I hear that on AWD cars you are supposed to keep all the tires within 2/32" of wear. Going with this, I recently bought a very gently used set of winter tires on wheels, and 2 tires have about 10/32" and 2 have 9/32". Based on how the tires wear on the AWD cars, where should I put the 10/32" tires to have them wear and catch up to the 9/32" tires.... Front or back?

Thanks

 

It's a rear biased AWD system so put the bigger ones on the back.

 

is the tolerance really within 2/32 between front to back?

 

In full-time AWD Subaru circles, some anyway, yes 2/32 is the breaking point.

In the occasionally AWD circles like our G37X's, no. Meatier tires out back will do fine and before OP knows it, he'll have even tread wear and can continue front to rear rotations to extend tire life.

 

I am looking at an M37x that the dealership is selling. They installed two new tires only, not sure why they would only install two instead of four. I understand that Infiniti system is rear bias, i was always curious to know what the tolerance was.

 

All I have found in my manual is that having a large difference front to back can trigger the AWD light..... There are no specific numbers mentioned.

Perhaps the 2/32" I am referring to came from tirerack.com

http://www.tirerack.com/tires/tirete....jsp?techid=18

Either way, I just want to try and keep them as close as I can.

 

Over 1% is looking for trouble with the AWD system. Running 245/275 tire combos with the AWD has been proven to have issues at high speed.

Let's do the math to see if your 2/32" difference matters. You have 2/32nds difference and there are 25.4mm in an inch, equaling 1.6mm difference. The stock tire diameter for our cars is about 26.9", which converts to about 683mm.

1.6/683 = 0.0023 = 0.23% difference < This is well within the safe limits for our car.

From my experience the tires wear slightly, only slightly, more on the rear wheels for the AWD G. I had even wear on my last set of tires with only one rotation. Your driving habits will make that vary obviously, especially if you like tire squeal.

 

I agree with the 1% difference but not sure of where you saw that there were issues at high speed. Care to support?

 

The linked thread shows a 1.1% difference in front and rear tire diameters resulting in a flashing AWD light above 80 mph. The problem went away after reducing the difference below 1%. The effect of the diameter difference increases with speed due to physics and all that fun stuff.

https://www.myg37.com/forums/g37-cou...red-setup.html

 

I see what you're saying.

However, after using a tire calculator, it seems that he was only .9% different and should have worked.

http://www.rimsntires.com/specspro.jsp

I used 245/35/20
9" width, +38 offset

275/30/20
10" width, +40 offset.

Am I missing something?

 

Speaking briefly of tire rotations...why is the cross pattern different for FWD vs RWD/AWD vehicles? In both cases, you're going to get a full rotation every 4th change. I don't see why they would suggest doing it differently.

 

I am assuming it's because of the pitch in the road, it's valuable to switch the sides of the wheels that were attached to the drivetrain. Especially cars that don't have an LSD to even wear.

 

Some tire manufacturers sizes vary slightly for a given tire size and that calculator uses the middle value. It's best to do the calculation manually using the manufacturers data if you plan to "push" the limits of the 1% ceiling.

In short, not all 245/35R20 tires are exactly the same diameter.

This can easily stretch that 0.9% over the 1% threshold. If you add in the fact that the rear tires start with a smaller diameter, and wear more quickly, it becomes clear that it can end up being a ticking time bomb.

 

Got it. I'm only asking because I would like to run a staggered set up on my M butif it's easier to go square, then I'll just go square. Less thinking involved.

 

Not only does staggered through off rotation patterns, so does having directional tires. These can only go fron to back and vice-versa (no cris crossing).