How Hydraulic Brakes Work

In this article we’ll cover the types of hydraulic brakes and how they work. A hydraulic brake is a type of brake in which the friction force is provided by oil pressure, and the oil used in a hydraulic brake is a special mineral oil.

When foot force is applied to the brake pedal, brake hydraulic pressure is generated in the master cylinder. With the applied pressure, it spreads equally through the brake lines and hoses to the wheel brake cylinder, and the hydraulic pressure converts into a clamping force, applying pressure to the brake drums or discs.

Application of Pascal’s Principle

Hydraulic brake systems transmit the force applied to the brake pedal to all wheels with equal pressure, using Pascal’s principle.

Brake Fluid

The hydraulic fluid used in the brake system is specially formulated to have a high boiling point.

Role of the Master Cylinder

The master cylinder is the critical component that converts pedal force into hydraulic pressure and delivers it to the brake lines.

Working Principle of Hydraulic Brakes

There are 2 types of hydraulic brakes.

Hydraulic Drum Brakes
Hydraulic Disc Brakes

How Do Hydraulic Drum Brakes Work?

The brake drums rotate together with the wheels, and inside each drum are brake shoes fitted with brake linings. When the pistons press against the drums, they generate braking force from the inside, which slows the wheel’s motion. Friction converts kinetic energy into thermal energy. It’s also important for a drum brake to have adequate ventilation for heat dissipation.

How Do Hydraulic Disc Brakes Work?

In the hydraulic brake system, the force applied to the brake pedal is compressed via Pascal’s principle, and the motion of the hydraulic fluid is transmitted to the pistons. This causes the pads to rub against the disc, resulting in slowing or stopping. Until recently, discs were commonly used at the front and drum systems at the rear. Now, four-wheel disc brake systems have become widespread.

1- When the driver presses the brake pedal, the master cylinder’s piston moves like a medical syringe, driven along the pushrod.

2- The master cylinder’s brake fluid is then compressed, converting mechanical energy into hydraulic energy.

3- Through the brake lines, the caliper cylinder receives high-pressure brake fluid from the master cylinder.

4- The high-pressure brake fluid is then pushed onto the piston and the brake pad. (The brake pad is attached to the cylinder piston)

5- With this motion of the brake pad, the rotating disc rotor is clamped, and friction contact occurs between the rotating disc rotor and the brake pads. The vehicle’s kinetic energy converts into heat energy, and the vehicle’s speed decreases and it stops.

How the Caliper Assembly Works in Disc Brakes

Related Questions

According to Pascal’s principle, pressure applied to an enclosed fluid is transmitted equally to every point in the fluid. The hydraulic pressure leaving the master cylinder is distributed to all wheels at the same rate through the lines, based on this principle.

A significant amount of heat is generated by friction during braking. If the fluid boils at a low temperature, vapor bubbles form inside it, which prevents brake pressure from being transmitted properly and weakens braking power.