Wheel size matter much?
 

Ok so help me out here. I know wider wheels and tires are great for autocross and road racing because you have better traction due to a bigger contact patch. But does it matter if you have 15", 16" or 17" wheels? Or should you have the smallest wheel that will fit? Lets say weight doesnt matter. I'm asking more about the diameter of the wheel if it matters any.

The taller a sidewall is, the more it will deflect. If you want more precise steering, less deflection is good.