Drum Brakes vs Disc Brakes: Which is Better For Cars?

Drum Brakes vs. Disc Brakes

The main difference between drum brakes and disc brakes is that drum brakes are cheaper compared to disc brakes. Disc brakes offer high braking performance as they are technologically superior and advanced compared to drum brakes. In the following sections, we will elaborate on this in detail.

How Do Brakes Work

Before getting into the key differences between drum brakes and disc brakes, you need to understand the basic working principle of both braking systems. A disc and drum brake works on a common principle of friction and heat. The below points will give you a better idea about the working principle of brakes.

• A brake works by applying friction/resistance to a rotating wheel, and in turn, it slows down the vehicle/brings the car to a halt. 

• This process creates heat as a byproduct.

• The rate of braking, or the rate at which the vehicle can be slowed down, depends on the vehicle's weight, applied braking force and braking surface area.

• The braking rate also depends on how well a braking system converts kinetic energy (rotation of the wheel) into heat. 

• Similarly, the braking performance depends on how efficiently the heat is dissipated from the components involved in the braking system.

The basic principle of drum and disc brakes is the same. But when it comes to heat dissipation, the difference becomes pronounced. To understand it better, we explain the working mechanism of both braking systems in the following sections of this article.

What is a Drum Brake?

A drum brake refers to a braking system that uses a drum design on all four wheels, hence the name drum brakes. All the parts of the brake are fitted inside a drum that rotates along with the wheel. The key components of a drum brake include brake shoes, pistons, springs and a wheel cylinder.

Refer to the points below to understand the working principle of a drum brake.

The brake drum is attached to the wheel hub, and it rotates along with the wheel.

• The backplate holds vital components such as spring, wheel cylinder, pistons and brake shoes.

• Hydraulic fluid is used to transmit the inputs on the brake pedal to brake shoes.

• When you press the brake pedal, the hydraulic fluid exerts pressure on the wheel cylinder and moves the piston outwards.

• The pistons push the brake shoes, which makes contact with the drum to cause friction.

• The friction slows down the wheel.

• Once the brake pedal is released, the brake shoes move to the original position with the help of retaining springs.

What is a Disc Brake?

A disc brake refers to a braking system that uses callipers, brake pads, and a disc. It is far superior to a drum brake due to its design and working mechanism. However, it works on the same principle of slowing down a vehicle through friction. The main components of a disc brake are a disc rotor, calliper and brake pads. The below points explain the working principle of a disc brake.

• The disc rotors are fitted to the wheel hub. They rotate along with the wheels.

• The calliper is fitted on top of the disc. The calliper houses two brake pads on each side of the disc.

• Hydraulic fluid is used to transfer the inputs on the brake pedal to the brake pads.

• When you press the brake pedal, the hydraulic fluid travels from the master cylinder to the calliper.

• The pressurised fluid pushes the piston and, in turn, pushes the inner brake pad against the disc.

• The pressure caused by the fluid pulls the entire calliper, and it causes the outer brake pad to rub against the disc.

• With both the brake pads pushing against the disc, the friction generated slows down the car.

• Since the discs are exposed to air, they dissipate heat more quickly than drum brakes.

Difference Between Drum Brake and Disc Brake

Both drum and disc brakes work on the same principle of friction and heat. But there is a drastic difference when it comes to cost, design, performance and efficiency. The below table will help you understand the key differences between disc and drum braking systems.

Advantages of Drum Brakes

Here are the benefits of drum brakes in cars.

• Affordability: The manufacturing cost of drum brakes is lower due to the simple components and construction. It also reduces the overall cost of a vehicle.

• Requires less force: Due to the simple working mechanism of drum brakes, it requires less force to engage the brakes.

• Servicing is easy: The wheel cylinder of a drum brake is easier to service than the brake calliper on a disc brake.

• Integrated parking brake: The parking brake can be integrated into the rear drum brake of a vehicle. Hence, the parking brake does not occupy additional space.

Disadvantages of Drum Brakes

Below are some of the drawbacks of drum brakes in cars.

• Overheating: Drum brakes have poor heat dissipation due to their design. All the components are enclosed inside the drum. Hence, there is no proper ventilation. Overheating is one of the most significant disadvantages as it affects braking performance.

• Rusting: Due to closed assembly, the metal components can clog up with dirt, and it may cause rusting. It may reduce the performance of various components such as springs, pistons, etc.

• Wear and tear: Due to the poor heat dissipation, drum brakes often generate a lot of heat. Due to heat and friction, the brake components wear out quickly.

• Too many parts: A drum brake has too many mechanical parts. Hence, it amplifies the probability of a brake failure.

Advantages of Disc Brakes

Here are the pros of a disc brake system in cars.

• Compact yet powerful: Even small-size disc brakes offer a powerful braking performance. The feedback from the brakes is far superior to drum brakes.

• Better heat dissipation: The disc-shaped rotors, callipers and brake pads are exposed to the air. Hence, they never overheat. Modern vehicles are equipped with ventilated discs, which are even better at dissipating heat.

• No rusting: Since the brake components are not enclosed in a chamber, they do not clog up with dirt. Moreover, it’s convenient to clean the disc since it’s easily accessible. Hence, the possibility of rusting is low.

• Safer than drum brakes: One of the biggest cons of a disc brake is wheels locking up under sudden braking. But this problem is solved with ABS (Anti-Lock Braking System). ABS has made disc brakes a lot safer than drum brakes.

Disadvantages of Disc Brakes

Below are some of the cons of disc brakes in cars.

• Expensive than drum brakes: The manufacturing cost of a disc brake is high compared to a drum brake setup. Hence, it also increases the overall price of a vehicle.

• Brake bleeding is necessary: Air in the hydraulic fluid (master cylinder) can be a disaster as it can cause a complete brake failure. So, bleeding of brakes is mandatory during the service of brakes.

• Maintenance of brake fluid: You need to change the brake fluid at regular intervals. Failing to do so will result in poor braking performance.

• Easy to lock up the wheels: Without ABS, it's easy to lock up your car's wheels if you are aggressive on the brake pedal. It may result in you losing control of the vehicle.

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Drum Brakes vs. Disc Brakes: Which is a Better Choice?

To answer this question, let’s put it this way. Both the drum and disc brake systems are not perfect, and they have their own set of advantages. So, the combination of the disc (at the front) and drum (at the rear) is an ideal braking setup. That’s the reason why most modern cars come with disc and drum brakes.

Typically, 60-90% of the car’s braking power comes from the front brakes, and disc brakes are more than enough for that purpose. Hence, drum brakes are adequate for the rear wheels. Cost is another factor that’s in favour of this mixed braking system. Disc brakes on all four wheels would substantially ramp up the price of a vehicle. So, the combination of drum and disc brakes works best for a mass-market car intended for commuting.

Did You Know?

• American luxury car 1920 Duesenberg was the first production car to get hydraulic brakes.

• The 1967 Porsche 911S was the first production car to get disc brakes.

• In its early days, disc brakes were called plate brakes.

• The current Formula One cars feature the most advanced brakes in the automotive industry.

Also, read: Car suspension: How does it work?

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