Brake Drum & Shoes Working Principle


There are two types of braking systems; the disc braking system and drum braking system. Newer vehicles tend to 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.

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. 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?

6 Main Parts of a Drum Brake Systems and Working Principle

Well, the brake drums 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 brake drum. Below is a description of each of these parts:

Brake Shoes – As discussed, 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.

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 braking 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.

Brake Cylinder – Each wheel of a vehicle with a drum braking system will have a brake cylinder. You will usually find the cylinder at the top of the vehicle. The cylinder contains the braking 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.

Emergency Braking Lever – The drum braking system contains an emergency brake which is comprised of a lever and cable. When you pull the lever up, it causes the brake shoes to move away and keep the vehicle completely idle.

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.

Read also: Ceramic vs Metallic Brake Pads: Pros and Cons

Automatic Adjuster – When the brake shoes become too worn out, they will naturally move away from the brake drums. 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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