with it, but don't get to financially wrapped up in the thing.

I'm currently running the BSL6 with SRT rotors on the RT knuckle up front, and OEM Brembos on SRT knuckles in the rear. I bought the rear setup for a steal as the knuckles were singles and not marketable on their own, and the BSL6s were used from a parted out car, and actually I acquired them on a trade.

So now I want dedicated track wheels, as replacing or damaging my 392 wheels would break my heart, and eating up the expensive rubber sucks.

I am grabbing used wheels, and will be using the Continental scrubs. Catch is I need SRT knuckles to use the wheels. Second catch is that if I do that I can't use my callipers any longer.

Well I found the knuckles for a decent prices so the cost of the used wheels and rubber, and knuckles, and calipers will STILL be cheaper than trying to source a set of new wheels (and without rubber) and keeping my RT knuckles. EXCEPT that I need calipers.

So I started reviewing my caliper options. Todd's kit is the fore runner with the Baer coming in second. However I realized that the AMG caliper, if found affordably which I have, and have access to through a connection would be far cheaper, if indeed I could find a cheap rotor, and pads, (though my concern for pads was more in choices not price to be honest.

So low and behold, I've now got proof that the calipers fit an SRT rotor, with minimal effort, and they fit an 18" wheel. Pad choice is still an unknown. Compare the cost of SRT rotors to those used with the other options and I'm ahead of the game as far as rotors too.

From my reading, while a larger rotor is always better, and thus the AMG caliper would benefit from it (as would any setup), I also know that the outboard pad arrangement (on the circumference of the rotor) alone in theory should improve the performance I currently have, and that's good enough for me.

If I can continue using the cheap SRT rotor, and if I can score the cheap calipers as I believe I can, it is nearly a no brainer. At least initially.

If pad choice or cost really sucks, or real world track use isn't what I was hoping for the calipers will still be marketable if only for the street crowd, and I'll easily sell them.

In the meantime, the LX community will benefit from my experiment.

By alls means, if there is a glaring hole in my logic point it out to me before I screw up!

Todd TCE
02-05-2014, 09:41 PM
I'm not sure who it is that has Matts old BSL6s. Could be you. I had to remove a broken brass fitting if I recall. And the new one is not likely to ever be taken out again with out a lot of work...red loctited due to thread damage. Call it best you can do on a used part and figure they're worthy of replacing at the next major service! lol

The problem for Matt (if he will allow me to interject) is that the pads and calipers are simply too small for his needs. The pads were a tad over the edge of the rotor as the caliper is not fit for a 14.25" disc, they are thin and have nearly 20% less cubic inches than the W6A part. That become a heat issue to a degree as some point out as well as a highly taxed part under..ahem...extreme use. Any 4700lb wagon on a race track is extreme in my book. The W6A, like the big talked about Jeep parts and others) have more caliper mass and stiffer design criteria. And they are engineered for 14-15" discs.

*Tangent time again. Just because something bolts up doesn't mean it fits. In the case of calipers you have what's called the anulus. This is the arc created by the caliper body (and piston alignment too we call Er). That can lead to a bolt up with pads either over hanging or short of the edge. Radial calipers allow for some adjustment here but you have to have "bridge" clearance no matter what! Try fitting your Charger SRT8 caliper to a 15" disc and see if it works. I'd not be surprised the top and bottom hit the disc before the pad is flush. That's anulus.

In Matts case (or my case as I was the one behind it to a point) we were simply running the caliper well past its intended use. Stressing it out of the world. The fit of the W6A made things more 'normal'. (ah, 4700lb wagon...never mind) Running the math we can easily show that they generate less force for the same pressure due to the piston location (ie. pad height) but a firmer pedal push is all that's needed to fix it.



I'm not sure I'd say Cf is derived through experiment vs math. That might be a stretch for those who know more than any of us do. But if you're going to compare apples to apples you'd need to use the same formula for cause and effect. Things like the bias calculators do that quite well. Yes I could have added a backing plate to the cardboard but I'm not sure that's needed for the simplest of visuals. You're right tho: less cardboard shred on the ground if we drag it!


**Reading your second post: I'm not in any way trying to talk anyone out of or into anything here. I'm openly sharing info with you from the big brake world that 99% of anyone else wouldn't give you the time of day on. A lot of this crap is considered 'proprietary' info. I say BS. It's just math and some common sense.

Quick
02-05-2014, 09:57 PM
-Cf is derived through experiment not mathematics.

I understand a material will have a Cf. I was asking if the increase in "stopping power" increases linearly with the force applied to it.
Can I assume that if I double the pressure that I double the "braking force"?


alright, fine, I'll go read the link. ...It's like conceding and reading the manual.

bobsmyuncle
02-05-2014, 10:34 PM
I'm not sure I'd say Cf is derived through experiment vs math. That might be a stretch for those who know more than any of us do.

This isn't my opinion, I have read this several times. Literally of course, everything is figured out mathematically but in real life, testing determines Cf.

...Yes I could have added a backing plate to the cardboard but I'm not sure that's needed for the simplest of visuals. You're right tho: less cardboard shred on the ground if we drag it!

Some are looking at this like they would walking on snow. In deep snow, wearing boots you sink (small contact patch), wearing snow shoes (large contact patch) you stay on the surface. That analogy doesn't work in this topic of conversation. I was looking for a way to show that the piston doesn't affect the contact area (or more specifically the Cf) of the friction surface.

**Reading your second post: I'm not in any way trying to talk anyone out of or into anything here. I'm openly sharing info with you from the big brake world that 99% of anyone else wouldn't give you the time of day on. A lot of this crap is considered 'proprietary' info. I say BS. It's just math and some common sense.

No worries, I appreciate the input far more than you probably realize. I'm not looking for coddling here, my mom didn't design the AMG caliper so I have nothing invested LOL.

I'm not looking for bling, I'm looking for a sensible (balance of cost, effort, and performance) option based on my needs (or potential needs to be accurate). As I said if going forward is a mistake, I'm hoping this thread will expose that.

Todd TCE
02-05-2014, 11:44 PM
I understand a material will have a Cf. I was asking if the increase in "stopping power" increases linearly with the force applied to it.
Can I assume that if I double the pressure that I double the "braking force"?


alright, fine, I'll go read the link. ...It's like conceding and reading the manual.

Four things increase brake torque.
1. Push harder on the pedal. Line pressure.
2. Increase piston AREA. More clamping for same line pressure.
3. Bigger diameter rotors. Larger lever arm.
4. Higher Cf pads. Greater bite.

All that aside, shorter stopping distance? Try a more sticky tire.

bobsmyuncle
02-06-2014, 12:44 AM
I understand a material will have a Cf. I was asking if the increase in "stopping power" increases linearly with the force applied to it.
Can I assume that if I double the pressure that I double the "braking force"?


alright, fine, I'll go read the link. ...It's like conceding and reading the manual.

Yeah I mentioned that as a reminder to anyone not clear on it.

Quick
02-06-2014, 12:47 AM
Got it. I was asking if (1) brake torque is directly proportional to line pressure. hold 2,3, and 4 constant, if you double line pressure do you double brake torque?

Any link with the cliff notes for the equations to those? (ok, forget about 3, that's probably going to be a really long equation :))

Todd TCE
02-06-2014, 10:18 AM
Got it. I was asking if (1) brake torque is directly proportional to line pressure. hold 2,3, and 4 constant, if you double line pressure do you double brake torque?

Any link with the cliff notes for the equations to those? (ok, forget about 3, that's probably going to be a really long equation :))


Of course. Think of it as torquing a bolt: you use the same wrench and apply more grunt, you get more torque. You prove it to yourself every day. Drive to a stop sign and lightly drag the brake pedal (low pressure) did you stop? What happened when you pushed harder? (more pressure)

Use either one of the calculators and watch what happens when you increase 'leg'. You'll see the line pressure go up of course and that will transfer to the rotor torque value directly. In fact you can see cause and effect on any of the variables by changing them: Leg, piston size, pad size, rotor size and pad Cf. An in this one here you can vary the pedal ratio and offset the bias in a dual mc set up to alter the bias. And you can match it to the demands of the car via the accompanying weight shift calculator. And did you guys realize that tire size changes this also? We keep talking "rotor torque" as it's what we measure, but the reality is what we feel is "tire torque".

