We'll there's a change bar next to it, and I'd never seen before so :dunno:

I knew about the 20mm tire allowance, that's why I asked the question. But since they're on 17" rims it doesn't really bring anything to the discussion.

the 17's with the 40 sidewall really give you some grunt coming out of a corner.
OD

So do the the 18"s we run:
Tire Size Sidewall Diameter Circumference Rev/Mile Difference
225/45-18 4.0 in. 25.97 in. 81.59 in. 777 0.0% Stock OE
245/35-18 3.4 in. 24.75 in. 77.76 in. 815 -4.7%
245/40-17 3.9 in. 24.72 in. 77.65 in. 816 -4.8%

No idea why they went that way.... Could be cost as they are a four car team. :dunno:

As far as weight the 245-40-17 Hoosier weighs 22 lbs and the 245-35-18 is 21 lbs. So I don't see a weight savings unless they can get a 17" wheel that weighs less than my 16.3 lbs 18X8 SSR comp. Only good reason I can come up with is cost.

Very true ULLLOSE-- the 35 sidewall 18" is just a little(insignificant amount) taller than my 235/40/17. I run road tracks and I like a little more sidewall than the 35 gives. I like a little more give when I hit the rumble strips and it seems that the 35 sidewall tire pressures rise faster than 40's (less volume?). Still they are dang good tires--wish Kumho would offer more sizes. 17's are cheaper all the way around. I run the enkei rpo2 wheel 17x8 and with my current RA1 235/40's my wheel/tire weight is 40lbs. Lug nuts and all. Aint the best but it aint bad either. Especialy since i got the wheels(new) and a qualifing set of the ra1's(lot's of 17"s out there) for a total of $700. Course I am playing and Ya'll aren't and that is what makes the differance.
rotor on
olddragger

Where do you find the used RA-1's? I'm trying to find a set of 18's. I know they are harder to come by than 17's, but I'm hoping when Spring hits it won't be too difficult to find a used set for track days. They'll be going on my spare set of stock rims.

18's can be found. Buy a copy of Grassroots Magazine and in the back there are listings for people that deal in slightly used race tires.
Good luck
Olddragger