Jim H.

Does anybody know what size (F/R) the Cup cars are running in Speed GT? Can't find it on the web or on Rennlist.

245/275?

245/305?

275/305?

275/335?

Thanks.

Z06

275/305?

cosmos

Tires

Grand Touring (GT): The tires used are the Toyo Proxes RA-1 race compound DOT-approved tire. The size(s) used depend on the GT car. The sizes used in the GT class are the 245/40/18, 275/35/18, 305/35/18 and 335/30/18

Jim H.

Thanks, Cos. I found that from the Speed site as well but still am not sure what combo Wolf Henzler was running when he won the last couple of races (or the other Porsche teams for that matter).

I imagine they're running 305s out back but am not sure about the fronts.

cosmos

I will ask.

I am guessing they run the 245 and 305 The reason being is that the CUP cars run a slighty taller rear and the 305 fits that bill.

We can NOT run the 305 REAR and the 245 FRONT.

The ABS gets all weird and shuts off.

We can run the 245 and 275.

Mr. C4

Could anyone find out what pressures (hot) they are running on the RA1's? Would be much appreciated!

Ciao,

Johannes E.

forklift

My RA-1s like 38-40 hot, 40 if possible. They get VERY squirrelly about 42 hot and will step out quickly, but at 40 they are great.

frayed

I was afraid of that as the rear 305/35 are 1" taller than stock. I had good luck with shaved toyos on my M3.

Jim H.

Cos,

Is the ABS shutting off heresay or does somebody here have first hand knowledge of a problem with a 1" taller tire? I've heard speculation about this in the past but haven't read a real post about anyone actually getting an ABS light due to varying tire sizes from stock. I wonder because my assumption would be that speed differentials would be what the ABS looks at rather than absolute values.

Cup cars don't run ABS?

NJ-GT

I tested a 245/35R18 (24.4") Hoosier and a 335/30R18 RA-1 (25.94"). In addition to that, my rear ride height is set to stock and the front is maxed out to the minimum. The Manthey front camber plates lower the car even more. No issue with the ABS but plenty of issue with stability.

mooty

i am confused, some can run 335 rear some can't even fit 305?
i really love the RA1's and would like to see what fits in a stock gt3.

We can run the 245 and 275.
__________
i did this in a C2. not sure 275 is enough rubber on gt3, though i never tried it on gt3.

frayed

I don't think its fitment that is the issue, nor is it width, its diameter and its affect on weight balance (as per NJ above) and ABS (as per cosmos). Those 305 toyos are 35 aspect ratio. We really need 30's (ie, 305/30-18).

analogmike

Wish I saw this thread an hour ago, I just put my driving gear bag in Wolf's car for transport to mid-Ohio. It's blue now!!! Sorry I don't remember the tire sizes but I think the wheels are wider than the stock GT3 cup wheels.

Wish him a change in luck, see you in Ohio!

cosmos

Me!!!

I have had the ABS kick off when I ran the 305's at Fontana. The problem is that it takes a bit for the ABS to actualy shut off.

The first few warm up laps its on, and then the Brake pedal gets stiffer and stiffer, I was told its the ABS pump computer and the Cars computer (yes two different programs) conflicting untill it just shuts off and you get a big red WARNING msg on the dash.

I don't know why NJ'd ABS did not shut down. But maybe he is not driving long enough at a big track, and its the short parking lot stints and also if its on the street, is he enagaging ABS for the system to care?

I don't know. I do know that I can't track them in a 305.


ps. I also am not sure if its the rear by itself, or if its a combination of the difference in aspect ratio. Like the front is set to X and the rear is set to a X and if you change one of them to X it's ok, if you just change one of them (front or rear) to Y that is where things get wacky.

85Gold

In AutoX I have run Hoosier 245/40 or 245/35 Fronts and 305/30 rears with no ABS issues. 245/40 and 305/30 have almost the same height ratio as the stock Michelin PS2's and should nor cause an ABS issue.

Peter