Skip the auto shop - Our mechanics make house calls

How Anti-Lock Brakes Work

How Anti-Lock Brakes Work

An anti-lock brake system (ABS) is a braking system that is made to allow a vehicle to maintain traction with the road when braking. Braking is controlled by driver input via the brake pedal, and older braking systems response to a driver braking suddenly or with intense pressure was sometimes to lock up or skid. The ABS is meant to prevent the wheels from locking up or from unnecessary skidding while braking. The automated system uses the principles of both cadence and threshold braking, which were previously practiced by skilled drivers with early generation braking systems. Modern ABS accomplishes these principles with better control and much faster than a driver could.

Today's anti-lock braking system gives the driver better vehicle control and reduces stopping distances on slippery and dry surfaces. However, on loose gravel and snow, anti-lock brakes can increase stopping distance, though the improved vehicle control remains the same.

Components of the ABS

  • Speed sensors: Speed sensors are also called wheel sensors or wheel speed sensors. This part uses a magnet and a wire to generate a signal that is sent to the sensor.

  • Valves: Each brake controlled by the ABS has a brake line and a valve. The valve has three positions, controlling the amount of pressure exerted on each brake, to minimize wheel lock or skidding.

  • Pump: This piece of the system is used to restore pressure to the brakes after the valve has released the pressure. As the pressure applied by the driver decreases, the pump will help to equalize the pressure in the brake lines.

  • Controller: An Electronic Control Unit (ECU) receives the information from the wheel speed sensor and uses that information to perform the task of applying the brakes with the proper amount of pressure needed.   

These pieces work together to keep proper pressure in the brake lines to help stop a vehicle from skidding or experiencing wheel lock when trying to stop suddenly or in bad weather.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.


Post a question and get free advice from our certified mechanics.


More related articles

Symptoms of a Bad or Failing Flexible Clutch Hose
Common signs include difficulty shifting, low clutch fluid, and feeling no resistance at the clutch pedal.
How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...

Related questions

Q: How do you adjust the Head Restraints?

Your car has five adjustable Head Restraints – one for each of the front seats, and three located on the rear seatback. You can move them up or down to accommodate different heights. Here’s how to do that: Make...

Q: Is It Unsafe to Continue Driving a Vehicle with Broken Wheel Speed Sensors?

The wheel speed sensors are the vehicle’s sensors which are used to collect data for the vehicle’s safety systems. These systems include such safety features as the anti-lock braking system (ABS) and the electronic stability control system (ESC), and both...

Q: no brake pedal

Hello. If there is not any air left in the system then you may have a faulty brake master cylinder. Many times a master cylinder will fail during a brake bleeding procedure as the piston in the master cylinder...