Abstract: A magnetic disk brake retractor is described as having a magnet mounted in the housing of a hydraulic disk brake and adjustable in position relative to a brake piston. In one modification described, the magnet is in the form of permanent magnets. The brake housing is constructed of a non-ferrous substance to prevent degradation of the magnetic field. The magnet is used to exert a force upon the piston to urge the piston to retract when the brake pedal is released. The position of the magnet is adjustable within the brake housing chamber to vary the strength of the magnetic field acting upon the piston and to also mechanically limit the amount of retraction permitted for the piston.