Rim sizes?

[CVD]

As far as I am concerned the wheels only NEED to be big enough to clear the brakes, and I would never go more than 1 inch larger than factory size. Come to think of it, I never have gone over factor size wheels and probably never would. In my experience the handling benefit is effectively nil. Wheel weight, tire choice, and driver all have far more to do with it. Having a stiffer, shorter sidewall is not always going to be a good thing. In fact, from what I have seen in autox it tends to be a bad thing.

And if you are thinking about light track duty, your next thought should be AWD brakes.