MC CALC. (http://www.tceperformanceproducts.com/dual-bias-calc/)


** A friend of mine I was talking to recently about this (the pad size issue) brought up a very good point. If all one had to do was install a larger pad in a car don't we think the market would be flooded with such products for cars now? Like the magical drilled rotor on ebay. "Exclusive Power Pads add 15% more pad material for improved braking performance" "Engineered to fill the gaps in calipers and unswept rotor areas our pads increase braking power, wipe clean rotors and lower wear rate"....you get the idea. Thought it was an interesting spin.

MattRobertson
02-06-2014, 12:46 PM
Specifically what do you mean here? ... Joel claims the OEM Brembo is adequate, the BSL6 can't be worse can it?
Well in addition to Todd's comments which I agree with completely - the parts that I understand at least - one very clear sign of a caliper out of its depth was the heat it was suffering. I was reading enormous temperatures in the caliper (maxed out and melted the heat stickers I put on so had to resort to a laser) and as one of the old-timers here you remember I am sure how I was literally bleeding out black fluid from a system that almost let my pedal fall to the floor... and I was using titanium spacers (but not the insulated pistons) and fan-fed brake ducts. They just got too hot. I had taken them as far as they can go (although I *could* have done one more thing: ditch the Wilwood 575 fluid and go to the EXP... but from experience I'd say that was unlikely to truly solve the problem.

Joel's experience says the BSL6 is not as good as the Brembo calipers at this extreme. When Joel claims X associated with racing the car, he's the guy who would know better than any of us. We aren't talking track days thats real racing... NOW with that said he's racing a much lighter car, and weight is dam near everything, but still I'd take his word on it, just as I do Todd when he starts getting into all that math stuff about piston size and pad friction and whatever... the guy does this for a living AND he races stuff.

Those Carbotech pads can actually be too strong for the car. Don't want to steal someone's thunder so I'll just say I know of one person who used a compound they had that was actually too good for our cars. The brakes survived as did he and his car.

Now, I do understand your value calc when it comes to using those Benz calipers. Its hard to turn away from them. BUT don't look at this as a purchase. Look at the maintenance. If the consumables can work for you (pads) and not break the bank (pads and rotors) then and only then do it.

And STILL nobody has followed up on my mention of the weight difference on these calipers/rotors. Together ain't that something to take into account (probably not on the Jeep as they are doing it now stock and its even more of a tank than an Lx)?



You suggested at one point that mine might be Matt's old ones, I'm not sure they are, but if Matt can confirm who they went to I can confirm... I am going nuts right now cuz I can't remember his screen name. He's one of the old timers, is not around anymore I think. He had an AWD Magnum and his avatar was a Cessna logo. Was from back East. Connecticut I think. He and Ron380 ran together. I'm going to feel like an idiot when someone tells me the name. Interesting about the damage Todd referenced on the caliper. That doesn't sound like mine at all. As far as I know they were undamaged and even were still in good shape despite the heat cycling. They needed piston rebuilds but that was a given at time of sale.


and for whatever reason I have full pad contact on the rotor, no overhang.That is one thing Todd mentioned that he got wrong. Too much time has gone by. The calipers shimmed right up (after a fair number of shims and effort to get them just right) dead center and onto the edge of the pad. I only used them like that for a short time.

bobsmyuncle
02-06-2014, 01:27 PM
Not Hawkxp?

Nope as soon as I saw his avatar I knew I was wrong.

It has 4 letters doesn't it? Maybe TSSA?

Hemissary
02-06-2014, 08:13 PM
I am going nuts right now cuz I can't remember his screen name. <snip>

Ya got me think'in about it...that's TTMR :^)

bobsmyuncle
02-08-2014, 12:31 AM
That's it, gotta be!

Blown7
02-08-2014, 12:07 PM
I know I said I was out but I couldn't resist when I found the patent Brembo had for the 8 piston calipers

Picture here.. http://www.freepatentsonline.com/6722476.html



EP0905404



Brake caliper with cooling installation


JP8226466






Primary Examiner:
Lavinder, Jack

Assistant Examiner:
King, Bradley T.

Attorney, Agent or Firm:
Hogan & Hartson LLP


Claims:
What is claimed is:

1. A caliper for a disk brake for motorcars, said caliper comprising a body having two side portions and two transverse bridges connecting the two side portions, cylinder-piston units arranged along each side portion, and a circuit with an inlet and an outlet for a fluid for cooling the cylinder-piston units, wherein the circuit for the fluid for cooling the cylinder-piston units comprises wells formed along at least one of the side portions, the wells being of a depth such that they extend to a wall proximate to and delimiting at least one of the cylinder-piston units, the wells being closed by covers, at least one of said covers bearing an appendage extending into a respective well in order to occupy a predominant portion thereof, and the circuit also comprising connecting ducts for putting the wells into fluid communication with one another.

2. The caliper according to claim 1, wherein each of the covers bears an appendage extending into respective wells in order to occupy predominant portions thereof.

3. The caliper according to claim 1, wherein the appendage of said at least one cover comprises a deformation of the cover.

4. The caliper according to claim 1, wherein the covers and the appendage are made of aluminum.

5. The caliper according to claim 1, wherein the body is formed by mechanical machining from a solid semi-finished product made of aluminum alloy, and in that the wells and the ducts are produced by milling and by drilling, respectively.

6. The caliper according to claim 1, wherein said circuit for the fluid for cooling the cylinder-piston units comprises wells formed along both of said side portions.

7. The A caliper according to claim 1, wherein portions of boundaries defining said wells concentrically follow a periphery of said cylinder-piston units.

8. The caliper according to claim 1, wherein said at least one of said covers bearing said appendage is adapted such that said appendage follows the contour of a boundary defining said respective well.

9. The caliper according to claim 1, comprising four of said cylinder-piston units on each side portion.

10. The caliper according to claim 1, wherein at least one of said wells extend into a space located substantially between adjacent ones of said cylinder-piston units.

11. The caliper according to claim 1, comprising three of said covers on each side portion, and wherein a middle one of said three covers on each side portion bears an appendage extending into a corresponding well in order to occupy a predominant portion of said corresponding well.

12. A caliper for a disk brake suitable for automobiles, said caliper comprising a body having two side portions and two transverse bridges connecting the two side portions with cylinder-piston units arranged along each side portion, and a circuit with an inlet and an outlet where said circuit is adapted to carry a fluid for cooling said cylinder-piston units, wherein said circuit comprises wells formed along at least one of said side portions, said wells being of a depth from a surface of said side portions such that said wells are at least partially defined by an inner wall, said inner wall being proximate to at least one of the cylinder-piston units and being substantially concentric to said proximate cylinder-piston unit, said circuit comprising ducts for putting said wells into fluid communication with one another, and wherein said wells are sealed closed with covers with at least one of the covers bearing an appendage extending into a corresponding well in order to occupy a portion thereof.

13. The caliper according to claim 12, wherein said appendage is shaped to complement said inner wall.

14. The caliper according to claim 12, wherein each of the covers bears an appendage extending into a corresponding well in order to occupy a portion thereof.

15. The caliper according to claim 14, wherein said appendages are shaped to complement said inner wall.

16. The caliper according to claim 12, wherein at least one of said wells extend into a space located substantially between adjacent ones of said cylinder-piston units.

17. The caliper according to claim 16, wherein said at least one well extending into said space has two inner walls, each wall corresponding to one of an adjacent pair of cylinder-piston units such that said well is substantially cusp-shaped.

18. A caliper for a disk brake for motorcars, said caliper comprising a body having two side portions and two transverse bridges connecting the two side portions, cylinder-piston units arranged along each side portion, and a circuit with an inlet and an outlet for a fluid for cooling the cylinder-piston units, wherein the circuit for the fluid for cooling the cylinder-piston units comprises wells formed along at least one of the side portions, the wells being of a depth such that they extend substantially as far as the vicinity of one or more walls delimiting at least one seat of the cylinder-piston units, at least one well having a space fitted between adjacent cylinder-piston units, and the wells being closed by covers, at least one of the covers bearing an appendage extending into a corresponding well in order to occupy a predominant portion thereof, and wherein the circuit also comprising connecting ducts for putting the wells into fluid communication with one another.

19. The caliper according to claim 18, wherein said at least one well extending having said space is partially defined by two inner walls, each wall corresponding to one of an adjacent pair of cylinder-piston units such that said well is substantially cusp-shaped.

