Why do wheels reduce the force of friction?
Friction is mostly caused by contact forces between one surface and another. Those contact forces are mostly due to instantaneous bonding that occurs between the surfaces. When a wheel ROLLS over the ground, no point touches the ground for very long. The time a patch of the wheel touches the ground is more or less instantaneous, so there is no time for those contact forces to arise. There is some friction because the wheel will partially compress the surface, but that is in general less than the friction that would be seen in sliding objects. Note, it is NOT based on surface area…otherwise a skidding object on wheels would have little friction as well.
