Drum Brake System: Description and Operation

This drum brake assembly is a duo-servo design. In the duo-servo brake, the force which the wheel cylinder applies to the primary shoe is multiplied by the primary lining friction to provide a very large force applied to the secondary shoe. Torque from the brake shoes is transferred to the anchor pin, through the backing plate and to the axle flange. Adjustment for both the primary and secondary shoe and linings is automatic during reverse brake applications.