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Old 07-09-2008, 05:56 PM   #1
txl146
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Default How much tire off-set is allowed on AWD car?

I have noticed recently that RR tire has about 1 - 1.5 /32" more tread compared to other 3 tires. I haven't noticed anything unusual in terms of drivability or handling-- I am fully aware that it is not an ideal situation for AWD drivetrain.

Any recommendation as to what I need to do aside from getting one used tire?

Thanks,
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Old 07-09-2008, 07:14 PM   #2
illini_wrx
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i think 1/16th is the threshold, so you're okay.
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Old 07-09-2008, 08:02 PM   #3
fiveoh88
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subaru is nuts...the tolerance they call for in all four tires is almost impossible to assure

something like a few psi difference in a tire can cause the tire to be out of tolerance...

theres been a bunch of threads on this with a split of people saying OMG don't run a tire with more than 1/32" difference tire tread than the others, and the rest saying that subarus tolerance in tire diameter is nuts and is almost impossible to do
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Old 07-09-2008, 08:52 PM   #4
Howl
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Subaru recommends 1/8" circumference difference. Circumference is easier to measure than height or tread depth because the difference will be 3.14159 times larger. Jack up a corner and run a rope around the tire then measure the rope. Repeat for each corner.
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Old 07-09-2008, 11:44 PM   #5
txl146
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Just measured again across all 4 tires. Biggest difference is about 1.25/32" so I would think that I maybe okay. Not so sure though..

Last edited by txl146; 07-10-2008 at 12:08 AM.
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Old 07-10-2008, 09:06 AM   #6
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I happen to run across this question quite often as people occassionally have to replace 1 tire. I have spoken with several people in the know when it comes to the Subaru AWD system and they say 3/32 - 4/32 is acceptable. On another note they also say that "the owners manual was written with to much influence from the legal department".
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Old 07-10-2008, 09:36 AM   #7
xaznxeclipsex
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I have a theory: take out 1-3psi of air from the other 3 tires to compensate the 1 tire that has less thread. Wouldnt this even out the circumfrerence? And maybe even over time the other 3 tires with less air pressure will wear out a bit faster then the 1 tire with correct air pressure, when that happens just put all tires to the correct PSI.

Would my theory work?
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Old 07-10-2008, 12:52 PM   #8
Luke@tirerack
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theoretically it would but, any change in vehicle weight would alter the theory as it would cause a change in the static loaded radius
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Old 07-10-2008, 03:21 PM   #9
DiscoGsus
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Actually, it wouldn't work.
The higher inflated tire would either wear more in the middle of the tread or remain unchanged, but the under-inflated tires are going to wear at the outside edges of the tread. Not to mention that just sounds like a bad idea in general.

To answer the OP, move that tire. Switch the backs L <-> R and see if it happens again to whatever tire is in that corner.

Ever check your alignment?
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Old 07-10-2008, 03:22 PM   #10
txl146
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Quote:
Originally Posted by Luke@tirerack View Post
I happen to run across this question quite often as people occassionally have to replace 1 tire. I have spoken with several people in the know when it comes to the Subaru AWD system and they say 3/32 - 4/32 is acceptable. On another note they also say that "the owners manual was written with to much influence from the legal department".
3-4/32 seems huge in tire wear difference... !
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Old 07-10-2008, 10:21 PM   #11
Miroshnichenko
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My family has owned 8 subarus that I can remember, many times they had different tires front/back... and most of the time they had different amount of tread left... we've NEVER had a problem, not even in the newer 05 Legacy 2.5i and 05 STi

..I think subaru exagerates.
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Old 07-12-2008, 04:01 PM   #12
txl146
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Hope that really is true...
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