15" tires, soft tread for traction which equals shorter life but eliminates the problem of dry rot, stiff sidewalls for handling, getting what you pay for = Avon CR6ZZ. Street legal, radial carcass, Z speed rated tire for classic sports car racing (Cobras in particular) available in sizes up to 295/50R15 . Of course they are around $350 a tire, but what is grip worth?