how does your wheel turn the same speed as the rear end, should be a lower number, tires are the final ratio, they won't spin at the same RPM as the axles, that is why they can effect a cars performance,
Matt,

You better re-think that one. The tires are bolted to the axles (lug nuts, remember?). If the tires don't rotate at the same speed (RPM) as the axles, you just broke something.

The diameter of the tire does affect the acceleration and top speed, but only because a small tire travels less distance per rotation than a larger one.