Working of Drum Brakes in a Vehicle

By | September 17, 2014

Drum brakes are friction type braking system. These are mostly found in older vehicles. Drum brake is also called block type brakes. Drum brakes consists of a set of shoes or pads that create friction against a drum. These drums are connected to the rotating wheels. In this article let us discuss about the working of the drum brakes.

The primary components of the drum brake system are, a backing plate, brake drum and brake shoe assembly, the wheel cylinder, retaining clips and springs and automatic brake self-adjuster.

Backing plate

  • The backing plate which is made steel and it’s attached to the suspension or steering components by a bolts.
  • This backing plate is used to support the wheel cylinder, brake shoes and levers.

Brake drums and brake shoe assembly

  • Brake drums are fitted on the brake linings.
  • The brake shoe assembly consists of the steel shoe and the brake lining material.

Wheel cylinder

  • A wheel cylinder is attached to a backing plate.
  • The pistons push against the brake shoes to make contact with the brake drum to slow or stop the vehicle.

Retaining clips and springs

  • The brakes are held against the backing plate by retaining clips and springs.

Spring is used to retain the brake shoe to it’s normal position with respect to the backing plate.
Now let us discuss the working mechanism of a brake drum.

Working of drum brakes in a vehicle
Normally the drum brakes are self-actuated brakes. When you press the brake pedal, the piston present in the wheel cylinder pushes the brake shoes against the drum. The brake shoes come in contact with the drum when brake pedal is pressed.

Extra braking force is provided by the retaining clips & springs assembly. Due to this, the vehicles wheel slows down and after the friction between the brake shoe and the brake drum, the shoe must be pulled away from the drum when the brakes are released. This is mechanism done by the retaining clips & spring assembly. A wheel cylinder is placed backing plates, it’s used to monitor the retaining clips and springs assembly. The wheel cylinder works on hydraulic pressure. The hydraulic fluid is compressed by a piston in the wheel cylinder. Due to this piston motion the hydraulic pressure is pressurizes. These is all about the working of drum brakes.

Many cars and most trucks are equipped with drum brakes on the rear wheels and disc brakes on the front. Compare to disc brakes, drum brakes have more parts and they are harder to service. But drum brakes are less expensive.

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