How Does the Drum Brake System Work in a Car? A Beginner’s Guide

Brakes are one of the most crucial components of any car, ensuring the safety of both the driver and passengers. The drum brake system is one of the two main types of brake systems used in vehicles. In this article, we will explore how drum brake systems work, discuss their key components, and explain their operating principles.

What are Drum Brakes?

Drum brakes are a type of brake system where braking force is generated by pressing brake shoes against the inner surface of a rotating drum. Unlike disc brakes, where brake pads clamp onto a disc, here the braking occurs inside the drum.

Key Components of the Drum Brake System

To understand how drum brakes work, it’s essential to know their main components:

1. Brake Drum – This is the rotating part attached to the wheel hub. When the driver presses the brake pedal, the brake shoes press against the inner surface of the brake drum, causing the wheel to stop.
2. Brake Shoes – These are two curved pieces of metal covered with friction material. The brake shoes are positioned inside the brake drum and push outward when the brake pedal is pressed.
3. Wheel Cylinder – Located between the brake shoes, it converts hydraulic pressure from the brake system into mechanical force, which spreads the brake shoes.
4. Return Springs – These components ensure that the brake shoes return to their original position after the brake pedal is released.
5. Handbrake Cable – In some drum brake systems, there is a cable that allows the activation of the handbrake. This cable works by mechanically spreading the brake shoes.

How Does the Drum Brake System Work?

The operation of the drum brake system can be divided into several key stages:

1. Pressing the Brake Pedal

When the driver presses the brake pedal, the master cylinder generates hydraulic pressure. This pressure is transmitted to the wheel cylinders at each wheel.

2. Transmitting Hydraulic Pressure

The hydraulic pressure causes the pistons in the wheel cylinder to move outward, applying force to the brake shoes.

3. Spreading the Brake Shoes

The brake shoes spread out and press against the inner surface of the brake drum. This creates friction, which slows the rotation of the drum, and thus the wheel.

4. Braking and Stopping the Vehicle

Due to the friction between the brake shoes and the brake drum, the vehicle starts to slow down until it comes to a complete stop.

5. Releasing the Brake Pedal

When the brake pedal is released, the hydraulic pressure drops, causing the return springs to pull the brake shoes back to their original position, away from the brake drum. The wheel can then rotate freely again.

Advantages and Disadvantages of Drum Brakes

Advantages

1. Durability – Brake drums are generally more resistant to wear compared to brake discs.
2. Protection from Dirt and Moisture – The drum design provides better protection from contaminants, which can be beneficial in harsh environments.
3. Lower Cost – Replacing and maintaining drum brakes is often cheaper than disc brakes.

Disadvantages

1. Less Effective Cooling – Brake drums have poorer cooling properties compared to disc brakes, which can lead to overheating during heavy use.
2. Weaker Braking Performance – Under very intense braking, drum brakes may be less effective than disc brakes.

Conclusion

The drum brake system is a proven and reliable technology used in many cars worldwide. Understanding how this system works can help in better vehicle maintenance and early detection of brake issues. Knowledge about brake drums and brake shoes is essential for any driver who wants to ensure maximum safety for themselves and other road users.