Anti-lock Braking System (ABS)

The primary purpose of anti-lock brakes is to help the driver brake and steer the car under a hard braking situation.

Hit the brake pedal all the way to the floor while cruising along at highway speeds for an emergency, the wheels lock up (which means they stop rotating but start skidding), you have no control over the steering of the car. The car then slides along on its locked wheels and goes and hits precisely what you were trying to avoid by braking, which is in front of you. That is what happens when you do not have anti-lock brakes.

When your car does have anti-lock brakes, under the same circumstances hit the brakes and the wheels do not lock up but the car slows down rapidly. You still have control over the steering and therefore can steer the car in which ever direction you want, avoid whatever is in your way and come to a safe halt. That is anti-lock brakes for you.

The basic rules for using ABS are as follows:

1. Stomp – Firmly depress the brake pedal
2. Stay – On the brakes. Do not pump the brakes.
3. Steer – Where you want to go.

ABS is controlled via the onboard computer in your car.

The 4 main components critical to ABS are

1. Speed Sensors - The onboard computer senses via speed sensors. This helps the computer to know which of the wheels are about to lock up and start skidding.
2. Valves - There is a valve in each brake line controlled by ABS. In most systems the valve has three positions;

• Open- When the valve is open pressure from the master cylinder is passed right through to the brake.
• Block – The valve blocks the brake line and prevents the brake pressure rising further to prevent the wheel from locking up.
• Release – The valve releases some of the pressure from the brake as per the speed of the wheel.

3. Pump: When a valve reduces pressure in a brake line the pump is there to get the pressure back up from the brake line.
4. Controller: The onboard computer in the car that manages the whole anti-lock braking system.

In essence what ABS does is massage the brakes on your car at the required pressure (according to the speed at which the vehicle is travelling in), this helps the car not to lock up the wheels thereby retaining the ability to steer and stop your car at the same time.

Most developed nations have made it mandatory for cars to be sold with ABS.