Why is there an indentation or “cut” on the side of my brake rotors?  Some brake rotors have what appears to be an indentation or piece of the rotor material removed from the edges, similar to the photo on the right.  In any case, this "cut" on the side of the brake rotor is actually meant to reduce something known as rotating unbalance.  People may ask the question above or even claim their brake rotor is irregular or damaged altogether.  In actuality, this characteristic about the rotor does not mean there is anything wrong with the rotor, but that the part was balanced or mill balanced.  

                                                                                                                                            Source:  bimmerfest.com

Rotating unbalance is the uneven distr...