How Brake Drums Work – Bendix Gives A Rundown

Though brake drums are an older braking system compared to the widely preferred disc brakes, they remain highly intricate. This complexity makes it advisable to leave their maintenance to skilled professionals.

A drum brake consists of 10 main components, the drum, backing plate, the wheel cylinder and pistons, the brake shoes, the adjustment screw, the hold down springs and the return springs. Drum brakes that act as the handbrake as well, will also include a brake strut bar and brake lever.

Brake drums operate on principles similar to disc brakes, using two brake shoes to create friction against the drum's inner surface to slow the vehicle. When the brake pedal is pressed, brake fluid flows from the master cylinder through the brake lines to the wheel cylinder inside the drum. This fluid pressure pushes the cylinder’s pistons outward, forcing the brake shoes against the drum’s lining and creating the friction needed to reduce speed.

As the drum brake is directly mounted to the wheel hub, this generates the friction required to slow the wheel's rotation and the vehicle's speed. The return springs within the mechanism work to reinstate the brake shoes to their original position once the brake pedal is released, while the hold-down springs on either side keep the brake shoes in place at their pivot point.

The adjuster screw at the bottom of the mechanism gradually unwinds as the brake shoes wear, to close any increased distance between the brake shoe friction material and the inside of the brake drum, allowing for a consistent brake pedal feel and braking response. The adjuster screw needs to be manually reset at every drum brake service.

The drum brake, which also functions as the handbrake, features a brake lever inside the drum that enables the brake shoes to operate independently of the hydraulic braking system when the handbrake is engaged. Positioned between the brake shoes and the brake lever on one side, the brake strut ensures even application of both shoes, providing balanced braking whenever the handbrake is used.

Bendix provides a comprehensive selection of brake drums designed for various vehicles, paired with high-performance brake shoes that deliver exceptional stopping power. Engineered for durability, they ensure low noise, minimal dust, and reliable performance, making them an ideal choice for any vehicle.

Bendix’s Ultimate 4WD™ range includes drum brake upgrade kits designed to improve stopping power for a variety of popular four-wheel-drive wagons and utility vehicles.