Originally Posted by
TejanoTrackie
Same thing, I think. If you were to ride behind a bike with an off-center rear wheel, the frame would be turned sideways, and you would see the front wheel offset from the rear. The front wheel would be turned slightly, and would be out-of-plane with the frame. As a result the rear wheel would be constantly turned relative the direction of motion, creating an unstable condition, which can be very dangerous at high speeds.
Perhaps you're right, but we're talking about a few mm of redishing, one way or the other. I had bikes with central threads un-aligned (but parallel) more than that. My personal experience is that it doesn't make any difference. Not with a few mm, in any case.