20. The caliper according to claim 18, wherein said appendage is shaped to complement said one or more walls.



Description:
BACKGROUND OF THE INVENTION

The present invention relates to a caliper for disk brakes for motorcars, particularly high-performance cars, of the type comprising a body having two side portions and two transverse bridges connecting the two side portions, cylinder-piston units arranged along each side portion, and a circuit with an inlet and an outlet for a fluid for cooling the cylinder-piston units.
As is known, in calipers of the type specified, it is necessary to cool the cylinder-piston units so that the braking fluid does not reach excessively high temperatures which would lead to boiling of the braking fluid and consequently to loss of braking efficiency.
In known calipers, although the circuits for the cooling fluid used up to now for preventing the braking fluid from reaching excessively high temperatures are substantially satisfactory, they have recognized disadvantages.
For example, there are known calipers which have cooling-fluid circuits constituted by ducts formed in the caliper body during casting. These ducts extend along the side portions of the caliper and their path extends past the walls of the cylinder-piston units. However, this known solution requires the caliper bodies to be produced by casting with the disadvantage of structural complexity of the body.
Calipers which have fluid ducts, particularly air ducts, which extend along the cylinder-piston units in the vicinity of the region of contact with the braking pads have also been proposed. However, this latter solution is penalized by the poor heat-removal capacity typical of air, and requires very large ducts.
The technical solution of fitting, on the caliper body, elements having ducts through which a cooling liquid, rather than air, is intended to flow, however, have the disadvantage of requiring dimensions which are notably large, although smaller than those of solutions in which the cooling fluid is air.
SUMMARY OF THE INVENTION

The problem upon which the present invention is based is therefore to devise a caliper of the type specified which has structural and functional characteristics such as to satisfy the above-mentioned need to cool the cylinder-piston units, at the same time overcoming the disadvantages mentioned with reference to the prior art.
This problem is solved by a caliper of the type specified which is characterized in that the circuit for the fluid for cooling the cylinder-piston units comprises wells formed along at least one of the side portions, the wells being of a depth such that they extend substantially as far as the vicinity of the wall delimiting at least one of the cylinder piston units, and the wells being closed by covers, the circuit also comprising connecting ducts for putting the wells into fluid communication with one another.
BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and the advantages of the caliper according to the present invention will become clear from the following description of embodiments thereof given by way of non-limiting example and illustrated in the appended drawings, in which:
FIG. 1 is a view showing a first embodiment of the caliper according to the invention, in longitudinal section,
FIG. 2 is a perspective view of the caliper of FIG. 1 with parts separated, viewed substantially from below and from the rear,
FIG. 3 is a perspective view of the caliper of FIG. 1 with parts separated, taken from above and from the rear,
FIG. 4 is a perspective view of the caliper of FIG. 1, with parts separated, taken from above and from the front,
FIG. 5 is a shows a variant of the caliper of the preceding drawings, in longitudinal section,
FIG. 6 is a perspective view of the caliper of FIG. 5, taken from below.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to the appended drawings, a caliper for a disk brake intended for a motorcar in general and for a high-performance motorcar in particular, is generally indicated 1.
The caliper 1 comprises a body 2 produced by machining from a solid semi-finished product, for example, from a rolled piece or from a forging of a suitable aluminium alloy known per se.
The body 2 has opposed elongate side portions 3 and 4 which are intended to be arranged along opposed sides of a braking band of the disk of a disk brake, not shown in the drawings.
The side portion 3 is disposed on the inner side and the side portion 4 is disposed on the outer side of the disk, in conventional manner.
Each of the side portions 3 and 4 has a lower peripheral wall 3a, 4a and an upper peripheral wall 3b, 4b.
Two transverse connecting bridges 5 and 6 connect the two side portions 3 and 4 to one another at their respective ends and on the side with the peripheral walls 3b and 4b. These connecting bridges 5 and 6 extend over the braking band of the disk.
The caliper 1 is of the fixed type and is intended to be fixed to an axle of the motor vehicle in conventional manner.
Cylinder-piston units are arranged along each of the two side portions 3 and 4. In the embodiment illustrated, four cylinder-piston units 7, 8, 9 and 10 are disposed in the side portion 3 and four cylinder-piston units 11, 12, 13 and 14 are disposed in the side portion 4.
The respective cylindrical seat of the cylinder of each cylinder-piston unit 7-14 in which the respective piston, not shown, can slide, is indicated 7a-14a.
A fluid circuit 15 for a braking fluid supplies all of the cylinder-piston units in conventional manner known per se.
According to the present invention, the caliper 1 comprises a fluid circuit 16 for a cooling fluid, for example water, which is provided for cooling the cylinder-piston units 7-14 and, more precisely, for cooling the braking fluid operating therein, in order to avoid the danger of boiling of the braking fluid.
The fluid circuit 16 for the cooling fluid has a path 17 which extends between two connectors 18 and 19 which constitute the inlet and the outlet for the cooling fluid.
Wells are formed in the lower walls 3a and 4a of the side portions 3 and 4, preferably by mechanical milling with machine tools. More precisely, according to the embodiment shown in FIGS. 1-4, three wells 20, 21, 22 and 23, 24, 25, respectively, are formed in each side portion 3 and 4, each in a position between respective adjacent cylinder-piston units.
Each well 20-25 has a substantially cusp-shaped end 20a-25a fitted between the respective adjacent cylinder-piston units so that the ends 20a-25a of the wells are close to the walls delimiting the cylindrical seats 7a-14a and hence are in a good heat-exchange relationship therewith.
The wells 20-25 are closed in a leaktight manner by respective covers 20b-25b, for example, by means of conventional screws, or by snap-closure means, or even by gluing, leaktightness being ensured by respective seals 20c-25c.
The well 21 and the well 24, which are deeper, are closed by the covers 21b and 24b. These have appendages 26 and 27 which project into the respective wells 21 and 24 defining respective spaces 28 of limited transverse dimensions.
The wells 20 and 21, as well as the wells 23 and 24 are in fluid communication with one another by means of respective ducts 29. The wells 21 and 22 as well as the wells 24 and 25 are in fluid communication by means of ducts 30.
The ducts 29 and 30 are produced by drilling along two intersecting axes.
The well 22 is put into fluid communication with the well 25 by means of a conventional duct, not shown, and the well 23 is put into communication, by means of a further duct, not shown, with a threaded hole 31, opening into the inner side of the side portion 3. The connector 19 is screwed into the threaded hole 31 on the outside of the caliper. A threaded hole 32 is formed in the cover 20b. This hole 32 which, in practice, is on the outside of the caliper in the same manner as the threaded hole 31, houses the connector 18 which is screwed therein.
It is clear at this point that the circuit 16 for the cooling liquid is constituted by the spaces 28 formed by the covers 20b-25b with the ends of the respective wells 20-25, by the ducts 29 and 30, and by the transverse connecting ducts (not shown) which put the well 22 into communication with the well 25 and the well 23 into communication with the threaded hole 31.
All of the covers 20b-25b are made of aluminium. The appendages 26 and 27 formed integrally with the respective covers 21b and 24b are also made of aluminium.
In operation, the cooling fluid which passes along the path 17 of the circuit 16 flows through the ducts, close to the cylinder-piston units, ensuring that the temperature of the braking fluid is kept below its boiling points.
With reference to the embodiment of FIGS. 5 and 6, it will be noted that the circuit for the fluid for cooling the cylinder-piston units comprises, for each side portion 3 and 4, two wells, indicated 33 and 34, closed by respective covers 33b and 34b with seals 33c and 34c. The wells 33 and 34 of the side portion 4 are shown in FIG. 6 without the respective covers. The ends 35 and 36 of the well 33 and of the well 34, respectively, are shaped so as to be close to the peripheral walls of the cylindrical seats of the cylinder-piston units and the respective covers 33b and 34b are shaped, for example, by drawing, so as to reproduce the shapes of the ends 35 and 36. A space 37 formed between the covers 33b and 34b and the ends 35 and 36 of the respective wells constitutes part of the circuit for the cooling fluid.
The connectors 18 and 19 which, in the embodiment of FIGS. 5 and 6, are indicated 18a and 19a, are advantageously positioned in the vicinity of the centreline xx of the caliper.
The main advantage of the caliper according to the present invention lies in its reliability, as well as in maximum strength.
Naturally, in order to satisfy contingent and specific requirements, an expert in the art may apply to the above-described caliper many modifications and variations all of which, however, are included within the scope of protection of the invention as defined by the following claims.

