jpurban

I'm thinking of buying wider 9" front wheels and stepping up the tire width, but I know the AWD requires similar circumference on front & rear.

But what I don't know... What is the acceptable difference in circumference to avoid differential damage?

The stock 225/40-18 and 295/30-18 are within 0.5%.

245/35-18 and 295/30-18 are within 0.9%. Is this okay? Anyone run this set-up with AWD?

Thanks for the help.

rmc1148

On 6sp there are numerous recent threads that will tell you all you ever wanted to know lol.

"02996ttx50

the two optimal tire size choices are the same as porsche intended for the turbo and the gt2 respectively. if i were you, i'd match the 9" front with a 12" rear and run 235/40/18 and 315/30/18 per gt2 and faggeddaboudit.

Spec Sidewall Radius Diameter Circum Revs/Mile Difference
225/40-18 3.5in 12.5in 25.1in 78.8in 804 0.0%
235/40-18 3.7in 12.7in 25.4in 79.8in 794 1.3%
295/30-18 3.5in 12.5in 25.0in 78.4in 808 0.0%
315/30-18 3.7in 12.7in 25.4in 79.9in 793 1.9%

the 315 has a diameter of 25.5". The 295-30 is 25.1" the 235- has 25.4", and the 225-40 is 25.1"


this is the only set of specs i still have/use. there was a very comprehensive thread/spreadsheet for all compatible pcar tire size/offsets incl rev per mile differences, but i'm unable to find it. sorry. you might find it with a search

jumper5836

Only problem with going with 235/40/18, 315/30/18 combo is that there are no R compound tires. I stay with stock becuase I can run MS PS cups which provide way more grip then putting on wider tires.

"02996ttx50

i have been running ps2's religiously, but point taken. beyond that i see that size combo as a solution esp with the 9 in front

jumper5836

I wonder if we could run 245/40ZR19 on 9" wheel and 325/30ZR19 on 12" wheel with Michelin Pilot Super Sport tires.

powdrhound

Nitto NT01s come in this size. I've been running this size on 9/12" wheels for several years. Probably the best bang for the buck R compound out there. Good to the cords..

powdrhound

Won't fit

jumper5836

so what size are your running with the nitto's?

powdrhound

235/40/18 and 315/30/18

I'm on my 10th set right now over the last two years. Actually heading to the shop to grab another set of rears. Great tires.

jumper5836

Thanks, I am going to start doing the same. The tires sound like they can stand more heat cycles and they are wider then the cups.

PAULUNM

I agree- I'm running GT2 sized PS2s. Much better ride quality and grip than the turbo sizes. Safe for your AWD system as well.

powdrhound

Unlike the Cups, heat cycles are not an issue on the Nittos. They're good to the cords. I'm switching NT01 sizes to 245/40/18 and 305/35/18, obviously not an AWD set up. Just ordered 2 sets. $912 per set out the door...

jumper5836

What offset are you running on the 12" rears? Tried them on the stock 11" and they don't work. Also did you roll the fenders?

powdrhound

I run the NT01s on 18x12 ET41 without any issues. I have also run them on 18x12 ET44 without any problems. Rear fenders are rolled. My friend now has my old ET44 wheels with 315/30/18 PS2s and has zero issues even though his fenders are not rolled.