Abstract: An improved structure for an electrical actuation mechanism adapted for use in a disc brake assembly includes an electrical actuation mechanism adapted to be secured to an inboard leg of the caliper of the disc brake assembly. The electrical actuation mechanism includes a housing, an electrical motor disposed in the housing, and a spindle disposed in the housing and operatively coupled to the motor by a conversion gear assembly which is effective to convert rotary motion generated by the motor into axial movement of the piston. The spindle includes a shaft and a piston which can be coupled to the shaft by a dampening structure. The shaft is operatively connected to the motor for axial motion thereof, and the piston is operatively connected to a friction pad for engaging a rotor attached to a wheel of a vehicle in which the disc brake assembly is installed. The dampening structure can be comprised of elastomeric material or a fluid filled chamber defined between the piston and the shaft.