Car Advice

What is ABS or Anti-lock Braking System?

11 Oct 2016

Isaac Bober 1

Almost every new car now comes with ABS or Anti-Lock Braking System, but just what is it and how does it work?

ABS, OR ANTI-LOCK BRAKING SYSTEM has been mandated as standard equipment on all new passenger cars for the last decade. But anti-lock brakes aren’t a new thing, rather they’ve been around since the late 1940s, used first on aeroplanes and then adapted for the ground-breaking Jensen FF.

Now, a Google search of the subject will tell you it was Mercedes-Benz that first fitted cars with ABS via a Bosch developed unit (1978), only it was Chrysler that was actually first to the punch with an electronic system in 1971 on the Imperial. Called the Sure-Brake system it was developed by Bendix. Both the Bosch and Bendix systems were electronic (and some only worked on the rear wheels) and according to tests conducted at the time could reduce stopping distances, even on black ice, by 40%.

Why should I care about ABS?

Simple, ABS is designed to keep your wheels from locking up under hard braking. If your wheels lock-up (stop rotating) you’ll lose your steering as your tyres can only ‘steer’ when they’re able to rotate and thus grip the road. And, so, if your tyres have locked up, and you’ve subsequently lost steering you’ll end up as a passenger behind the wheel with only something hard and unyielding to stop your car… like a tree, or another car. So, ABS is important. That said, modern motorists are increasingly overlooking the importance of ABS as ‘poster’ systems become more widespread, like autonomous emergency braking.

Do all cars have ABS?

If you’ve bought a new passenger car in the last decade then, yes, your car will have ABS. But not all ‘cars’ have ABS. For instance, Formula One has ruled against the system being used, because it only wants the best of the best as drivers in the sport. That means a Formula One driver has to not only be able to drive at speeds that would make the rest of us pass out, but also, just as your parents and grandparents had to do in their cars, has to know just how far they can press the brake pedal before the brakes will lock up. It’s one of the lost arts of driving…

How does ABS work?

I remember, when I first started out in this game, going for a passenger ride with a road tester who would jokingly pulse the brake pedal with his fault and giggle that he could pulse the brakes better than ABS. That person was an idiot, but not because he used to pump a car’s brakes, because he was kind of right (an ABS system generally acts around 15 times a second, and there’s no way a human can work that fast). The principle of anti-lock braking is based on cadence braking which old-time racing drivers used to keep the wheels from locking up; they would pump the brake pedal like my idiot colleague suggested. This was then further developed during the 1940s as a mechanical system on aeroplanes and then an electronic system by the likes of Bendix and Bosch.

An Anti-lock Braking System doesn’t actually pulse the brakes. Rather it, while you keep your foot hard on the brakes and your knuckles, and other parts of your anatomy, clenched on the steering wheel releases pressure on the brakes in increments as the system detects lock-up. And the system is able to determine when to intervene via a series of wheel sensors that monitor the wheel’s rotational speed. The sensors are looking for when the wheels have gone from turning quickly to slowly all of a sudden combined with force on the brake pedal.

In a nutshell, ABS will hold the brakes almost to the point of lock up and then releases pressure on them momentarily to allow them to rotate slightly and then it increases pressure again, releases, increases, and so on until you stop.

How will you know if it’s working?

Well, it’s either to tell if it’s not working than when it is… If it’s not working, you’ll generally see an ABS light illuminated on your dashboard. If you’re in a situation when you need to hit the brakes hard enough to activate the ABS you might feel a slight judder through the brake pedal.

Anything else I need to know?

Yes, dirt roads used to play havoc with ABS and stopping distances as a typical road car’s ABS system won’t let the wheels lock enough to dig through the loose dirt on top of the harder stuff beneath. Most SUVs and typically only all-wheel drive variants have their ABS tuned to recognise dirt, some even have a setting, like Volkswagen’s Off-Road button which you should press whenever you’re driving on dirt, which allow the wheels to lock a little more, enough to create a wedge of dirt in front of the tyre, helping it to slow quicker.