What are the disadvantages for hydraulic brakes

Working Of Hydraulic Brakes- Advantages and Disadvantages


The brakes which are actuated by the hydraulic pressure (pressure of a fluid) are called hydraulic brakes. Hydraulic brakes are commonly used in the automobiles. Principle Hydraulic brakes work on the principle of Pascal’s law which states that “pressure at a point in a fluid is equal in all directions in space”. According to this law when pressure is applied on a fluid it travels equally in all directions so that uniform braking action is applied on all four wheels.

Read more: Introduction To Brakes and Different Types Of Brake

Construction and Working of Hydraulic Brakes 

When brake pedal in pressed, the force is transmitted to the brake shoes through a liquid (link). The pedal force is multiplied and transmitted to all brake shoes by a force transmission system. Figure shows the system of hydraulic brake of a four wheeler automobile. It consists of a master cylinder, four wheel cylinders and pipes carrying a brake fluid from master cylinder to wheel cylinder.

The most common arrangement of hydraulic brakes for passenger vehicles, motorcycles, scooters, and mopeds, consists of the following:

a)      Brake pedal or lever

b)      A push rod (also called an actuating rod)

c)      A master cylinder assembly containing a piston assembly (made up of either one or two pistons, a return spring, a series of gaskets/ O-rings and a fluid reservoir)

d)     Reinforced hydraulic lines

e)      Brake caliper assembly usually consisting of one or two hollow aluminum or chrome-plated steel pistons (called caliper pistons), a set of thermally conductive brake pads and a rotor (also called a brake disc) or drum attached to an axle.

The master cylinder is connected to all the four-wheel cylinders by tubing or piping. All cylinders and tubes are fitted with a fluid which acts as a link to transmit pedal force from master cylinder to wheel cylinders. Brake Fluid The fluid filled in the hydraulic brake system is known as brake fluid. It is a mixture of glycerine and alcohol or caster oil and some additives. Master cylinder consists of a piston which is connected to peal through connecting rod. The wheel cylinder consists of two pistons between which fluid is filled. Each wheel brake consists of a cylinder brake drum. This drum is mounted on the inner side of wheel. The drum revolves with the wheel. Two brake shoes which are mounted inside the drum remain stationary. Heat and wear resistant brake linings are fitted on the surface of the brake shoes. 

Application of Brakes 

When brake pedal is pressed to apply the brakes, the piston in the master cylinder forces the brake fluid. This increases the pressure of fluid. This pressure is transmitted in all the pipes and upto all wheel cylinders according to Pascal’s law. This increased pressure forces out the two pistons in the wheel cylinders. These pistons are connected to brake shoes. So, the brake shoes expand out against brake drums. Due to friction between brake linings and drum, wheels slow down and brakes are applied



(a) Equal braking action on all wheels.

(b) Increased braking force.

(c) Simple in construction.

(d) Low wear rate of brake linings.

(e) Flexibility of brake linings.

(f) Increased mechanical advantage.


(a) Whole braking system fails due to leakage of fluid from brake linings.

(b) Presence of air inside the tubings ruins the whole system

See Also: Working Of Pneumatic /Air Braking System