Here's the skinny on the Why of brake squeal and the How to stop it. I was planning to append this to my thread on swapping brake pads, but it's come up enough lately that I think it'll be more helpful on its own.
For the purposes of this discussion, I'm talking about the intermittent squeal you get at less than full pedal pressure - NOT a constant squeal all the time, regardless of pedal pressure - that one likely means your pads are worn down to the limits and need to be replaced. There are also other conditions with faulty/worn parts that can cause it, but here I'm talking about the normal squeal that you'll encounter even if your parts are perfect.
A little groundwork: The brake pads are pressed to the rotors either by:
- Pistons on both pads (in the case of Brembos and Wilwoods, etc.) or by
- Piston(s) on one pad, against the floating caliper itself on the other side (in the case of stock brakes).
Either way, force is applied to each pad from something behind it.
Here's the matter at hand:
The squeal you hear is a result of vibration between the brake pad and rotor that occurs when less than full clamping force is applied to the pads. It's also called "chatter" or "rattle," but it's a squeal that you hear. That micro-vibration is eliminated by firmer pedal pressure (clamping force), but there are ways to eliminate it at lower pedal pressure as well.
To stop that micro-vibration, you need to dampen the contact patch between the back of the pad, and whatever acts upon it (piston or caliper).
In these two photos, you can see the wear marks on the back of each pad, and see where the contact patch is:
There are a few substances available to do the dampening:
This is what I was sold when I went in and asked for "anti-squeal":
Essentially the same as this (but NOT the same as chassis grease - you need a good Moly-based High-heat grease):
The best thing I've found is this - it's much tackier than grease, and lasts longer:
Before you apply whatever you decide to use, clean off all the contact surfaces well - the backs of the pads, and the face of the pistons/calipers:
Then spray (or smear) the stuff onto the contact patch:
And reassemble the caliper assembly:
This stuff is messy, and it will collect dirt. I suppose if you wanted to, you could take some brake cleaner or lacquer thinner to the exposed parts after it's reassembled. Probably not a bad idea.
Go for a drive around the block right away, and let everything seat where it wants to.
OK, one other thing you can do. These are called the anti-rattle clips, and their purpose is to apply some tension to the pads to keep them from vibrating:
You can tweak them a little bit so they apply more tension to the pads like so:
And here you can see the slight bend where the clip will contact the pad:
In most cases, the application of something to the contact patch will solve the majority of squealing issues. In my experience, grease did it temporarily. The tacky adhesiveness of the aerosol stuff seems to work a lot longer.
Also, here's Dave Zeckhausen's tutorial on how to properly bed in your brakes, which you should do: http://www.zeckhausen.com/bedding_in_brakes.htm
Hope it helps! Cheers.
Last edited by Junior; 11-14-2008 at 11:13 PM.
thats the same reason i had front end noises, thought it was tension struts, had those replaced, thought it was tie rod ends, had a new rack installed..then went to do the brakes one day, realized that same tacky stuff on the pads wore off, so i cleaned them up, re-installed everything, with out the tacky grease, the front end noise was 10x worse, rattling and clanking like crazy, pull the front wheels back off, applied crc brake quiet to the pads , put everything back together, let it set and cure for bout a half hour, went for a drive, solid as a rock, no more front end noise/rattling..
Thank You Haz
Great stuff! I've found that in a lot of cases, the nightmare problems often have a simple fix - it's just a matter of narrowing down the scenario.
Electrical work is that way - often it's a loose wirenut somewhere - it's just a matter of sorting out where in the system that particular wirenut happens to be...
Glad to hear yours was an easy fix - too bad you had to do all the other stuff before finding it!
u mean too bad the dealer did all that stuff under waranty, and didnt realize it was just loose/rattling brake pads..
even took the tech for a ride adn he said it himself, yup there definately som clanging going on up front, i think its the tie rod ends...a week later, i still heard it, brought it back and i mentioned tension struts, like i read here, dealership replaced both of those, noise still tere, thats when i took te wheels of and noticed the pads are held to the caliper via that brake quiet..with out it, or once it starts breaking down, the pads have a lot of play in them...
Great write up Mike. I have the yellows too and the rears are such a nightmare I had to take them off. I guess it's time to try again. Thanks.
(Waiting "patiently" for the 300C SRT8 8-speed) Coming.....soon?
Thanks for the info... always wondered why auto zone etc. always wanted to sell you some of that stuff, but really didn't know where to apply it. I do now!
this is so perfect,as recently i have been getting that squeak at light brake pressure. Saying to myself that i would be removing the wheels and taking a look at the breaks,so this is some great info at the perfect time..Thanks alot junior and beans to you.........
06 SXT AWD Magnum, Silver Steele Metallic: Chrysler's Red headed stepchild!!!
I drive mine like I just left the bank after an unapproved forced permanent loan ...
Great post Mike - thanks. Mine have started squeaking intermittently again, especially after washing the car.
2006 Magnum SRT8 "HEMIWAGN"; OST Dyno tuned; Frank Racing Extreme Heads, Scudd Cam & Ported Intake; Paramount Performance Dominator 3600TC & Valvebody. Best 1/4: 10.815@ 124.26 MPH, 1.497 60', 3400lbs with driver, DA +1300
Bump, to make it easier for me to find.
great post. Thanks for the detail.
I just want to make sure some noob doesn't decide to put grease on the back of all his pads. Once they heat up it can run, drip, and even catch fire! Does funny things to the coefficient of friction, too!!!!
The CRC is great stuff. Note that proper bedding also solves 90% of these complaints.
06 300C SRT8
Best ET-12.794, trap 110.9 All stock in negative D/A
great thread. Thanks Junior.
The Old: Stock 5.7 Bottom End | Lead Foot | 11.861 @ 112.76 1.63 60'
The New: Forged Arrington 6.1 | MMPG Top End | Paramount Drivetrain | 11.67
I thought the squealing would subside once all the coating from the rotor and pads wore off but that is not the case, it's still squealing at anything other then full pressure. I hate to have a beautifully clean and nice looking 300 and then pull up squealing like a pig to a stop.
They're not looking at me because of the clean car, or the nice mods, or the bumping stereo system - They're looking at my from the high pitch squeal from the brakes. LOLOLOLOLOL!!!!!!!!!!!!!!!
I'm gonna apply some of this stuff this weekend.
"Death Smiles at Everyone -- Marines Smile Back"
MOD LIST: C/F Hammer, Flowmaster Ex, FRI-Sidewinder Cam, Gibson Headers, Predator, B.T. Ported T.B., Lil Silver Box, Red Illum Rear Wing, SRT Interior, 09 Eagle Intake Mani, CTP Spacers, SRT Rails & Injectors, SRT Rear w/3.55 Gears and 2010 R/T Axles, Brembo Brakes, Layin Low Bagged with a Magnum SRT Front Swap....What's Next?