Automotive Brakes

ASHWANI KUMAR on 8/23/2021 11:20:51 AM

Automotive brakes are designed to slow and stop a vehicle by transforming kinetic energy (motion energy) into heat energy. As the brake linings contact the drums/rotors they create friction which produces the heat energy. The intensity of the heat is proportional to the vehicle speed, the weight of the vehicle, and the quickness of the stop. Faster speeds, heavier vehicles, and quicker stops equal more heat.


A brake is a mechanical device which inhibits motion.

Pascal's Law

The pressure exerted anywhere in a mass of confined liquid is transmitted undiminished in all directions throughout the liquid.

From this principle, if a master cylinder generates 500 psi, it also transfers 500 psi to the pistons in each wheel cylinder (remember that fluid pressure remains constant).

The following are the most common types of braking systems in modern cars:
  • Hydraulic braking system:
  • Electromagnetic braking system:
  • Servo braking system:
  • Mechanical braking system:
  • Anti-Lock Brakes:

a)Hydraulic braking system:

This system runs on brake fluid, cylinders, and friction. By creating pressure within, glycol ethers or diethylene glycol forces the brake pads to stop the wheels from moving.

• The force generated in the hydraulic braking system is higher when compared to the mechanical braking system.

• The hydraulic braking system considered as one of the important braking systems for modern vehicles.

• The chance of brake failure is very less in case of the hydraulic braking system. 

The direct connection between the actuator and the brake disc or drum makes very less chance of brake failure

b)Electromagnetic braking system:

Electromagnetic braking systems can be found in many modern and hybrid vehicles.  The electromagnetic braking system uses the principle of electromagnetism to achieve frictionless braking. 

This serves to increase the life span and reliability of brakes. Also, traditional braking systems are prone to slipping while this is backed with the quick magnetic brakes. So without friction or need of lubrication, this technology is preferred in hybrids. Also, it is quite modest in size compared to the traditional braking systems. It is mostly used in the trams and trains.

To make electromagnetic brakes work, a magnetic flux when passed in a direction perpendicular to the rotating direction of the wheel,we see rapid current flowing in a direction opposite to the rotation of the wheel. This creates an opposing force to the wheel rotation and it slows down the wheel.

c)Servo braking system:

Also known as vacuum or vacuum-assisted braking. Among this system, the pressure applied to the pedal by the driver is increased.They use the vacuum that is produced in petrol engines by the air intake system in the engine's intake pipe or via a vacuum pump in diesel engines. A brake where power assistance is used to reduce the human effort. In a car, engine vacuum is often used to make a large diaphragm flex and operate the control cylinder.

• Servo braking system boosters used with the hydraulic brake system. The size of the cylinder and the wheels are practically employed. Vacuum boosters increase the braking force.

• Pushing the brake pedal releases the vacuum on the side of the booster. The difference in the air pressure pushes the diaphragm for braking the wheel

d)Mechanical braking system:

The mechanical braking system powers the hand brake or emergency brake. It is the type of braking system in which the brake force applied on the brake pedal is carried to the final brake drum or disc rotor by the various mechanical linkages like cylindrical rods, fulcrums, springs etc. In order to stop the vehicle.Mechanical brakes were used in several old automobile vehicles but they are archaic nowadays due to their less effectiveness.

Types of Mechanical Brakes:


The disc brake is a mechanism for slowing or stopping the rotation of a wheel from its motion. A disc brake is normally made of cast iron, but in some cases, it is also made of composites such as carbon-carbon or ceramic -matrix composites. This is linked to the wheel and/or the axle. To stop the wheel, friction material in the form of brake pads is forced against both sides of the disc. Friction caused, on the disc wheel will slow or stop.


A drum brake is a traditional break in which the friction is caused by a set of shoes or pads that press against a rotating drum-shaped part called a brake drum.

The term \"drum brake\" usually means a brake in which shoes press on the inner surface of the drum. Where the drum is pinched between two shoes, similar to a standard disk brake , it is sometimes called a \"pinch drum brake\", although such brakes are relatively rare.

e)Anti-Lock Brakes:

Anti-lock braking systems (ABS) are found on most newer vehicles. If the stationary brakes are applied suddenly, ABS prevent the wheels from locking up in order to keep the tires from skidding. This feature is especially useful when driving on wet and slippery roads.

Basic components of the brake system

The brake system is composed of the following basic components: the energy-supplying device, the control device, the transmission device,the brake and additional retarder device, brake line (connecting different devices), and ABS (Anti-lock Braking System)

a)The energy-supplying device

The energy-supplying device means supplying and adjusting the necessary energy of braking. According to the types of energy-supplying, there are three types used in automobile braking system:muscular energy braking system (non-power braking system) When we step the brake pedals or the handbrakes, the cars transmit the force from our feet or hands to the brakes. The force from driver supplies the basic energy to brakes. This is non-power braking; it just uses the force from human. 

For example, the bicycle is only using the no-power braking system to supply energy. assisted braking system (power assisted braking system)

The power assisted braking system use the force from drivers and the kinetic energy of engines together.The braking force of power assisted system increases through using the vacuum booster unit. Atmospheric pressure helps to push the brake pedal. Thus, less muscle effort is required.

b)The control device

The main two control devices of braking systems are the service braking system and the parking braking system. They have separate control and transmission devices.The services braking system is foot-operated, while the parking braking system is hand-operated.The service brake acts to slow, stop, or hold the vehicle during normal driving. They are foot-operated by the drivers pressing or releasing the brake pedal. The primary purpose of the brake is to hold the vehicle stationary while it is unattended.The parking brake is mechanically operated, when a separate parking brake foot pedal or hand lever is set.

c)The transmission device

The transmission device is used to transmit the brake energy to brake actuator components. According to different transfer modes, the transmission device includes mechanical braking system, hydraulic braking system and pneumatic braking system

Brake Subsystems

Automotive brake systems can be broken down into several different sub-systems:

• Apply system

• Boost system

• Hydraulic system

• Wheel brakes

• Balance control system

• Warning system


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