The primary components of the drum brake system are: the backing plate, the brake drum & brake shoe assembly, the wheel cylinder, retaining clips & springs and automatic brake self-adjuster.
The drum brake system operates by forcing the friction-lined brake shoes against the inner surfaces of the rotating drums. The shoes are designed to operate with a self-energizing action.
The brake lining is a specialized friction material, riveted or bonded to a steel shoe. The shoe transfers the wheel cylinder movement and forces the lining against the rotating drum.
The backing plate is bolted to the axle housing or suspension member. It provides a mounting for the wheel cylinders and brake shoes to act against the rotating drum.
The wheel cylinder and piston react to hydraulic pressure from the master cylinder, and the outward movement of the piston forces the shoe and lining against the drum.
