The way a physicist might think about it, is to consider a balance of forces. All of the forces on an object, including inertia, add up to zero. For the object to accelerate, or to move against friction, the forces pointing in one direction must exceed those pointing in the opposite direction.

This corresponds to a slight increase of the tension on the "pulling" spokes, and a slight decrease of the tension on the remaining spokes. It's simplistic but I think it's accurate enough.