[Christ]

The smoother the wheel is, the less vortex it will create. I was incorrect in my earlier post, the dimples on the wheel pan would only serve to create a thicker boundary layer, no vortices.

You ideally want as small a vortex as possible on the wheels, since the vortex is created by the wheels acting like an inefficient fan, sucking/pushing air during rotation. The smoother the wheel's surface is, the less the rotation matters, and the more it acts like a smooth stagnant surface, which is desirable.