I agree with Joe Snyder. The skinny tires will get too much side bite. Use the common width tires with a much harder compound if you're going to have a tire rule. Also, someone mentioned a "maximum" of 21.5 inches for spacing the RR. I would beg to differ and say make 21.5 a "MINIMUM" for spacing. Unless I'm doing something wrong, we move our RR "out" to loosen the car up.