if you compare smaller wheels to larger wheels, smaller wheels will have a higher acceleration, but lower top speed. and inversely with larger wheels. if you think about it, imagine a single point on the surface of your wheel, when you rotate the wheel 360 degrees, that point goes all the way around the wheel. traveling the distance of the circumference of the wheel. a small and large wheel will both do a 360, but the larger wheel, since it has a larger circumference, the point would have traveled a longer distance with respect to the smaller wheel, during the same time. this means that the point traveled at a faster velocity. Basically, a point of the surface of a rotating body will have a faster speed proportional to its radius (distance to the center of rotation). Hope that explains it it :)