RE: RC Tank F.A.Q.
Q: Is it important to break in a new motor?
A: Yes, it's important to break in a new motor to improve power output and reduce power consumption. A new motor comes with flat brushes and a round commutator as shown in the left diagram below. The goal is to wear the brushes down in such a manner that you have a curved surface (and thus more contact area) at the commutator/brush interface, as shown in the right diagram. If you try to break it in by simply running the tank at full load at the get-go, you create a lot of arcing which pits the surfaces and degrades performance.