How Do Drum Brakes Work?

How Do Drum Brakes Work

We all know the great importance of the braking system in any automobile. For one, it helps bring a vehicle or motorbike to a stop which helps reduce the level of accidents when driving. 

But have you ever wondered: how do drum brakes work? This is a question worth asking, as someone who has driven an automobile before, be it a car, bicycle, or motorcycle. 

In brief, the brake drum works with the help of the brake shoe, which is designed to accommodate expansion in either direction.

Friction is created between the brake shoe and the drum whenever the brake lining of the shoe contacts the inner surface of the drum.

This prevents the vehicle from moving if the brake shoe is applied to the drum.

Indeed, it is physically impossible to operate a car without brakes. Brakes are essential to bring a vehicle to a safe halt and maintain control when driving. 

The vehicle’s handling may be improved to a more significant degree with the use of an appropriate braking system. Drum brakes are often only found on the rear wheels of contemporary automobiles.

On the market, one may choose from a wide variety of options for braking systems. But I’m going to talk about drum brakes and how they operate in this article.

Before we consider how do drum brakes work, we need to have a solid understanding of its many components and the roles that each of them plays.

Components of the Brake System

Before considering the answer to the question, how do drum brakes work? Let us take a look at the various components of a brake system. 

The rear plate of the wheel is fitted with the whole drum brake system so that it may be used.

The rear plate does not move along with the wheel in any way. Therefore it is permanently fixed in place.

1. Brake Drum

It is a circular housing made of cast iron used in conjunction with brake shoes to bring the vehicle to a halt.

The wheel’s hub is where the drum brake is attached through bolts. It spins around the corner along with it.

2. Wheel Cylinder

It is used to apply the brakes to push the brake shoe in the opposite direction. A connection has been made between the wheel cylinder and the master cylinder. 

When the brake is applied, it causes the piston inside it to travel outward, forcing the brake shoe closer to the inner surface of the drum.

3. Retracting Spring, Also Known as the Return Spring

After using the brakes, the brake shoe must be retracted using this mechanism. In a drum brake, there will be two return springs; one for the primary shoe and the other for the secondary shoe.

4. Self Adjuster

It keeps the distance between the brake shoe and the drum at its bare minimum, ensuring that they do not come into touch with one another while the pedal is not depressed. 

If the brake lining wears out and the space between the shoe and the drum rises, it is possible to readjust it so that the distance between the shoe and the drum’s inner surface remains the same.

After being adjusted, it will continue to have the same gap even while the brake is operating on its own.

5. Brake Shoe

It is the portion of the drum brake that is responsible for the friction, and the operation of the brake would not be possible without it. The outside curve of the brake shoe contains a lining for the brakes. 

During the process of stopping the car, the brake lining is the component that comes into contact with the braking drum. There are two categories of it.

(I) Primary Brake Shoe. “primary shoe” refers to a shoe with significant lining material.

(ii) Secondary brake shoe The shoe with a relatively modest amount of lining material is referred to as the secondary shoe.

Principle of Operation

Considering how do drum brakes work, we also need to take a look at the working principle of drum brakes.

The brake shoe may stretch in either direction without being restricted. Friction is produced in the space between the brake shoe and the drum whenever the brake lining comes into contact with the inner surface of the drum. This prevents the vehicle from moving in the forward direction.

How Do Drum Brakes Work?

Below is a breakdown of how drum brakes work. Number 4 will amaze you. 

  1. When force is applied to the brake pedal, the fluid in the master cylinder is forced into a more compact state, which in turn permits the piston in the wheel cylinder to move farther outward.
  2. The brake shoe is forced outward against the brake drum due to the piston in the wheel cylinder moving in an outward direction.
  3. When the lining of the brake shoe makes contact with the drum’s inner surface, the wheel’s motion slows down, and the vehicle stops due to the friction created between the brake shoe and the drum.
  4. When the power applied to the brake pedal is released, the springs that retract the brake shoe are activated, resulting in the friction lining and drum no longer touching one another. Now, the brake is ready to be applied once again.
  5. There is a screw that adjusts itself at the bottom of the assembly, and it is employed to keep the distance between the brake shoe and the drum as small as possible.

When the lining of the brake shoe begins to wear out, the gap between the drum and the brake shoe will rise. When this occurs, the adjuster needs to be readjusted to keep the gap at its smallest possible setting.


Since we’ve given an answer to how do drum brakes work, we are going to also look at the benefits.

They are a self energizing braking system. It indicates that they are built with the capability to function independently. It is less expensive than the braking method that uses discs.


  1. The difficulty with heating is that the friction region is entirely covered by lining, which means that any heat generated from the friction cannot escape into the surrounding air. Because of this, the vehicle’s braking performance may suffer.
  2. If the drum brakes become soaked with water, they won’t function as they should anymore. This is because it takes more time for the water to emerge from the drum. Because of the water, the friction between the brake lining and the drum is decreased.

Why Do New Cars Still Have Drum Brakes?

Drum brakes on the rear wheels are still widely used because of their cheap production cost and ease of installation.

Due to the reduced number of components needed, drum brakes may be manufactured at a lower price. Drum brakes, unlike disc brakes, may be used for stopping and parking.

What is the Biggest Problem With Drum Brakes?

The design problems of drum brakes are significant since they are prone to overheating, need more time to dry, and are often heavier than disc brakes.

Disc brakes are not suitable for parking since their size increases when heated and decrease when cooled.

Do Drum Brakes Use Brake Fluid?

The master cylinder may be accessed using this brake paddle. The braking fluid also serves as the operating fluid in this master cylinder.

When the brake pedal is depressed, more force is applied to the brakes by increasing the pressure in the braking lines.

Final Wrap Up

In this post, we have been able to answer the question of how do drum brakes work, their key components, and how they function.

We also discussed the benefits and drawbacks of using drum brakes. If you found this post helpful, please don’t forget to share it with your friends.

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