Todd TCE
02-08-2014, 02:46 PM
That's a pretty cool find. Not sure I follow all that language on it but it makes for an interesting read.

53249

One thing I might mention when you fit them up is that you might want to tip the calipers (or vehicle) a bit to purge all the air. One of the inherent problems with such calipers (think that 12 pot for sure) is that you don't have a straight line on the bleed port. When the caliper is in it's vertical position you'll note the bleed passages are a tad 'over center' in which case air can become trapped in the resulting crown. Even a bit of air in there will have a compression effect. Depending upon how the calipers are mounted (in front or behind the disc centerline) you an raise or lower the vehicle some to angle the caliper to help purge it.

Blown7
02-08-2014, 03:59 PM
That's a pretty cool find. Not sure I follow all that language on it but it makes for an interesting read.

53249

One thing I might mention when you fit them up is that you might want to tip the calipers (or vehicle) a bit to purge all the air. One of the inherent problems with such calipers (think that 12 pot for sure) is that you don't have a straight line on the bleed port. When the caliper is in it's vertical position you'll note the bleed passages are a tad 'over center' in which case air can become trapped in the resulting crown. Even a bit of air in there will have a compression effect. Depending upon how the calipers are mounted (in front or behind the disc centerline) you an raise or lower the vehicle some to angle the caliper to help purge it.

You've got a point there, I guess pressure pot bleeding from the caliper up would be better...

Todd TCE
02-08-2014, 05:03 PM
But my hair hides it well.

Not an uncommon problem that has folks stumbled at times. Normally when the passage is drilled off crown center they also mill a small swipe step in the edge of the bore to try and compensate for this. It allows for 'some' angularity but not a lot.

bobsmyuncle
02-09-2014, 12:01 PM
You've got a point there, I guess pressure pot bleeding from the caliper up would be better...

Not sure I follow "from the caliper up" would you mind clarifying that for me?

Blown7
02-09-2014, 12:43 PM
Not sure I follow "from the caliper up" would you mind clarifying that for me?

http://www.e38.org/brake_bleeding.htm

and starting at the caliper can be done like we do on aircraft

http://lancair.net/lists/lml/Message/46118.html?Language

Blown7
02-09-2014, 12:51 PM
You do know what this means .. don't you??

http://i25.photobucket.com/albums/c96/Blown7/20130513_011114_zps98432e29-1.jpg (http://s25.photobucket.com/user/Blown7/media/20130513_011114_zps98432e29-1.jpg.html)

Todd TCE
02-09-2014, 02:32 PM
That it fits a 15" disc? (you need an air gap in the bridge)

Blown7
02-09-2014, 02:52 PM
That it fits a 15" disc? (you need an air gap in the bridge)

That template is 15.400 " so even with a 15" rotor you still have a little less than 1/4" of an inch for a gap, some of the MB guys run as little as 2 Millimeters for clearance.

So it will fit the Jeep WK2 rotors diameterwise, now if all the offsets are correct the OEM rotor could work, and gives the option of some rotor manufacturer to manufacture a kicka$$ 2 peice rotor that could be sold to the Jeep WK2 aftermarket or a retrofit for this modification.

Now who could make a kicka$$ two piece lightweight Aluminum hat, floating Jeep WK2 rotor for the blinging crowd rather inexpensively??

The AMG rotor is using a stock rotor width of 36 Millimeters which is more than anything being offered out there OEM wise.

Blown7
02-09-2014, 03:31 PM
Now lets go in another direction... on guy claimed on a message board that he got the equivalent of 10 horsepower increase from lighter 2 piece rotors ...per wheel, mileage increased, acceleration increased, stopping distance decreased.. lots of claims...

Any one know otherwise?


.

Blown7
02-09-2014, 03:54 PM
Like this only cheaper..

http://www.racingbrake.com/Two-piece-rotor-Open-Slot-Jeep-Grand-Cherokee-p/2316.htm

And if the weight reduction argument hold true these should pay for themselves in better fuel economy.


.

Todd TCE
02-09-2014, 04:01 PM
I wouldn't push it beyond 15". At 15.4 you have but .200" air gap. (the radius not the diameter for those not following this)

The reality is that 'fit' is the pad flush to the edge of the disc. Rotors larger than that don't do you and good, rotors smaller than that have pad overhang issues.

If you're bolting it up the bolt it in place and measure the net radius to the spindle. X2 and you have your diameter. Not totally easy to do so you can spec your mount height on the caliper and then the mount height on the spindle, add them together and X2 if you like.



Sure, I can make you up some 2pc hats and rotors that are 15". And you might find some from Baer or Stoptech or others. You'll need the full spec on them:

Hat:
Diameter
Center bore
Offset
Mount circle
Mount size
Mount type
Mount quantity
Face thickness
Stud circle
Stud diameter

Rotor:
Diameter
Width
Eye
Bolt Circle
Bolt Quantity
Bolt diameter
Flange diameter

Having done more than a few of such things over the years..your idea of affordable may not be the same, but I'd say most parts like this will run you anywhere from $900 bare bones to $1100 per set. Add some bling- slots, holes, plating..add another $100-150. Make them floating not fixed and you can factor another $200 due to the buttons and machining needs. And they will rattle on you in due time is not uncommon.


I'd say there are some gains in HP yes. But compare apple and apples. If you go from 14" to 15" just because the center is alum is no promise of great weight savings. And it plays huge roll in inertia calculations. AND you go from 1.25" to 1.40" wide? That's weight. Why? Because most rotors this size are spe'd in the 1.375-1.500" range.

Did he mention such large discs and their inertia also play a roll in handling? Try changing direction of a spinning object. Now increase that objects weight and diameter. It's far harder to turn. Rotors that are heavy don't like to turn. Steering input is greater as is resistance. Part of the reason for carbon rotors.

*Remember those spinning things with handles on them from the gym as a kid? Your spun them and held them with both hands. Then you swayed from side to side turning them feeling that sensation between your wrist. That's inertia. Not make that wheel bigger and heavier.

Blown7
02-09-2014, 04:16 PM
True that but now figure the gains of a 14 inch rotor weight wise and inertia wise and a 15 in weight and inertia and the 14 will probably come out on top.
I believe NASCAR has found the 14.5 inch rotors have the best compromise.

My argument about the big price tag is...if .6 MPG increase of gas can be achieved with lighter rotors for me I'm saving roughly about $220 dollars a year in fuel and your going to make me some real good rotors for $800 a set that will take 4 years for a payback.

Well Racing Brake claims a 8 pound saving per rotor and a unsprung weight saving is roughly equal to a 4 times multiplier... so in effect by adding two piece rotors that should be good as removing 64 pounds of weight from the vehicle just by changing front rotors...

Now my buddy Builder Bill is considering a lighter 2 piece rotor in his Monster Jeep.... what will his better 1/4 mile time/speed be?
Or the advantage of cornering on a course??

I'm not a engineer but these things need to be considered.


.

Blown7
02-09-2014, 04:36 PM
For Todd.....
As for all the dimensions you listed earlier you would use the factory OEM Jeep WK2 rotor dimensions, just making a lighter two piece rotor from those measurements.

Plus your going to be able to sell these two piece rotors to the regular Jeep SRT WK2 guys cause your reasonably priced and you have a much bigger market....

Blown7
02-09-2014, 04:45 PM
This thread reminds me of Silvio in the Sopranos... "Just when I thought....." "they pull me back in"

I'm out again.


.

Blown7
02-09-2014, 05:15 PM
Great read going on the Porsche forum about Brembo brakes

http://forums.rennlist.com/rennforums/991-gt3/789748-the-porsche-brake-caliper-conspiracy.html

Todd TCE
02-09-2014, 07:13 PM
The term I was looking for it "Gyroscopic effect" which is elevated by both bigger wheels and tires as well as discs.

Most NASCAR type rotors are in the 12.9" range but upwards of 1.625" thick. They still run 15" wheels. The goal here is to have the largest heat sink they can.

As for manufacturing 2pc rotors...I'll be happy to help anyone who's interested. Am I planning a run of such monsters for 'the market'? Not on your life. The likelihood of selling such parts is so remote it's money tied up on a shelf. Any such thing would be on a per order basis or a minimal run of them for a group buy deal. When you start talking $1000+ for a pair of rotor it's a pretty small market!


*That bridge bolt or no bridge bolt is part of the ongoing debate over caliper deflection. Keeping the body stiffer with with the bars as part of the caliper would make the most strength. Long open sections the least strong.

