Understanding Your Car’s Anti-Lock Braking System

October 16, 2014 / by / 0 Comment

Stopping a car in a hurry on a slippery road can be very challenging. Before there were Anti-lock Braking Systems (ABS) drivers were told to gently pump their brakes if they felt a wheel lock up when attempting to stop on a slippery road. Today, Anti-lock Braking Systems do this for us. In this article, we’ll learn all about anti-lock braking systems – how they work, what’s in them, and what to do when a tire starts to skid.

How they work:

The theory behind anti-lock brakes is simple. A skidding wheel has less traction than a non-skidding wheel. If you have ever been stuck on ice, then you know that when your wheels are spinning you have no traction at all. The only thing to do is slow the engine down and let the tires “grab”.  ABS systems do the same thing, they sense when a wheel is locking up during braking and they pulse the brake to regain traction.  This allows you to be able to stop faster and you’ll be able to steer your vehicle while stopping also.

The four main components to an ABS system:

Speed Sensors – The anti-lock braking system needs some way of knowing when a wheel is about to lock up. The speed sensors, which are located at each wheel provide this information.

Brake Line Valves – There is a valve in the brake line of each brake controlled by the ABS. This valve controls the brake pressure going to each brake assembly.

Pump – When a Brake Line Valve reduces the pressure in a brake line, the pump is there to get the pressure back up.

Controller – The controller is a computer. It watches the speed sensors and controls the system.
Your ABS at work:

The ABS Controller is the brain of the system.  It monitors the speed sensors at all times and is looking for decelerations in any wheels that are out of the ordinary.  Just before a wheel locks up, it will experience a rapid deceleration. The ABS controller knows that such a rapid deceleration is “impossible”, so it reduces the brake line pressure to that brake until it sees it speed up again. It can do this very quickly, before the wheel can actually significantly change speed. The result is that the tire slows down at the same rate as the car, with the brakes keeping the tires very near the point at which they will start to lock up. This gives the system maximum braking power. When the ABS system is in operation you will feel a pulsing in the brake pedal; this comes from the rapid opening and closing of the valves.

So, what do I do when my car starts to skid?

First, do not pump your brakes.  The ABS system does this for you!  In an emergency stop in a car with ABS, you should apply the brake pedal firmly and hold it while the ABS does all the work. You will feel a pulsing in the pedal that may be quite noticeable, but this is normal so don’t let off the brake.  When your ABS system is functioning properly you should have some steering control back, so use that to get back on course.

Source: Gin Chevrolet


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