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What Is A Power Brake Booster And What Does It Do?

The brake booster is a device used to amplify the force applied on the brake pedal when transferring that force to the brake master cylinder. Brake systems that have them are often called “power brakes.”

The brake booster is used on almost all cars with hydraulic brakes — you won’t see them on vehicles that use pressurized air systems as their primary brake circuits.

Here’s how the brake booster is a vital part of your brake system:

Your foot applies around 70lbs of force to the brake pedal when you press it.

That force goes through the brake booster, which amplifies it (often adding 200-300 lb of force) on the master cylinder

The master cylinder then converts that force to hydraulic pressure

The hydraulic brake fluid transmits that pressure through the brake lines

The transmitted hydraulic pressure engages the brake caliper (in a disc brake) or the wheel cylinder (in a drum brake)

The brake pads (on a brake caliper) or brake shoes (on a wheel cylinder) then use this pressure to generate friction and slow the wheels to a stop

What if modern cars didn’t have a booster?

Without a brake booster, we’d have to press down a lot harder than we usually do to get the brake system to engage. Stopping distances would increase, and emergency braking probably wouldn’t be as effective!

What else are brake boosters known as?

Since brake boosters have been around for a while, they have other names like:

Power brake booster

ower brakes system

Brake vacuum servo

Brake power booster

Vacuum booster

There are three types of brake boosters.

Each brake booster is typically mounted on the firewall in the engine compartment. You’ll find it attached between the brake pedal and the master cylinder:

1. Vacuum Brake Booster

The vacuum brake booster is the most commonly used type.

It utilizes the engine vacuum in naturally-aspirated petrol engines to amplify the pressure applied on the brake pedal.

2. Vacuum Pump

Some road vehicles use a vacuum pump instead of the engine intake manifold.

These include:

Cars with turbo-charged engines

Vehicles with diesel engines

Electric vehicles

Hybrid vehicles

Vacuum pumps can be driven mechanically (from the engine) or via an electric motor (electric brake booster). The vacuum pump is also used in high altitude locations where naturally-aspirated vehicles can’t produce enough vacuum for the brake booster.

3. Hydraulic Brake Boosters

This type of brake booster uses direct hydraulic pressure generated by the power steering pump instead of relying on vacuum pressure.

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