dave-C2

I need to buy street tires that can serve as wet track tires for my newly acquired 6GT3.
The OEM tires 235/40 & 295/30 are diameters are 25.4 / 25 F/R. The rear is about 1.6% smaller than the front.
I am considering tires that aren't made in 295/30 so the rear may be 0.7% larger than the fronts.

What is the max allowable difference in tire diameter?

Should the front diameter be larger than the rear?

TIA

FFaust

Good of you to ask.

+/- 5% difference front to rear comes to mind before you start confusing the ABS, but I could be wrong. You will be fine with tires slightly larger in the rear, but try to keep it close.

mooty

245/35
245/40
315/30
I ran all above no issues

GentlemanRacer

Hey Mooty,

I am currently running the 315/30 18 nitto's 01 and I am getting a bit or rubbing of the fenders under load. These are mounted on fikse with Oem offsets. Am I In trouble re wheels or tires or camber?

85Gold

I run 315 NT01 with neg 2.2 rear with no running on stock offsets.

Peter

dave-C2

Thanks guys.
Mooty, the 245/40 & 315/30 combo has the R about 0.4% smaller than the F.
The 245/35 & 315/30 has the F about one inch smaller diameter than the R, about 3.5% difference.
Very interesting, thanks for the data.

GentlemanRacer

Dave, as above any of those combos work. Mine is probably camber related as Peter suggested. But this will probably be mute to me in 3-4 track days when my nitto's will be toast and I will start running 295 Rr Hoosiers