sccaGT1racer

I just purchased 4 18x10.5 rims off a c5 zo6 for my 08 base c6. That being said I want to get the maximum tire under the car without rubbing . I am looking at putting hoosier a7's on it but they don't offer a 305 18 for the rear. Will a 315 18 fit under the rear or should I just go square 285's?

randomus

I've run 315 A6's on the C5 Z06 rears at the front of the car. It does rub a bit at full lock so you have to be careful in the paddock. I've never had a problem on a course, even really tight ones. I bought spacers but have never used them.

Having that much tire in the front is really nice.

sccaGT1racer

Thanks for the help. I was starting to think this is some kind of top secret info.

hungryhippo

Depends on your ride height and spring rates/sway bars too. The rears will stick out a little bit.

sccaGT1racer

I ended up with a7 295's x18 square on the 10.5 rims. I heat cycled them yesterday with no rubbing issues on the road. I set up the alignment with -1.5 camber 7.6 caster .008 toe in front
-1.0 camber .000 toe rear
I didn't want to go crazy yet with the camber front toe out due to I still drive it on the street. The turn in with the square setup is night and day better. I hope to shave atleast 3-4 seconds off the stock times with street tires.

sccaGT1racer

I finally got my trailer registered so I could use the new tire and wheels. I would say I picked up a solid 3 seconds over my re11's 18/19 combo on our average 30-40 second autocross courses. I found that the car needs more negative camber in the front due to higher corner speeds from the tire wear. The car is going to be good when I get it dialed in on the a7's square.

sparkin3

Any concerns about oil pressure now you're able to pull more lateral Gs?

sccaGT1racer

I have seen no loss of pressure at this point but the courses I am running are very quick. There are no sustained corners where oil can be held away from the pickup due to G's.