I've been poking around at a few different setups. Some people say that you need to have four wheels with the same tire sizes on full time AWD vehicles like the WRX.

But some people run different sizes on the rear (wider), both wheels and tires (18 x 8.5 with 18 x 9.5 rear)

Does it matter? Is this Subaru only? What about Audis with their quattro?

Thanks in advance with your thoughts.

 

I've been looking into this lately. First off, our cars generally understeer unless you've taken massive countermeasures. So if you're gonna stagger, you will want the extra meat up front. Doing otherwise is very rice-tastic. Sway bars, etc are a more logical way to accomplish this.

The main idea is that the circumference of all 4 tires should be the same to within a certain tolerance for AWD systems (Subaru, Quattro, etc). I believe I found the tolerance to be 2/32" for Subaru/Impreza in a NASIOC forum, but need to confirm.

I have a set of 18x8" rims with staggered tires (245/40 up front and 235/40 in the rear). I bought them used recently and planned to ditch the tires anyway, but was curious if it would work without toasting the diff on my WRX.

I jacked the car up with these wheels on last week and measured the outside tire circumference. The fronts were 1/8" longer in track than the rears, which is about double the WRX tolerance (if that number I cited is right).

Most forums are very anti-stagger for our cars, and I agree. It's way too much trouble to try to match tire circumference, etc, especially when the tires often measure different from the size indicated. Not sure if the difference in rotational inertia between front and rear puts stress on the diff.

 

it appears it is all for show then. the quattros have a tendency to understeer as well.