6 Parts of a Drum Brake System (and What They Do)

There are two types of braking systems; the disc brakes and drum brakes. Almost all newer vehicles have the disc braking system because it is more heat resistant and does a better job of slowing the wheels down.

Brake drums and shoes represent the classic braking system which was used in older vehicles. However, there are still some vehicles which use the drum braking system today. It is a relatively cheaper braking system that can better accommodate bigger vehicles like trucks.

What Are Brake Drums and Shoes?

The brake drum is basically the equivalent of a brake disc just like the brake shoes are the equivalent of brake pads. The drum braking system uses the brake shoes as its version of brake pads. The brake drum looks more like a bowl than a flat disc.

There is one brake drum connected to every wheel of the vehicle or just the rear wheels have drums while the front wheels have rotors. As for the brake shoe, this is what pushes against the spinning surface of the brake drum.

Together, they create the necessary friction needed to slow down the vehicle. Sounds pretty simple, right?

How Brake Drums Work

6 Main Parts of a Drum Brake System

Drum brakes take a lot more work to maintain because they are comprised of several more components than brake discs. In fact, there are a total of 6 parts which make up the drum brakes. Below is a description of each of these parts.

1. Brake Shoes

As mentioned above, brake shoes serve as the brake pads of the braking system. They contain the brake lining which pushes against the brake drum to create friction.

This is the friction which slows down or stops the vehicle. When the brake shoes are installed, they cannot be touching the brake drums. However, they need to be as close to them as possible.

2. Brake Pistons

Brake pistons are responsible for pushing the brake shoes onto the surface of the brake drums so that they make contact. This is done after brake fluid adds pressure to the pistons.

If your brake shoes are positioned too far away from the brake drums, then it will put more stress on the pistons because they will need to push the brake shoes farther to reach the brake drums.

3. Brake Cylinder

Each wheel of a vehicle with drum brakes will have a brake cylinder. You will usually find the cylinder at the top of the wheel.

The cylinder contains the brake fluid which it sends to the two pistons inside of it. This is how the pistons are able to push the brake shoes into the brake drums and slow the vehicle down.

4. Emergency Brake Lever

A drum braking system contains an emergency/parking brake which is comprised of a lever and cable. When the driver pulls the lever up, it causes the brake shoes to move away and keep the vehicle completely idle.

5. Brake Cable

The cable is what connects the emergency brake lever to the brake shoes of the braking system. You need to ensure this cable stays functional because it is the main component of the emergency braking mechanism.

If it were to snap or get damaged, then you would not be able to park your vehicle with the emergency brake on. This will end up putting more pressure on your brake drums and brake shoes.

6. Automatic Adjuster

When the brake shoes become too worn, they will naturally move away from the brake drums since there is less material there. This will cause the brake pedal to easily drop to the floor as you step on it.

The job of the automatic adjuster is to stop this from happening. There is an adjuster connected to the brake drums which will bring the two components closer together if it detects this separation taking place.


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