Disc brakes vs drum brakes – A comparative analysis

Disc brakes vs drum brakes

The braking system in any vehicle is undoubtedly the most important safety feature which helps you stopping or slowing down the car as well as manoeuvring the vehicle in a controlled manner. With the passage of time, braking systems have improved a lot with improved technology, but the basics remain the same. In Pakistan, most of the cars are usually equipped with front disc brake brakes accompanied with rear drum brakes. Why manufacturers follow this sequence of braking system? Which braking system is better? How do they work? We will make a comparison of the two braking systems in this article.

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When a car is moving, it has a certain amount of kinetic energy. This energy needs to be removed in order to stop the car. Since energy can only be transferred from one form to another, the kinetic energy is converted into the heat generated by the friction when the brakes are applied.

brake glow

How Do They Work?

Disc braking system consists of brake pads, the calliper and a rotor. The calliper has a piston inside it while the disc-shaped metal rotor is mounted to a hub. When brakes are applied, calliper squeezes the brake pads against the spinning disc. This process provides enough friction to slow down the vehicle. The slowing down of a car is directly proportional to the amount of pressure applied to the brake pedal. Apply enough force on the brake pedal, and the wheel will lock.

disc-brake-diagram

Drum braking system consists of brake shoes, hydraulic wheel cylinders and a brake drum. Brake shoes are curve shaped with friction material lining on the inside. This system works on the same principle as well. When force is applied on the brake pedal, the brake shoes are forced against the inner sides of the braking drum by hydraulic wheel cylinders. As a result, friction is produced which helps in slowing or stopping down the vehicle.

drum-brakes

There are several factors we need to consider while making a comparison between the two braking systems. A few of them are given below:

A) Performance:

When it comes to the performance of the two braking systems, disc brakes dissipate heat much more effectively. Brakes lose their effectiveness with the passage of time due to brake fade. Brake fade occurs at a great extent while driving on a steep descending terrain. Disc brakes experience less brake fade as compared to the drum brakes because they are capable of dissipating heat more efficiently. Moreover, driving becomes really hard with drum brakes in the rainy season because it collects water inside which reduces the braking ability.

B) Maintenance Cost:

The drum brakes are designed in a way which is very convenient to replace as compared to disc brakes. Regarding repair work, the brake shoes can also be easily replaced at a nearby mechanic. It takes very less time as well. A much less maintenance cost is involved in drum brakes due to the ease of repair or replacement. The parts are inexpensive as compared to the disc braking system. However, drum brakes usually require some adjustment when changing the brake shoes whereas it is not required in disc pad replacement.

C) Easy Inspection:

It is easy to inspect disc brakes for any wear and tear. There is no need to remove the tire in order to make disc inspection. You can actually see how much material is left on the disc pad from the outside. But for drum brakes, you need to take the drum off to see how much material is still there on the shoe. The tire needs to be removed while inspecting the brake shoes of the drum braking system which takes a comparatively longer time.

D) In terms of Safety:

Both braking systems are supposed to slow down or stop the car as per requirement. But when it comes to the safety of passengers inside the car, disc braking system is far better than drum brakes. Although the drum provides more initial braking power, but the disc brakes can provide consistent braking power throughout its operation. The drum brake will heat up quickly after intense braking and lose its effectiveness. All-wheel disc brakes are the best option to choose if you are very much concerned about the safety but disc brakes just on the front wheels works fine as well. It all depends on the requirement of the consumer as well as the cost.

Why manufacturers mostly use front wheel disc brakes?

In Pakistan, most of the cars manufactured consist of a front disc and rear drum brakes. Cars like Honda Civic and Toyota Corolla come with 4-wheel discs whereas smaller sedans like Honda City and hatchbacks like Suzuki Swift, Cultus and WagonR come with discs in the front and drums in the rear. This sequence is followed due to the economics involved in the manufacturing. The weight of the car shifts in the forward direction when brakes are applied. Around two-thirds of braking effort occurs in front of the car due to the engine and body weight towards the front. Most of the braking is done by the front wheels using disc brakes leaving not much work to be done by drums on the rear wheels.

If you are concerned about the safety of the car and passengers sitting inside it, prefer a vehicle with disc brakes on all wheels. Any sort of unusual situation can be tackled with such braking system with losing control over the car. If you find this article helpful in choosing the right braking system, tell us know in the comments section below.


Ahmad Shehryar

Electrical engineer. Passionate about cars. Photographer.

Notable Replies

  1. PW bloggers have lost their minds.

  2. Sir, would you kindly elaborate a bit, the wrong in this blog?

  3. In english it perfectly fits the saying of "preaching to the choir"

    now furthermore, the blog only speaks of disc brakes in passenger cars, but the title doesnt. HD vehicles (trucks) and buses use drums, yet stop perfectly fine.

    its 2018, disc brakes have been installed on cars for a long time now, even a loaf of bread knows what a disc and drum are and how they act.

  4. Bhai pakweels itself has lost it's charm.....or we have grown up too much.....everybody just ask which oil to use blah blah.....no technical discussion here nowadays

  5. Pakistani awaam loves oil.

    No matter if they drive a piece of trash

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