An apparatus and method for an electric bike retrofit for a disc brakes vehicle include an electric motor coupled with a rotor brake. The apparatus and method provide advantages in that the drive gear for the electric motor may be integrated with the brake rotor decreasing weight and minimizing necessary parts. The electric motor may mount to the existing brake caliper mounts and drive the brake rotor without the use of a chain, belt, or the like. Multiple gear ratios may be incorporated into the brake rotor allowing for shifting and increased efficiency of the electric drive system.