I've kept track of the various threads on the best tire/wheel setup for autocross on a C3 that does not have flares or offset TA's and I am considering my option and would like to know if anyone has tried a 285/40r17 on the rear.

I sounds like several forum members (Gordonm, gkull, Me2) report wheels of 17x8 4.0bs front and 17x9 4.5bs rear (E-brake cable moved to top of TA). It has been reported that these wheels are fitted with 255/45r17 (27.0" dia) front and 275/50r17 (27.8"dia). I have found the 275 tires difficult to find.

There are several manufacturers that make tires in the following staggered sizes: 255/45r17 (26.0"dia) front and 285/40r17 (26.0"dia). These tires also report superior cornering capability. The pace car had tires of 26.1"dia so the 26.0"dia might work. I'm concerned that the 285mm rear with 4.5"bs may interfere with the spring or sway bar. Some forum members have reported some interference problems with 285mm rear but the wheel bs was not specified.

My cheap backup plan for more traction is to go with the venerable BFG Radial T/A 255/60r15 (27.0"dia) front and 275/60r15 (28.0) rear with stock wheels at $75/tire and available in stock almost everywhere I look. The stock C3 225/70r15's are 27.4"dia.

Any advice on the 285mm and 26" dia would be appreciated.

 

Real racing wheels 16X9 4" backspace (parking brake cables re-located to top of trailing arm.) Kuhmo V-710 Victoracers 265-45-16 or Hoosier 275-50-16 AS06 tires (cold weather.) Wheel/tire weight about 37.5lbs. I my humble opinion if you want BIG diameter tires and wheels you don't understand the basic physics of Autocross racing and are already behid the proverbial 8 ball.

 

I'm running 295/35/17's on the rear on 9 1/2 inch torque thrust 2 rims. No sway bar and the E brake cable moved. Car is lowered to 27 inches from ground to top of fender opening. No problems.

 

Not sure if this is a option for you, and i know some people don't like wheel adapters, but. I am running a set of C5 size rims with 2.75" adapters in the front and 3.00" in the rear, with no rubbing issues and it was a HUGE increase in traction and stability. Plus rubber is really cheap because its the same size as the C5's. In the front i have 245/45/17 and in the back i have 275/40/18. I personally like the look of the combo but some like to see a little more dish on the wheels.

Ryan.

 

Are these dedicated track tires and wheels? Are you rule limited? Once you have some mods you jump up classes. This weekend I'm running 10 and 12 in RR slicks

 

On rear I'm running 285/40/18 Toyo's on 9 inch rim with 4 inch offset (so wheel is 1 inch further in than stock) rear track is same as stock. Tyres clear trailing arms (just) and inner fenders Sway bar rubbed so was removed, e brake brackets remained in stock position. This is with stock F41 suspension.