Team Ackodrive9, Sep, 2021
The braking system is the most prominent component for the safety and reliability of a car. The safety of the passengers, motorists on the road, and pedestrians are hinged on a vehicle's brakes. There are mainly two types of brakes in the automobile industry: drum and disc brakes.
Both the brakes are used in modern cars, and they work on the same basic principle. So, what's the difference between both braking systems? Read on, as this article answers all your questions related to drum brakes vs disc brakes.
Before getting into the key differences between drum brake and disc brake, 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 by product.
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 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 the braking systems in the following sections of this article.
Drum brakes are the early automotive brake systems, and they use 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.
A disc brake 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 fuel is used to transfer the inputs on the brake pedal to 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.
|Parameter||Drum brake||Disc brake|
|Construction||The components are housed inside a drum.||The components are exposed to air.|
|Design||It uses a cylindrical drum and brake shoes.||It uses disc-shaped rotors and brake callipers with brake pads.|
|Cost||Affordable than disc brakes.||Expensive compared to drum brakes.|
|Performance||Slow response to the inputs (brake pedal).||Instant response to the inputs (brake pedal).|
|Efficiency||Heat dissipation is poor.||Better heat dissipation.|
|Operating temperature||Performance drops at high temperatures.||Performance remains the same even at high temperatures.|
|Maintenance||Difficult to repair or replace the brake shoes due to complex design. However, the maintenance cost is low.||Easy to repair or replace the brake pads due to the simple design. However, maintenance costs are high.|
|Application||It is used in heavy vehicles (trucks, buses, etc.), cars and scooters/bikes.||It is used in modern cars, bikes and scooters.|
Here are the advantages of drum brakes.
Affordability: The manufacturing cost of drum brakes is lower due to the simple components. 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.
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Below are some of the disadvantages of drum brakes.
Overheating: Drum brakes have poor heat dissipation due to their design. All the components are enclosed in a cylindrical 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 pretty quickly.
Too many parts: A drum brake has too many mechanical parts. Hence, it amplifies the probability of a brake failure.
Here are the pros of a disc brake system.
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 in dissipating the heat.
No rusting: Since the brake components are not enclosed in a chamber, they 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 with new technology: 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.
Below are some of the cons of disc brakes.
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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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 the best for a car intended for commuting.
Here are some of the most frequently asked questions related to drum brakes vs disc brakes.
Car manufacturers generally use drum brakes on the rear wheels of most entry-level and mid-range cars. The reason is to keep the overall cost of the vehicle in check. Moreover, for the performance of a regular car, a drum brake is more than capable of serving the purpose, that is, providing adequate braking.Do disc brakes offer better braking performance than drum brakes?
Yes, disc brakes offer way better braking power than drum brakes. That’s the reason why most cars are equipped with disc brakes on the front wheels.Is it difficult to change the brake shoes of a drum brake?
Yes, it is a complex job to change the brake shoes of a drum brake. Since all the components are enclosed inside the drum, it is hard to access the parts and replace them.
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