Originally Posted by
Doge
They don't. The front turns faster.
Assuming tires are same diameter, try this. Line up both wheels valve stem's at the bottom. Ride around the block. When you get back both valves should be in the same O'clock spot unless one is spinning faster.
I'm pretty sure this does not happens while moving in a straight line. I think as one turns, the front wheel has to complete a bigger circle (distance) than the rear. So you would want a lighter front wheel if it is going to do a bigger diameter circular movement. A constant speed through a circular path is still a form of acceleration.