Q: Is it mandatory to replace the rotors with a front brake pad replacement? 2010 BMW

Hi there - if the brake rotor is worn below a minimum rotor thickness (stamped on each rotor), then yes, it can be mandatory to replace the rotor. This is for safety reasons. If the rotor is grooved and requires surfacing for the new pads, and this machining results in a disc that is too thin, it cannot be re-used and must be replaced. Surfacing the rotor to make it perfectly smooth provides the maximum amount of surface area for the brake pads to engage - maximizing brake performance. In many cases, it is less expensive to simply replace the brake rotor, rather than machine it smooth. Worn brake rotor symptoms are as follows.