Tech-Talk – What is ABS (Anti-lock Braking System)?

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There are common misconceptions as to what ABS is and isn't, and what it does and doesn't do. TCR Tech-Talk explains.
There are common misconceptions as to what ABS is and isn’t, and what it does and doesn’t do. TCR Tech-Talk explains.

ABS is a phrase not altogether uncommon in the motoring world – almost every new car available on the market boasts these 3 letters on their list of safety features, unless we’re talking about the new Datsun GO among a few others.  As you may know, ABS stands for ‘Anti-lock Braking System’ – but there are many common misconceptions as to what ABS is and does – so right here, let’s clear it all up for you…

ABS does not:

  • Aid the driver in applying maximum braking force. (See EBA below)
  • Apply varying amounts of braking force to different wheels.  (See EBD below)
  • Despite common belief, ABS does not directly reduce the braking distance of a vehicle.

What does ABS do then?

ABS serves the sole purpose of allowing the driver to steer the vehicle whilst under heavy braking, thus allowing them to slow down and swerve around an obstacle, as opposed to merely slowing down and crashing straight into the obstacle.

 

Why do we need ABS to turn while braking?

 

The steering system of a vehicle operates by changing the direction of a rotating wheel.  When the front (steering) wheels of a vehicle lock up (i.e. under heavy braking), they begin to slide.  When this occurs, no amount of turning the steering wheel will affect the vehicle’s direction as it will be sliding in the direction of travel prior to the wheel lock-up.

The only way to regain the ability to turn will be to restart the rotation of the steering wheels.  ABS prevents wheel lockups in braking scenarios, allowing the driver to control the vehicle even under emergency braking by steering out of the way of an impending obstacle.

 

How does ABS work?

Anti-lock braking system is a means of preventing the wheels locking up under braking – as the name would suggest.  It does so using sensors that detect the moment any of the wheels locks up, and temporarily releases the brakes, allowing the wheel to continue rotating before the brakes are re-applied.

How do I know ABS is working?

When braking extremely hard under an emergency situation, you may feel a ‘pumping’ or vibrating sensation on the brake pedal – as if it is pulsating beneath your foot.  You may also hear a knocking sound repetitively.  This is the brake system applying and releasing brake pressure.  Don’t be alarmed, instead stay calm and if need be, turn out of the way of danger – that’s what ABS was meant for after all.

But ABS reduces stopping distances, doesn’t it?

There may be cases when ABS braking does reduce the stopping distance of a vehicle.  By ensuring that the rotation of the car’s wheels slows rather than stopping instantaneously and locking up, a vehicle can slow down more effectively on low-grip surfaces.  This however is a spin-off effect of ABS brakes, and not the main intention/purpose of the system.  It is also unlikely to happen in dry situations, and is more likely to occur during wet weather conditions or on low-grip surfaces.

Related systems to ABS:

Other systems not directly linked, but commonly equipped operating in partnership with ABS, include:

EBA (Emergency Brake Assist) – a system that enhances the braking force applied under emergency braking situations when the drivers reactions or strength are not enough to exert maximum force upon the brake pedal.

EBD (Electronic Brakeforce Distribution) – a system that applies varying amounts of braking force to different wheels in order to slow a vehicle more effectively and keep the vehicle straight under braking.

Conclusion:

ABS is a vital safety system in modern vehicles.  Without it, the ability to avoid accidents under emergency braking situations would be severely compromised.  In combination with EBD, EBA, and other safety systems, ABS has saved many lives on our roads.  But remember, the purpose of ABS is to allow drivers to avoid crashes, rather than stopping before them, by enabling change of direction under heavy braking.

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