Originally Posted by microed

Generally speaking, the larger diameter rotor is going to give you a little more torque (punch) and the smaller diameter rotor will provide more RPM. So if you were running on a small to medium sized track, the 12.5 rotor would likely yield slightly faster lap times depending on the layout. If the track is on the larger side or not very technical, the 12.3 might yield faster lap times due to it's slightly higher RPM.

So if I were just going to bash around in large parking lots, I would probably get a motor with a 12.3 rotor in it.

Does this answer your question?