Blown7
02-10-2014, 06:17 AM
As for manufacturing 2pc rotors...I'll be happy to help anyone who's interested. Am I planning a run of such monsters for 'the market'? Not on your life. The likelihood of selling such parts is so remote it's money tied up on a shelf. Any such thing would be on a per order basis or a minimal run of them for a group buy deal. When you start talking $1000+ for a pair of rotor it's a pretty small market!




Yea well I just thought I'd throw that out there as a suggestion for you......... I can make my own.

Todd TCE
02-10-2014, 10:25 AM
Any time I do so oddities and supersized parts it a case by case basis. The cost of holding back stock is just too great. If you can make them tho then you should be able to sell them to others and essentially get yours paid for I assume would be the plan. Certainly the preferred method.


Found the old notes on the SRT8 Rotors. They were 14.19" dia and 1.260 wide. Fit with 8 bolt Wilwood aluminum hats they sold for about $850pr.

When you go to a 15" rotor tho the casting requirement changes and the price goes up. The good thing tho is that the hat size can also increase. I'm not keen on a 14.25" disc on a 7" bc hat.

Theblackone
02-10-2014, 10:33 AM
Like this only cheaper..

http://www.racingbrake.com/Two-piece-rotor-Open-Slot-Jeep-Grand-Cherokee-p/2316.htm

And if the weight reduction argument hold true these should pay for themselves in better fuel economy.


.

I guess cheaper $$ would be these ones: http://www.lxforums.com/board/showthread.php/347698-SRT8-2-Piece-Lightweight-Stock-Replacement-Rotors-Coming!

Todd TCE
02-10-2014, 02:57 PM
Found the old notes on the SRT8 Rotors. They were 14.19" dia and 1.260 wide. Fit with 8 bolt Wilwood aluminum hats they sold for about $850pr.

When you go to a 15" rotor tho the casting requirement changes and the price goes up. The good thing tho is that the hat size can also increase. I'm not keen on a 14.25" disc on a 7" bc hat.



I think I made up about three sets of these about five years ago.

Blown7
02-10-2014, 03:11 PM
I guess cheaper $$ would be these ones: http://www.lxforums.com/board/showthread.php/347698-SRT8-2-Piece-Lightweight-Stock-Replacement-Rotors-Coming!

Yea not really that bad...... preordered at $723 dollars for fronts in a 15 inch... now that is a price point that this stuff should be selling for.

Maybe I'll order some for the hell of it.



.

MorePower4me
02-10-2014, 05:54 PM
I have nothing terribly useful to add to this thread or the analysis therein (although interesting) - but I went through the exercise on a few other cars and the 'sweet spot' caliper I found was the Touareg/Cayenne caliper. 6 Pistons, Brembo, monobloc, cheap & plentiful.

I stole the idea from here - http://www.nsxprime.com/forum/showthread.php/77212-Project-Custom-Big-Brakes? - One of the smartest internet forum posters I've found, you should see some of his other threads!

http://www.imagdesigns.com/images/DSCF0871sm.jpg

I hope that helps!

MattRobertson
02-10-2014, 08:01 PM
Ah the big Cayenne calipers are *big*! Forgot all about them. Nice find. I wonder how they compare.


Ya got me think'in about it...that's TTMR :^)

*doh*

Yep thats him. Thx!

Todd TCE
02-10-2014, 09:03 PM
Ah the big Cayenne calipers are *big*! Forgot all about them. Nice find. I wonder how they compare.




I find them to be 34,36,38mm bores.

1.34, 1.42, 1.50

4.72sq" total.

Pretty much back to that same roughly 4.8" we have in the SRT8.

VW mc bore: 27mm (1.063")

SRT8 bore 1.063


Transfer them to the SRT8 with the same rotor size: same braking.

knownman
02-11-2014, 01:16 AM
Although I'm nowhere near as crazy as you all are I do enjoy a good read. And I can say this has been a good nights read so thanks for the insight.

now if I was wanting to do a slight upgrade in rotor and pad for my street driven supercharged SRT Challenger....

any suggestions?

thanks in advance,

Hemissary
02-11-2014, 01:30 AM
Plenty of folks here to help you with dat, but you bring up an extremely valuable point that few ever think about....



...all the effort to make a car go quicker / faster and zero thought put into making it slow down just as well...and I'm not talking about a road course either :^/

Blown7
02-11-2014, 07:36 AM
I have nothing terribly useful to add to this thread or the analysis therein (although interesting) - but I went through the exercise on a few other cars and the 'sweet spot' caliper I found was the Touareg/Cayenne caliper. 6 Pistons, Brembo, monobloc, cheap & plentiful.

I stole the idea from here - http://www.nsxprime.com/forum/showthread.php/77212-Project-Custom-Big-Brakes? - One of the smartest internet forum posters I've found, you should see some of his other threads!



I hope that helps!

I got something even better... but I can't post it yet as i promised someone a heads up first as he helped me and I want him to make his purchases unhindered and before the prices start exploding and all the cool kids catch on..





.

Blown7
02-11-2014, 07:40 AM
Well the AMG pads minus a couple small undercuts are the same basic area size as the WK2 pads

http://i25.photobucket.com/albums/c96/Blown7/BrakeBremboupgrade063.jpg (http://s25.photobucket.com/user/Blown7/media/BrakeBremboupgrade063.jpg.html)

http://i25.photobucket.com/albums/c96/Blown7/BrakeBremboupgrade064.jpg (http://s25.photobucket.com/user/Blown7/media/BrakeBremboupgrade064.jpg.html)


Daddy really like, AMG on bottom, WK2 on top.

http://i25.photobucket.com/albums/c96/Blown7/BrakeBremboupgrade065.jpg (http://s25.photobucket.com/user/Blown7/media/BrakeBremboupgrade065.jpg.html)




.

Todd TCE
02-11-2014, 09:26 AM
now if I was wanting to do a slight upgrade in rotor and pad for my street driven supercharged SRT Challenger....



Because we're having an open discussion here on all these parts and how they function etc; What's a "upgraded" rotor mean to you?

Blown7
02-11-2014, 01:48 PM
I find them to be 34,36,38mm bores.

1.34, 1.42, 1.50

4.72sq" total.

Pretty much back to that same roughly 4.8" we have in the SRT8.

VW mc bore: 27mm (1.063")

SRT8 bore 1.063


Transfer them to the SRT8 with the same rotor size: same braking.

You better be clearer,,,,,,,, there are 2 separate SRT8's being discussed here .........Jeeps and Cars.
I think all the First Gen SRT8 brakes are the same on the Jeep and car but I think the Second Gen SRT8's Jeeps and cars are different sizes.

(That changes all your calculations which BTW you assume...... and I'm actually measuring.... and your numbers are wrong.) And no I'm not telling you what the actual numbers are.. buy your own calipers and master cylinders and do your own real reseach.

Plus your assuming all the master cylinders are the same sizes, I don't know if they are... and if they are not..... that would change the length of piston movement. Area of the piston alone is one thing, but you also have to figure the arm length which is a unknown (and I'm not wasting time figuring that) so the actual pedal feel could change substantially between vehicles, and without that being known your throwing out random area numbers and your pedal feel is a wide a$$ed best guess.

knownman
02-11-2014, 02:17 PM
Really a bit aggressive with this one.

Guy is providing sound information with technical documentation to support it.

If you want to contribute why not offer the correct dimensions so that the correct calculations could be discussed?

Just seems like a bone to pick to me.

:ninja:

Blown7
02-11-2014, 02:22 PM
Really a bit aggressive with this one.

Guy is providing sound information with technical documentation to support it.

If you want to contribute why not offer the correct dimensions so that the correct calculations could be discussed?

Just seems like a bone to pick to me.

:ninja:

Yea your right...... I'm leaving again. You can't argue with a vendor who thinks he sells the best parts.

Hemissary
02-11-2014, 02:25 PM
Really a bit aggressive with this one.

Guy is providing sound information with technical documentation to support it.

If you want to contribute why not offer the correct dimensions so that the correct calculations could be discussed?

Just seems like a bone to pick to me.

:ninja:

^^Agreed - selfish pontification comes to mind...

knownman
02-11-2014, 02:30 PM
I don't necessarily agree.

In my mind he hasn't sold me on a single product. Yeah he's given me the opportunity to become a more informed buyer.

What is wrong with that? He's a vendor. So what? He's also actively contributing without throwing other vendors under the buss.

