ATX_Native

I had issues with grip levels in the rear on the 265’s.

So if the date codes on the tires are newish and you’re having grip issues, you could always buy a set of rears to match the fronts but in 285/295.

Ended up finding a pair of 285/35-18 PS4S tires that were 1 year old and full tread off eBay for $350 shipped for both.

So that was a cheap upgrade, brand new the rears were ~$900.

carguy999

Is an inch circumference change normal? Both are OEM spec sizes:

19s
-- 235/35 19
-- 295/30 19

18s
-- 235/40 19
-- 265/40 19

Using a size calculator I see the front total circumference doesn't change a lot (.25") but the rear total changes by over an inch (1.2 inches bigger with the 18s).

Front


Rear


Is that normal? The overall difference in circumference isn't much different front to rear:81.56-80.05 = 1.51
Average = 80.80

So 1.86% difference in overall circumference between wheels on the old 19s, but if we do the same math for the 18s82.75-79.8=2.95

(82.75+79.8)/2=81.2750

(2.95/81.275)*100=3.6297

We wind up with 3.6% difference between front and back. Seems like a lot, and I've seem comments where that might upset ABS or other systems?

ATX_Native

^ it’s what Porsche put on the car so yeah, it’s ok.

I run a 285/35-18 on the back and I haven’t died yet.

Also some people run a 325/30-19 out back.

Thee are lots of different tire sizes you can run.

I believe the full of thumb is no greater than 3% split between front and rear on AWD cars.