Ideal autox/racing wheel/tire sizes?

[spytech]

Hey all-

Finished my first full season of autox and did RA this last weekend and am looking to get new wheels/tires for track use.

My question is - what size wheels would be best, and what width tires? I am assuming 17" rims (probably will get the CCW blacks) - but not sure what width tires for up front (go with 315's in the rear). Did a search and saw that some guys are running 315's on all 4 corners on 17's - would love to get some feedback on this

Thanks!

[DJWorm]

It all depends on which class of AutoX you are intending on running

SCCA Super Stock limits you to stock size rims plus a +0.025" offset.
Most run CCW, Kodiak or Circle Wheels. Tire size is 275/40x17F and 305/30x18 rear. This helps front grip and rear traction marginally but car still has a lot of understeer.

A Street Prepared (ASP) allows you unlimited wheel/tire combination. Most of the top National Tour and Pro Solo guys rotate the SS rear 305/30x18 on 10.5x18 to the front and add 315/35x17 on 11-12x17 to the rear.

What this does is equalize the F/R contact patch area and reduces static, initial and mid corner understeer and makes the car tend toward neutral.
It also increases front turn in, grip, allows later braking, and the shorter side wall reduces flex, improves steering response and modulation. The more flexable rear side wall aids in traction on hard acceleration. This results in higher corner exit speeds.
This is a hot set up not only for AutoX but Solo I high speed and DE events

SCCA T1 allows either stock tire & wheel sizes or an optional 315/35x17 on all 4 corners with 11x17 on the rear and 10x17 wheels on the front. The 10x17 front wheel is a limiting factor and degrades the front grip of the 315 and is not optimal.

Although the T1 combination addresses some of the stock size short comings the ASP set up is actually faster on the road course.

If you are running a higher HP or larger cu. In. block then you may want to consider going with 335's in the rear. Bear in mind that these are actually too wide for AutoX as they can not be brought to optimal temps on the short AutoX course unless you have the HP to do so.
They are sometimes used on SM2 cars (higher HP) and can be beneficial to higher HP cars on a road course. They will induce more understeer but you may want that with the higher HP cars.

[spytech]

Thanks for the great reply, Dj.

I am consistently placed within the EM class (being supercharged and what not - but do not worry about what class I am in really - just like to have fun and compete for overall FTD). the 305/30-18f and 315/35-17r combo sounds interesting - never would have thought to use a bigger rim up front for a stiffer,smaller sidewall. I think I will go with that setup - thanks! Now I just need to take your advice for brakes before next spring