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What is ABS and how does it work?

We can all try to drive as diligently and safely as possible, but occasionally something happens which means an emergency stop is needed to get us out of trouble.

It can be a nerve-wracking event at the best of times, but on a slippery surface things can get even more tricky. In the past, heavy braking in such a situation could result in locking up the car’s wheels. Not only does a locked wheel increase the stopping distance over a freely rotating wheel (marginally in the dry, and often by a significant margin on slippery surfaces) but it also removes the ability to steer out of trouble.

The invention of anti-lock brakes (ABS) has doubtlessly reduced the number of road traffic accidents since it’s first application – as we know it today – to road cars by Chrysler in the early 1970s.

But how does it work?

Before ABS became a widespread invention, drivers used a technique called cadence braking if they needed to bring their car to a stop sharpish. This involves pumping the brake pedal as quickly as possible to lock and unlock the wheels, allowing a degree of steering control while still braking hard.

Modern ABS systems work on a very similar principle. ABS is based on several main components. The car’s ECU (Electronic Control Unit, or computer “brain”) is connected to four speed sensors, one attached to each wheel. When one of those sensors returns a speed reading significantly lower than the others, the system assumes that the slower rotating wheel is about to lock, and reacts by releasing braking force on the affected corner. As the wheel speed returns to a similar level to the others, braking force is then electronically increased again.

On the very best systems, this process of applying and retarding pressure happens as many as fifteen times every second. For anyone unfortunate enough (or fortunate enough, depending on your point of view) to have used the ABS on their car, you’d feel this happening as a fast pulsing through the brake pedal. This system maintains braking force around the point at which the wheels lock, allowing the maximum braking force to be applied without loss of steering control for the driver.

As you can imagine, not even the best drivers in the world can perform cadence braking fifteen times per second, so even an average driver can stop a car equipped with ABS sooner and with greater control than a pro could without it.

Does my car have ABS?

If it was built in the last fifteen years, and isn’t a low volume British sports car like a TVR or Morgan, we practically guarantee that it does. Even many motorcycles use the technology now, too – useful, because locking the front wheel on a motorbike is usually followed rather swiftly by skimming down the road on your backside. Don’t ask us how we know.

It is important to make sure that the ABS warning light on the dash is off during normal driving, otherwise there is a fault with the system, in which case the ABS will not be working when it is needed.

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