If it makes you feel better go ahead and take your ball with you.
Makes me think of kindergarten.

:roll:

Todd TCE
02-11-2014, 03:02 PM
You better be clearer,,,,,,,, there are 2 separate SRT8's being discussed here .........Jeeps and Cars.
I think all the First Gen SRT8 brakes are the same on the Jeep and car but I think the Second Gen SRT8's Jeeps and cars are different sizes.

(That changes all your calculations which BTW you assume...... and I'm actually measuring.... and your numbers are wrong.) And no I'm not telling you what the actual numbers are.. buy your own calipers and master cylinders and do your own real reseach.

Plus your assuming all the master cylinders are the same sizes, I don't know if they are... and if they are not..... that would change the length of piston movement. Area of the piston alone is one thing, but you also have to figure the arm length which is a unknown (and I'm not wasting time figuring that) so the actual pedal feel could change substantially between vehicles, and without that being known your throwing out random area numbers and your pedal feel is a wide a$$ed best guess.


Ahh you are correct. I'm comparing the VW parts referenced to that of the car, not the Jeep. Yes it gets confusing.

The data on the VW:



Caliper Piston
Steel & Aluminum Caliper Pistons
6 Piston Front Caliper; 330mm Front Disc
[34mm]
Front
146.34015
34mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
6 Piston Front Caliper; 330mm Front Disc
[36mm]
Front
146.36021
36mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
6 Piston Front Caliper; 330mm Front Disc
[38mm]
Front
146.38053
38mm Piston
4




53285

4.7sq" and fit with 27mm. Low line pressure, high clamp pressure.


And the data on the Cayanne:




Caliper Piston
Steel & Aluminum Caliper Pistons
330mm Front Disc
[34mm]
Front
146.34015
34mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
330mm Front Disc
[36mm]
Front
146.36021
36mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
330mm Front Disc
[38mm]
Front
146.38053
38mm Piston
4








Caliper Piston
Steel & Aluminum Caliper Pistons
350mm Front Disc
[30mm]
Front
146.30017
30mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
350mm Front Disc
[34mm]
Front
146.34015
34mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
350mm Front Disc
[38mm]
Front
146.38053
38mm Piston
4






The larger 350mm disc having 4.22sq" of piston. That paired with the larger disc to keep bias in check. And a slightly smaller bore mc

53286

Higher line pressure and lower clamp pressure.


The SRT8 CAR:




Caliper Piston
Steel & Aluminum Caliper Pistons
SRT8, 6.4L Hemi
Red
Front
146.44010
44mm Piston
4






53287

Total area 4.7sq" and back again to a lower line pressure paired with higher clamping pressure.


I think I've found your six pot Jeep Brembo:



Caliper Piston
Steel & Aluminum Caliper Pistons
SRT8; 380mm Front Disc

Front
146.40029
40mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
SRT8; 380mm Front Disc
[28mm]
Rear
146.28002
28mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
SRT8; 380mm Front Disc
[32mm]
Rear
146.32009
32mm Piston
4






Total area: 4.13sq" which is surprisingly smaller than I'd have expected.

Paired with a 27mm stock MC.
*won't let me load the image

That would mean a low line pressure combined with a lower clamping pressure. To make that work effectively and keep brake balance in check you'd need a yet larger rotor. Oh look; we have one! A 380mm disc. The basics of this remain the same science: a larger disc usually uses a lower pressure application design. There's no need to clamp the crap out of it when you can use the leverage of the disc. *Not granted as was pointed out there could be variations in pedal lengths here also. But....I doubt it. The same pedals would be installed across the board on the Jeep, only they hydraulic formula changed. And while such things could be changed it would NOT change the hydraulics in the brakes- it would only effect the human leg effort needed to push the pedal. In the Jeep study above the leg effort would be up a bit I suspect just looking at the relationship. That's driver feel or feedback, not brake torque.



All that factual info aside...I'm glad you're able to go out and get hard parts and measure them. Lucky for you I don't have to do that as I'm 'in the business' and have access to such info without shelling out all that money. And lucky for you that despite you continued 'case of the ass' attitude I'm more than willing to help and share this info with others. I'll dig a bit deeper to help (you) others get the info if I can.

A larger bore will not move as far, a smaller bore mc farther. Both however are simply relative to the total requirement of the caliper. Knowing the area of each caliper is the only way to compare changes to what you have now. That 'arm length' you're trying to reference is called the pedal, or more rightly the pedal ratio. There are actually two arms. And changing one or both of those will change feel- you're right.

But I'm assuming you have no intentions of changing your pedal- either the short or long arm, or ratio in your vehicle. That being the case comparing the piston area and mc bore ratios is of extreme importance. Anyone trying to compare data correctly has to have a clear image of where they start and then cause and effect of change. Given you're NOT changing pedal or ratios it more fact than a guess.



I'm ok if he wants to banter it...hell, I'm even ok being proven wrong. So far he's the only one tossing out ideas more than data. Put up the facts and let the results fall where they may. All I'm doing is referencing known info in trying to help others with that cause and effect. And last time I checked I have a couple more year of doing, right or wrong, than he does. So it goes.

Todd TCE
02-11-2014, 03:33 PM
Anyhow....moving on to knownman's question of rotors:

The reason I asked about the disc was that it's often taken that a "better" or "high performance" disc somehow brakes better. That's not exactly the case. It's like brake fluid: there's something better about it but we can't quite put our finger on it alwys so we assume/are sold on the notion that is must make me stop quicker. (like how many piston you have vs area which we covered a few pages ago)

Rotors are built to be a heat sink. That's about it really. How they do that is by absorbing and dissipating heat. The build of that rotor: it's total thickness, air gap, iron quality, and vane structure all play a roll in the end product. What doesn't change however is it's working dimension.

Taking on 14" brand rotor vs another is not going to shave 20ft off a stopping distance. Because rotor or brake torque is calculated based on the diameter (radius etc) the same size disc creates the same net result. Be it $300ea or $75ea it's not going to add more torque.

Where the 'better' disc shines is often its ability to work in a high stress duty cycle over and over. Much can be said of the BBK: it won't really stop you any sooner in the most basic of stops. (like stopping on ice; the distance is relative to the tires Cf to the road, not a massive rotor with many pistons) When you put a heavy car into hard use you build up heat. That heat has to be managed effectively and quick. Or it over heats. The better discs do a more efficient job of cycling that heat.

So what I was driving at is this: A rotor is a rotor is a rotor...until it's not. If you're buying 1pc or 2pc discs with the expectation of shorter stopping distances it won't happen for the most of daily use. The key will become pad. The pad is what creates the friction. More friction means a more rapid deceleration of the rotor. That force is then only limited by the ability of the tire to adhere the demand to the road.

bobsmyuncle
02-11-2014, 03:37 PM
And no I'm not telling you what the actual numbers are.. buy your own calipers and master cylinders and do your own real reseach.


Really? That is what this entire site is all about. How much information have you gleaned from the pioneers of the LX platform because they were willing to share.

From your post count you'd think you'd be a bit more aware of the way things work here.

As for the rest of us, let's just ignore the childish behaviour and continue the discussion.

knownman
02-11-2014, 03:44 PM
Todd,

In response to your question.

I would refer to upgraded, admittedly with limited knowledge on the subject, as a larger diameter rotor and the necessary brackets which would allow the OEM caliper to work with it. In my mind this would allow the mechanical advantage of moving the clamping force further out on the rotor. Now if that isn't worth the investment or is not commercially available I would just ask for a recommended pad replacement which has better bite. (read lack of technical vocabulary) A pad which would live on the street and maybe not dust as much as the stock pads do.

I'm most likely not in the market for too expensive of an option hence I wish to keep the calipers the car came with. Just would like to get some extra stopping power if it's available.

Thanks,

posted after yours.

whats a good compound? I'm not worried about short pad life as long as it's not insanely short. 10K is okey dokey

Matt:thumbs_u:

Todd TCE
02-11-2014, 04:06 PM
Todd,

In response to your question.

I would refer to upgraded, admittedly with limited knowledge on the subject, as a larger diameter rotor and the necessary brackets which would allow the OEM caliper to work with it. In my mind this would allow the mechanical advantage of moving the clamping force further out on the rotor. Now if that isn't worth the investment or is not commercially available I would just ask for a recommended pad replacement which has better bite. (read lack of technical vocabulary) A pad which would live on the street and maybe not dust as much as the stock pads do.

