Power Brakes - How do they Function?

Power assisted brakes (also known as power brakes) are brake systems designed with the intent of using lesser force to initiate a stronger braking power. Back in the day, when most cars had drum brakes, power brakes were not really necessary -- drum brakes naturally provide some of their own power assist. Since most cars today have disc brakes, at least on the front wheels, power brakes have become indispensable. Without this device, a lot of drivers would have very tired legs. How do they function?



In their designed, power brakes uses either the power of the engine and/or battery to enhance your braking power. Whilst you can generate a fair amount of force using your foot, power brakes uses systems from elsewhere in the car to help you apply even more force means that you get more powerful brakes as a result.

If you're curious about how power brakes work, go out to your car and with the engine off, step on the brakes. They'll have a slightly solid, almost wooden feel to them. Turn the engine on and do it again and you'll notice a lot less back-pressure on the pedal. This is the power assist which is making it easier for you to depress the pedal. 

There are four common types of power brakes. These includes:

• vacuum suspended

• air suspended; 

• hydraulic booster, and 

• electrohydraulic booster. 

The most commonly used in cars however is the vacuum suspended units (vacuum boosters). In this type of system, when you press the brake pedal, the push rod to the master cylinder opens a vacuum control valve. This allows vacuum pressure (normally from the intake manifold) to "suck" on a diaphragm inside the vacuum assist unit. This extra vacuum suction helps you to produce more force at the pedal end of the brake system.

Hydraulic booster systems usually utilize pressure from the power steering system to augment pressure on the master brake cylinder.

Electrohydraulic booster systems use an electric motor to pressurize the hydraulic system downwind of the brake pedal which has the effect of amplifying the internal pressure in the whole system.The advantage to this system is that as long as you have battery power, you have power brakes even if the engine fails. With vacuum-assist brakes, no engine means no assistance.