A lot of 4 cylinder cars run 13X8 inch wheels with some 225 or 235 tires. Maybe Beno will chime in on this. He runs a honda and has the exact tires I am talking about. Eric ran some on his VW before he moved away. Smaller is better. Screw worrying about shifting. At the most you will shift 2-3 times on a course but you will get the advantage of those 225-235's on every corner and the reduced gearing will help you come out of every corner faster as well. That is what you need to consider. The wheels I am referring to are called "Kiaser's" Dont know how they are spelled but they are super light and not intended for anything but racing.