AWD Staggered Wheels, Offset?

[nyxis]

Just wondering if anyone is running staggered wheels like a 20x8.5 front and a 20x10 rear on the AWD. How about 22s? .. If you are what backspacing do you have? .. Pictures would be nice too..

[Scott]

Just wondering if anyone is running staggered wheels like a 20x8.5 front and a 20x10 rear on the AWD. How about 22s? .. If you are what backspacing do you have? .. Pictures would be nice too..

The owner’s manual, page 235, has a strong cautionary statement that unequal tire size may cause failure of the front differential and/or the transfer case.

Obviously, this warning refers to tire circumference and not width. But, if you are not using four of the same tires there will be some difference circumference. Even replacing worn tires of the same model/size, 1 or 2 at a time instead of all four results in a few revolutions per mile difference. In a two wheel drive car with an open differential, this is easily handled. But it not clear where the slippage occurs and where forces are directed with AWD.

I have been trying to find out how close the circumference between tires needs to be, but don't have a definitive answer yet. Stay tuned.

A related thread: http://www.lxforums.com/board/showthread.php?t=20082
I'm gathering some thoughts and will post more info there.

Scott

[VanillaRT4me]

The owner’s manual, page 235, has a strong cautionary statement that unequal tire size may cause failure of the front differential and/or the transfer case.

Obviously, this warning refers to tire circumference and not width. But, if you are not using four of the same tires there will be some difference circumference. Even replacing worn tires of the same model/size, 1 or 2 at a time instead of all four results in a few revolutions per mile difference. In a two wheel drive car with an open differential, this is easily handled. But it not clear where the slippage occurs and where forces are directed with AWD.

I have been trying to find out how close the circumference between tires needs to be, but don't have a definitive answer yet. Stay tuned.

A related thread: http://www.lxforums.com/board/showthread.php?t=20082
I'm gathering some thoughts and will post more info there.

Scott

Scott,
For staggered sized tire/wheel combinations in the 22" diameter size, there are some that work such as:

Dunlop SP Sport Max - 265/35-22 and 305/30-22, both exactly 29.3" diameter

Continental CrossContact UHP - 265/35-22 and 315/30-22, with diameters of 29.3" for the 265 width front tire and 29.4" for the 315 width rear tire

Pirelli Scorpion Zero Asimmetrico - 265/35-22 and 295/30-22 with diameters of 29.4" for the 265 width front tire and 29.3" diameter for the 295 width rear tire.

For 20" wheel fitments, a 255/45-20 for the front and a 275/40-20 are the same diameter as well.

I believe that AWD will allow for a .1" diameter difference in tire size.

[desmo_dude]

For 20" wheel fitments, a 255/45-20 for the front and a 275/40-20 are the same diameter as well.
I think you mean 285/40-20 for the rear. This is the setup coming from the factory in the Grand Cherokee SRT8.

http://www.goodyear.com/media/pr/23074ti.html

http://www.car.ee/wallpapers/previews/jeep-grand-cherokee-srt8-275.jpg

If Foose made the Nitrous 20x10 with a 50-55mm offset I would've staggered them, but it wasn't to be... Also, no one seems to be able to find a 285/40-20, let alone in the not yet released Goodyear RS-A run-flats (which I'm sure will suck) anyway, so staggering 20's safely in an AWD is definitely a challenge. I gave up. As for 22's, I couldn't afford to keep decent tires on them... I couldn't justify having to settle for entry-level 22" tires for the same price I could get Scorpion Zeros in 20".

[VanillaRT4me]

I think you mean 285/40-20 for the rear. This is the setup coming from the factory in the Grand Cherokee SRT8.

http://www.goodyear.com/media/pr/23074ti.html

http://www.car.ee/wallpapers/previews/jeep-grand-cherokee-srt8-275.jpg

If Foose made the Nitrous 20x10 with a 50-55mm offset I would've staggered them, but it wasn't to be... Also, no one seems to be able to find a 285/40-20, let alone in the not yet released Goodyear RS-A run-flats (which I'm sure will suck) anyway, so staggering 20's safely in an AWD is definitely a challenge. I gave up. As for 22's, I couldn't afford to keep decent tires on them... I couldn't justify having to settle for entry-level 22" tires for the same price I could get Scorpion Zeros in 20".

Your points are well taken, Desmo_Dude.

If a person was willing to pay big bucks for some forged wheels, a staggered 20" or 22" set could be made-to-order from HRE, Fiske, Asanti, iForged or one of the other custom wheel manufacturers. They could meet those exact offset specifications (50-55mm) that an AWD would require.

[nyxis]

Your points are well taken, Desmo_Dude.

If a person was willing to pay big bucks for some forged wheels, a staggered 20" or 22" set could be made-to-order from HRE, Fiske, Asanti, iForged or one of the other custom wheel manufacturers. They could meet those exact offset specifications (50-55mm) that an AWD would require.

so with staggered front and rear wheels, both would be 50-55mm offset? ..

or are we trying to keep the backspacing close to 3.5"

so for a 10" wide wheel we would be 50-55mm and a 8.5" wheel we would be 30-35mm?