I'm most likely not in the market for too expensive of an option hence I wish to keep the calipers the car came with. Just would like to get some extra stopping power if it's available.

Thanks,

posted after yours.

whats a good compound? I'm not worried about short pad life as long as it's not insanely short. 10K is okey dokey

Matt:thumbs_u:



You have a pretty good grasp of this Matt. Yes you are correct: the large disc give more total torque. Relative to the clamping.

Lets say you push with 50lbs of effort on your pedal. Going up 1" in rotor diameter increases the total torque. The trick however is that moving from say 13" to 16" seems like a great idea doesn't it? But that shift also effects the overall balance or bias of the car. In a car of say 65/35 bias your change could go to 80/20. That means that the front tires are doing 80% of the work. This in turn is often the bad effect poorly designed kits have; they over tax the fronts and let the rears just follow. Problem is that can actually decrease brake effectiveness.

Look over the stats (the ones I just toss out) and you'll see a pattern: when the disc gets larger- the piston area gets smaller. That's bias checking.

To do thing 'right' you'll need a snap shot of what you have and compare cause and effect of change. Then evaluate if it's a better choice really. Some prefer to just bolt things on and guess it must work, others use a bit more involved process of evaluation. Both can end up with the same working results, I prefer to know not just 'how' but 'why' it does or doesn't work.

When you move from your existing brakes your goal should be to stop as well or better than you do now. Larger disc generate more torque, can lower operating temps, lower pad wear (just as you wanted there, but relative to how you drive, slotted or drilled, and total pad material available) and simply make more efficient torque.

I don't know what you have now so I can't take a stab at the options tho!


BTW: I don't sell any of the stuff being talked about above so I don't really have a horse in that race. I'm just putting up the info so others can use it. I don't think I've even made one reference to selling something until you asked here.

Quick
02-11-2014, 04:08 PM
So just to wrap that up. We're talking about brakes and braking power. Once you get to the calipers the only input is line pressure (and maybe volume? but I don't think brake line diameters vary significantly or that the volume difference/cylinder area is that much different that one master cylinder would have a problem and another not?).

So it's areas and line pressure in the context of the caliper right? I don't see where the master cylinder and pedal feel/travel are much of a functional consideration are they?

Hemissary
02-11-2014, 05:07 PM
If pedal points (lengths of arms) remains the same, the smaller the piston area, the further the piston has to travel within it's master cylinder bore to achieve a given line pressure. Add to this the pedal feel becomes less sensitive to road anomalies making it easier to over or under-apply.

With a larger diameter piston, more pedal (foot) pressure is required and it travels a lesser distance achieve the same line pressure. But feedback through the brake pedal is better for sensing when you are at the limits of tire adhesion.

knownman
02-11-2014, 05:10 PM
I'm rolling on '09 SRT8 Challenger Brembos with stock 20" Alcoas, read decent rolling weight 27.5lbs each plus tires. Still have the 255 F1 GoodYears which were rears on the front but use 295 40's in the rear made by Falken to get this thing going.
Car has a push at high speed entry but that's another thing I need to iron out with my suspension tuning. Rear bite increased with the Falkens and I can still oversteer on demand with the loud pedal but I'm too old to be playing like that on the street. I've got some tuning to do and possible swapping out the front spoiler for the 2011 plus to add some downforce.

All in all just looking to make sure I address the binders with at least a compound upgrade if it's available. Some have said the stock pads are actually good and maybe the only real issue is the heavy dusting they create after very few miles. I have 10K on the car and the pads will be due for a change. Just want to know what I should be looking for.

Hemissary
02-11-2014, 05:10 PM
Todd, do you know if there are different master cylinders (different piston diameters) between the early (05' - 08') RT and SRT platforms?

Todd TCE
02-11-2014, 05:21 PM
If pedal points (lengths of arms) remains the same, the smaller the piston area, the further the piston has to travel within it's master cylinder bore to achieve a given line pressure. Add to this the pedal feel becomes less sensitive to road anomalies making it easier to over or under-apply.

With a larger diameter piston, more pedal (foot) pressure is required and it travels a lesser distance achieve the same line pressure. But feedback through the brake pedal is better for sensing when you are at the limits of tire adhesion.


Very well stated.

Now...conversely of that: the opposite is true of piston area in the caliper itself. Just think about; it's working the other way.

Put on a caliper with too much CALIPER piston area you have to displace more fluid, pedal feel is soft. Clamp force is up. You don't push as hard.

Put on a caliper with too little CALIPER piston area you don't displace as much fluid, pedal is rock hard. Clamping is less. You push harder.


Manufactures balance the systems based on these relationships. But also on bias relative to each end of the car to make it all work as one.

Quick
02-11-2014, 05:23 PM
If pedal points (lengths of arms) remains the same, the smaller the piston area, the further the piston has to travel within it's master cylinder bore to achieve a given line pressure. Add to this the pedal feel becomes less sensitive to road anomalies making it easier to over or under-apply.

With a larger diameter piston, more pedal (foot) pressure is required and it travels a lesser distance achieve the same line pressure. But feedback through the brake pedal is better for sensing when you are at the limits of tire adhesion.

Sure, but up to now the thread has been "what will it take to stop more effectively" (and mostly in a road racing context). I see that as all being in the wheel wells -- calipers, pistons, pads, rotors, cooling, etc. I see the master cylinder, pedal arm, feel, etc. as "details". Once you're set in the wheel wells then the rest of the stuff is relatively minor bits to match your solution and personal preference.

Todd TCE
02-11-2014, 05:32 PM
So just to wrap that up. We're talking about brakes and braking power. Once you get to the calipers the only input is line pressure (and maybe volume? but I don't think brake line diameters vary significantly or that the volume difference/cylinder area is that much different that one master cylinder would have a problem and another not?).

So it's areas and line pressure in the context of the caliper right? I don't see where the master cylinder and pedal feel/travel are much of a functional consideration are they?


Pretty much.

The only significant input once you get to the caliper is how much pressure there is and how much total piston area you have that the pressure is pushing.

Taking that same final value and varying it on a disc diameter effects how much torque you get. There are variables such as the pad Cf and Effective radius to consider but for same-same issue this is all you'd need to start.

No MC bore size is not relative to the overall pressure just to compare calipers. BUT...if you were to make a huge change in caliper piston area you'd need to know that and evaluate the bore of the mc to pair with it. You can have a small bore(S) system at high pressure or a large bore(S) system at low pressure. Same result. Where goes to hell is mixing and matching without grasping cause and effect.

For much that reason I put up the two bias calculators I have. One is quite simple for cause and effect, the other far more involved for dual mc design.

And as was pointed out: just because you can make more pressure, larger leverage or more total torque you still can't always put it to the ground! So what if it makes 1.5X the torque at a given input? If the wheel locked up 1.1 then the other .4 increase is of no value. Think about that ice situation again. The dry is the same, just more grip to the limit.

Todd TCE
02-11-2014, 05:43 PM
I'm rolling on '09 SRT8 Challenger Brembos with stock 20" Alcoas, read decent rolling weight 27.5lbs each plus tires. Still have the 255 F1 GoodYears which were rears on the front but use 295 40's in the rear made by Falken to get this thing going.
Car has a push at high speed entry but that's another thing I need to iron out with my suspension tuning. Rear bite increased with the Falkens and I can still oversteer on demand with the loud pedal but I'm too old to be playing like that on the street. I've got some tuning to do and possible swapping out the front spoiler for the 2011 plus to add some downforce.

All in all just looking to make sure I address the binders with at least a compound upgrade if it's available. Some have said the stock pads are actually good and maybe the only real issue is the heavy dusting they create after very few miles. I have 10K on the car and the pads will be due for a change. Just want to know what I should be looking for.


There's nothing wrong with the function of these parts really. I don't care for the mickeymouse front calipers and others complain of the rusty piston etc but they work quite well. Dust is a by product of friction. How much you can stand may vary by how well you want to stop. A low Cf pad won't work so well, so you'll push harder and not stop as well perhaps, but the wheels are clean.

If I were to push you to run a W6A front caliper kit on there that's one idea. But the problem is you have 44mm bores. Or 4.7sq" of piston area. The larger bore model has 5.3" making the pedal a bit softer but more clamping force. The smaller bore has 4.1" making you push harder as it clamps less. I'd have to weigh the options of each.

