Drum Brake System: Description and Operation

OPERATION
The anchor plate drum brakes are duo-servo design. In the duo-servo drum brake, the force that the wheel cylinder applies to the primary shoe is multiplied by the primary lining friction to provide a very high force applied to the secondary shoe. Torque from the brake shoes is transferred to the anchor pin and through the backing plate, to the axle flange. Adjustment is automatic when the brakes are applied while the vehicle is backing up.