[Scott]

Scott,
I believe that AWD will allow for a .1" diameter difference in tire size.

A former tire shop owner used a rule of thumb of 1/4 inch circumference, very close to your spec; you guys may well be right. As you may have noticed from my other posts, I’m a bit wobbly about even this little difference for long term use. It amounts to a front to rear difference of 2 revs per mile at the tires, and (x3 for axle ratio) 6 revs per mile at the transfer case. I am trying to find something definitive that indicates whatever is slipping is designed to accommodate this on a continuous basis.


Nice of you to list tires matching in size. Prudence suggests actually measuring the tires before installation to make sure they are as close in size as the specs indicate. Rounding or other errors exist in tire mfg specs and could be important with an AWD.



Scott

[done]

so with staggered front and rear wheels, both would be 50-55mm offset? ..

or are we trying to keep the backspacing close to 3.5"

so for a 10" wide wheel we would be 50-55mm and a 8.5" wheel we would be 30-35mm?

Ideally you would want to retain the offset at 55mm on both front and back. However, the front gets a little tight as you increase the rim width. You only have about 1/2 inch clearance on the backside of the stock wheel. So with the same offset, you could maybe run an 8" rim. If you decreased the offset to 42mm, then the 8.5 or 9" rim would work on the front.

I don't know about the back wheel, I have never measured there, but I would supect a 10" with the 42mm offset would be fine.

[Scott]

Hey Desmo_dude,

The "Desmo" in your handle, did you pick that up from the name of the Ducati valve train? I used to motorcycle quite a bit and that caught my eye. :)

Scott

[desmo_dude]

You got it! I own a '97 Ducati 916. Desmo_dude is my name over at http://www.sportbikes.com (http://www.sportbikes.com/)
I guess it kinda stuck, cuz I use it everywhere (forum handles, gamertags...)

I don't have a cool avatar here yet, but here's the one I use at sportbikes.com... :)

http://www.916rider.com/916_rotate.gif

[Scott]

Great bike. I used to roadrace motorcycles and hence appreciate the Ducati handling advantage, although, never owned one myself. I find myself rooting for them when I see racing on TV.

I can't make mention of a big Ducati without marveling about its glorious exhaust note. Above idle, it is similar to and just as "bad" sounding as any high-perf V-8. My wife heard one drive by and she thought it was a hot rod car.

Congrats on your new AWD. I read your AWD/RWD comparsion in another thread with interest. I also had opportunity to make this comparison and had about an hour and half in each car. If you like how the AWD handles in the dry, wait until you see what it does on wet roads. With the power distributed over more wheels, one can make great use of the hemi power without sliding or being held back by ESP. AWD literally extends high-perf driving to slippery surfaces! If your car came with the Continentals, they are predictable in the wet, but mediocre in the snow. Braking distance in the white stuff isn't the best. Tip: Keep 40 psi in those conti's for any fast driving, otherwise they roll over on to the side walls. Welcome to the forum.

Scott

[desmo_dude]

Thanks for the tips....

And yeah, it's getting harder and harder to root for the Ducatis these days though, what with all the power the inline-4's are making, our poor V-twins are getting their a$$es handed to them. Next season should be decent for Ducati in the AMA, with two World Superbike champs right here in America (Hodgson and Bayliss).

[VanillaRT4me]

Thanks for the tips....

And yeah, it's getting harder and harder to root for the Ducatis these days though, what with all the power the inline-4's are making, our poor V-twins are getting their a$$es handed to them. Next season should be decent for Ducati in the AMA, with two World Superbike champs right here in America (Hodgson and Bayliss).

Doesn't the V-twim Ducati still have the advantage coming out of the turn with its tremendous torque. I thought this was an advantage the inline-4's could never match.

I'm still a lifelong Ducati fan even though I now ride a Harley. I miss the Monster!

[desmo_dude]

Doesn't the V-twim Ducati still have the advantage coming out of the turn with its tremendous torque. I thought this was an advantage the inline-4's could never match.
That used to be true, not only because of the flat, predictable torque curve of the twins, but the power pulses to the rear tire are a lot more forgiving, allowing the twins to get on the throttle sooner... But tire technology's improved so much that even a brutal IL4 can get on the gas as early as the twins and the tire will still live to the end of the race. The liter twins don't stand a chance against the inline-4 liter bikes in the straights. So unless the rules change allowing larger displacement twins, their days are numbered.


I'm still a lifelong Ducati fan even though I now ride a Harley. I miss the Monster!
Yup, there's truly nothing (on 2 wheels or 4) like the roar of a 2nd gear rolloff from 9K RPM of a desmo V-twin to moisten all nearby panties. No inline-4 will ever do that. :rock: