Drum Brakes
A braking system that uses wheel cylinders to force brake shoes outward against a rotating drum to slow the vehicle.
Drum brakes are an older style of braking system still used on the rear wheels of some modern budget vehicles and many trucks. The system consists of a hollow brake drum that rotates with the wheel, a backing plate that houses a pair of semi-circular brake shoes, a wheel cylinder, and return springs.
When the driver steps on the brakes, hydraulic pressure enters the wheel cylinder, forcing its pistons outward. This pushes the friction-lined brake shoes against the inner surface of the rotating drum, creating the friction necessary to slow the vehicle. When the pedal is released, heavy return springs pull the shoes back to their original position.
While drum brakes are cheaper to manufacture and make effective parking brakes due to their self-energizing action, they do not dissipate heat well. Under heavy or prolonged braking, heat can build up inside the closed drum, causing brake fade. They are also prone to water retention, which temporarily reduces braking performance.
Servicing drum brakes is more complex than disc brakes due to the numerous springs and adjusting mechanisms involved. Regular maintenance includes adjusting the shoe clearance and inspecting the brake shoes for wear and the drum for scoring.