THE COMPONENTS OF DRUM BRAKES
The drum brakes, like disc brakes, have a master cylinder, steel brake lines, and
proportioning valve. Where drum brakes part from disc brakes in design is in the
secondary hydraulic system and friction medium.
Here’s how the parts list for drum brake systems differ from disc brakes:
- Wheel cylinders are attached to the backing plate to actuate the friction
medium called brake shoes. - Brake shoes are used instead of brake pads. These shoes are affixed to the
backing plate via anchoring springs. Return springs are located at the top and
bottom of the shoes to ensure that when the brake pedal is released, the shoes
return to their resting position. Also, drum brakes use an elaborate self-
adjusting system comprised of cables, cable tracks, self-adjusting star wheels,
and a lever to actuate the star adjuster unlike disc brakes, which simply rely
on hydraulic pressure to keep the pads tight to the rotors. Some four-wheel
disc systems do use a mechanical actuator for the emergency brake.