All about Drum Brakes

3 min readAug 24, 2020


Braking is the department that may have a limit in its functioning that is ‘To Apply Brakes and stop the vehicle’ but as far as its significance is concerned, it forms yest the most crucial of all.

Let’s take a situation of owning a car that may have the most powerful engine, say a V-12 or W-16 or W-18 configuration, an automatic transmission system with turbocharger/ supercharger equipped and 4-wd or Awd and is capable of attaining top speed within a blink of an eye.

Now with all such classic, unbeatable configurations if the car is not able to be stop then it would automatically be the last ride/drive of the driver and passengers accompanying him.

Therefore, it makes it necessary for the vehicle to be very well equipped with some sort of mechanism/system in order to reduce the car and gradually allowing is to stop without any further complications.

Also, it would rather suggest a car that do not compromise on such types of crucial takes.

Now as we have learnt about why do we need brakes, let us go into a brief understanding on what are brakes and how they function and types of braking system/brakes.

What are Brakes?

Brakes are a mechanical system/mechanism which restricts a certain motion of any object/device and is able to absorb the energy.

What are different types of brakes?

On the basis of power

  • Mechanical Brakes
  • Hydraulic Brakes
  • Air Brakes
  • Vacuum Brakes
  • Power assisted Hydraulic Brakes
  • Mechanical Brakes
  • Electrical Brakes
  • By method of Application
  • Foot Brakes
  • Hand Brakes

Method of operation

  • Manual
  • Servo
  • Power operation

Method of Braking Contact

  • Internal Expanding Brakes
  • External Contracting Brakes

Method of applying brakes force

  • Single Acting Brakes
  • Double Acting Brakes

Let us discuss about Drum Brakes Today:-

DRUM BRAKES ( Internal Expanding or External Contracting Brakes)

Main Components

  • Brake Drum
  • Brake Plate
  • Brake Shoes
  • Brake Liners
  • Retaining Spring
  • Cam
  • Brake Linkages


The Brakes shoes are generally placed inside the brake drum and are generally 2 in numbers.

A cam is placed at the center inside the brake drum that are connected to the both the brake shoes via brake liners.

Now, as the brake pedal is pressed, the mechanical linkage allows the cam to move that in turn is connected to the both brake shoes via brake liners.

This allows the brake shoes to rub against the moving wheel that tries to restrict the motion of rotating wheel by opposing i opposite direction due to friction.

After the speed has come to the desired magnitude, the driver pulls of the pedal from pressing and the mechanism now tries to comeback to its original position and also the brake shoes comes to their original position with the help of the retaining spring.

This is how the cycle continues and thus brakes are constantly applied on to the wheels.

Advantages of Drum Brakes

Drum brakes are able to provide more braking force as compared to same diameter disc brake.

Drum brakes may work longer due to an increased friction contact area than a disc brakes.

Drum brakes are comparatively cheaper and easy to manufacture than the disc brakes.

Drum brakes at the rear side usually generates lower heat.

Drum brakes also have a built-in self energizing effect that requires less input force.

Wheel cylinders are easy to work upon compared to disc brake calipers.

Brake shoes can be manufactured again for future use if needed.

Drums of drum brakes are more resistant to corrosion.

Disadvantages of Drum Brakes

Excessive heating may cause the drum to distort, and thus initiating vibration under braking.

During hard braking the size of drum may increase due to thermal heating and thus driver needs to press further for effectiveness.

Brake shoes can overheat to the point where they become glazed.

Excessive braking mat lead to fluid evaporation.

Relative complexity also adds up to its one disadvantage.

Maintenance of drum brakes in comparison to the disc brakes are more time consuming.

Originally published at on August 24, 2020.




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