So I am noticing some wheel slip here and there on my 16 AWD S.
From what I can tell, and I have done 0 research on this, we are not a true AWD system.

Since I am lowered with an aggressive offset in the front, I am confined to a certain tire size in the front and running 275/30/20 with a soft sidewall to make it fit.
I was talking to a buddy of mine who mainly works on GTR's and was looking to put a 325/35/20 on the rear as I have more room back there (R888's).

He said GTR's are super picky on tire size and if we ran a 35 sidewall that wide on the rear and a 30 on the front, he is not sure if the car would behave properly as the GTR's do not.

Anyone have any experience with this? Would it set off TPMS lights etc?

Thanks in advance

 

your car wont be happy about that as with a 35 sidewall profile your overall diameter of the wheel and tire will be much more than the stock and front wheels. My understanding is that the car will realize a significant mismatch between the rotation of the front and rear wheels and throw errors. try to keep the overall diameter of the front and rear wheels/tires as close as possible.

with 275/30/20 you are looking at about 26.5" diameter
with 325/35/20 you are looking at 29" diameter

 

The AWD system also would be unhappy with different front/rear diameters.

 

those profiles are backwards. You want the 35 on front and 30 on the rear. That will provide similar tire diameters.

 

If you're running 20" Toyo R888's, aren't you going to be limited to running the 285/35 and 315/30 sizes?

 

even there, the disparity between the two diameters is too great to run on an AWD

 

Maybe for the F Type but a lot (and I mean A LOT) of GTR owners run this setup including my coworker and his Alpha 7 GTR. I honestly don't know much about AWD though other than the OD needing to be within a certain %.

 

I am contemplating putting Bridgestone's RE-71Rs on the car as this tire is delivering the fastest track times for streetable track tires on Porsche. Guys are reducing their track times by 2 seconds avg faster than the already quick Michelin Cup 2s. This would require me to go from 255s on the front down to 245s as that is the only size available in the RE-71s. It appears the rolling radius is nearly identical front and back so this should keep the AWD system happy.

Bridgestone RE-71R:

245/35R20 26 lbs. 8-9.5" Tread width: 9.1" 26.8" Rolling radius: 778

295/30R20 31 lbs. 10-11 Tread width 10.7" 27" Rolling radius: 772


This compares to the OEM P-Zeros:

255/35ZR20
(97Y) XL
J Jaguar 26 lbs. 8.5-10" Tread width 8.8" 27.2" Rolling radius: 763

295/30ZR20
(101Y) XL

J Jaguar 29 lbs. 10-11" Tread width 11.4" 27" Rolling radius:770


Are there any other alternatives that would still fit the OEM 20" rim, give more grip, AND keep the rolling radius front to back within 1-2 % ???

 

The GTR and the F Type use the same style AWD systems. Rear bias, front interaction only when necessary, clutch pack electronic center differential.

However in terms of keeping the vehicle happy, its mostly software related once you get past relatively equal tire sizes, so you can't really compare what GTR owners do to us. What's most important is to get matched diameters and go from there.