Truly neither one of these is the ideal animal. I'd do the W4A with 1.62/1.88 bores or 4.8" of area. See: four can be better than six! Moving to the 5.3 would work but could mean less rear brake. Going down in size shifts the bias to the rear but you'll hit the knee point of the prop valve sooner. Nothing comes for free here. Going down in size AND putting the smaller RT mc on the car would be a pretty good plan.

Because I don't do stock pads I'm of no help in that realm. Try some of the other vendors and ask these guys what they like.

Todd TCE
02-11-2014, 05:46 PM
Todd, do you know if there are different master cylinders (different piston diameters) between the early (05' - 08') RT and SRT platforms?


Yessir. I didn't pull it up right now but there were 1.0 and 1.063 bores.

For RT owners who bought kits from me (or the Wilwood (copy)) kit you got the right stuff. Buying from others tho folks got the bigger bore calipers and at times complained of pedal feel. The only fix for that was to go to the larger bore mc off the SRT car.

There's a cut off year some place I saw on the new Challenger. Don't recall what or where. I'll try to look later.

Dan79
02-11-2014, 07:45 PM
(That changes all your calculations which BTW you assume...... and I'm actually measuring.... and your numbers are wrong.) And no I'm not telling you what the actual numbers are.. buy your own calipers and master cylinders and do your own real reseach.


WTH lol. Wow...

Blown7
02-12-2014, 05:10 AM
WTH lol. Wow...

Told ya.... I was done talking and arguing..and didn't use crap Wilwood

http://i25.photobucket.com/albums/c96/Blown7/BrakeBremboupgrade090.jpg (http://s25.photobucket.com/user/Blown7/media/BrakeBremboupgrade090.jpg.html)

Todd TCE
02-12-2014, 10:10 AM
I thought you were going away? Again. Or again.



Digging up deeper info on the Cayenne (think I have it spelled right now) I see they offered a full ceramic set up at 410mm. A full 16" plus~! Guess I don't spend enough time in the Porsche dealer....

That kit comes with a six pot with non differential bore design. A bit surprised at that. All bores are 36mm for a total take of 4.75". And there's only one mc bore spec for the entire vehicle offering.

I have no experience with ceramic discs but I'm seeing two things that have me thinking.

First the square bore spec makes me wonder if pad taper is less of an issue with this type of set up?

Secondly I see the area is the same as some of the others. From reading info by Corvette owners they all seem to say the ceramic discs don't work well when cold. That would have me thinking that perhaps the engineers have added a boost to the clamping to make up for the loss of bite when cold. They say the Vette works well when heated up so a small change from say 4.75 down to 4.5ish wouldn't be huge for feel. But just might make up for the lack of cold bite. Anyone here have a ceramic set up?

Todd TCE
02-12-2014, 04:28 PM
Came across some more MB AMG stuff you might be interested in looking at.


SLK55 AMG 30/34/38mm
53299


SL63 AMG 34/36/38
53300
Available in red even.

Rose City GC SRT8
02-13-2014, 11:02 AM
The SRT8 CAR:




Caliper Piston
Steel & Aluminum Caliper Pistons
SRT8, 6.4L Hemi
Red
Front
146.44010
44mm Piston
4






53287

Total area 4.7sq" and back again to a lower line pressure paired with higher clamping pressure.


I think I've found your six pot Jeep Brembo:



Caliper Piston
Steel & Aluminum Caliper Pistons
SRT8; 380mm Front Disc

Front
146.40029
40mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
SRT8; 380mm Front Disc
[28mm]
Rear
146.28002
28mm Piston
4



Caliper Piston
Steel & Aluminum Caliper Pistons
SRT8; 380mm Front Disc
[32mm]
Rear
146.32009
32mm Piston
4






Total area: 4.13sq" which is surprisingly smaller than I'd have expected.

Paired with a 27mm stock MC.
*won't let me load the image

That would mean a low line pressure combined with a lower clamping pressure. To make that work effectively and keep brake balance in check you'd need a yet larger rotor. Oh look; we have one! A 380mm disc. The basics of this remain the same science: a larger disc usually uses a lower pressure application design. There's no need to clamp the crap out of it when you can use the leverage of the disc. *Not granted as was pointed out there could be variations in pedal lengths here also. But....I doubt it. The same pedals would be installed across the board on the Jeep, only they hydraulic formula changed. And while such things could be changed it would NOT change the hydraulics in the brakes- it would only effect the human leg effort needed to push the pedal. In the Jeep study above the leg effort would be up a bit I suspect just looking at the relationship. That's driver feel or feedback, not brake torque.




Great info, Todd.

Correct me if I am not reading this correctly:

If you were able to adapt the larger 380mm WK2 rotor and WK2 6-piston Brembo to the WK SRT8, then would a WK2 master cylinder (or equivalent) that delivers low line pressure/clamping pressure yield a pedal feel that is closer to what the SRT engineers have designed for the rig?

Todd TCE
02-13-2014, 11:16 AM
Great info, Todd.

Correct me if I am not reading this correctly:

If you were able to adapt the larger 380mm WK2 rotor and WK2 6-piston Brembo to the WK SRT8, then would a WK2 master cylinder (or equivalent) that delivers low line pressure/clamping pressure yield a pedal feel that is closer to what the SRT engineers have designed for the rig?


Forgive me...my head spins on some of this as I don't really "speak jeep" well. But! I think I might be able to make this pretty simple.

Anytime you enlarge the mc bore or decrease the piston area: the pedal will feel 'harder' and you will need to push harder to generate the end clamp force.

Anytime you decrease the mc bore or increase the piston area: the pedal will feel 'mushy' and you won't need to push as hard go generate the end clamp force.



IF you put a larger disc on the vehicle AND you decrease the piston area all is not lost tho. There is an added value to that larger disc- more leverage- that may be enough to offset the loss of clamping force (for the same given leg effort, without a need to push harder) to achieve the same final rotor torque.

I certainly can't speak for the designers but the more tactical drivers tend to like a firmer pedal. If that transfers over to the design team that's good. But most engineering for cars tends to lean towards the more all-around softer feel.


Some of this transfers over to another platform: SHO. Complaints of poor braking and feel were common. Ford finally answered with some changes; a different pad but also a larger bore mc. Buyers jumped up and down about how much better the car stops now with it's better brakes. Ahh...as some have figured out; not really, you just like the feel better and have to push harder. All of which is a good thing mind you. But a lot of it's in your head.

done
02-13-2014, 03:04 PM
All of this reminds of my auto sales days (many years ago) selling Renaults. They had disk brakes and not many people had ever driven a car with disks. So, I demonstrated the brakes on a test drive. Never locked up the wheels and didn't really stop that hard...... but no one had ever demoed brakes to them before, so the prospects were always impressed.

The point being that a new brake job/change always feels better because you are now paying attention to the brakes and stopping more aggressively to "test" the brakes.

GODZILLA88
03-31-2014, 07:44 AM
So has anyone completed this and have any respectable data? Braking distance vs stock? I think that's what it will come down to in the end; theory is always one thing, proving it is another. I think a majority (probably around 90%) interested are in it for the looks of the massive calipers, like myself. I don't road race, not sure if I ever plan to. Will cross that bridge once I get there. I WILL have these on my car within the next few months and will have real data, all the parts (with prices) needed, pics of install, maybe do a DIY write up.

MattRobertson
03-31-2014, 01:39 PM
Data is king. Especially given the discussion above as to benefit. If you write it up with pics, comparative stopping distances that'd be a shoo-in for the Knowledge Base, I would think. And one heck of a well-discussed thread.

GODZILLA88
04-01-2014, 12:00 AM
Calipers bought, off to Mike for powder coat. Hang tight for data. I'll be contacting Todd about rotors. Going with a one piece design. Stainless lines arrived last week from StopTech, can't wait to get my hands on these calipers.

S. Artee
07-10-2014, 03:14 PM
Any updates on this?

For matters of fundamental comparison, I completed a similar conversion on my SRT-6. Went with the SLK55 AMG p03 performance brake package (6 piston front, 4 piston rear).

I can attest to every theoretical posted by Todd. I've seen a greater ability to abuse the pedal and keep the same stopping power, and also picked up better braking feel. I've not had a chance to test the stopping distance versus what the automags claim, but I would think it's no lengthier in any case. -I concede that any benefits (repeated hard stops aside) are likely due to the pads, where the feel and endurance where benefited by the remaining hardware.

For those interested... http://www.crossfireforum.org/forum/tsbs-how-articles/64983-yet-another-amg-brake-upgrade-how.html