Drum Brake System: Description and Operation

This drum brake is an advanced leading/trailing shoe design. The advanced design operates with less total parts yet its performance is equivalent to other drum brakes while providing improved reliability. The operation and servicing of the advanced design brake is much simpler than traditional drum brakes.

This brake system employs a single universal spring to hold both shoe and lining assemblies to the backing plate and also act as the return spring for both shoe and lining assemblies. Force from the brake shoes is transferred through the fixed anchor and backing plate to the axle flange. Adjustment is automatic and occurs on any service brake application. Also, with leading/trailing brakes, it is normal for the leading (front) shoe to wear at a faster rate than the trailing (rear) shoe. Do not switch the position of shoes that have been in service as this may render the
self adjustment feature inoperative and result in increased pedal travel.

Important:
^ Replace all components included in repair kits used to service this drum brake.
^ Lubricate parts as specified.
^ Do not use lubricated shop air on brake parts as damage to rubber components may result.
^ If any hydraulic component is removed or disconnected, it will be necessary to bleed all or part of the brake system.
^ Replace shoe and linings in axle sets only.
^ The torque values specified are for dry, nonlubricated fasteners.
^ Perform service operations on a clean bench free from all mineral oil materials.