Drum Brake System: Description and Operation

This drum brake assembly is a leading/trailing shoe design. Both brake shoes are held against the wheel cylinder pistons by the upper return spring and to the fixed anchor plate by the lower return spring. When the brakes are applied, the wheel cylinder pistons move both shoes out contact the drum.
With forward wheel rotation, the forward brake shoe will wrap into the drum and became self-energized.
With reverse wheel rotation, the rear brake shoe is self-energized. Force from the brake shoes is transferred to the anchor plate through the braking 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 front shoe to wear at a faster rate than the rear shoe.