How Your Anti-Lock Brakes Work

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How Your Anti-Lock Brakes Work

How Your Anti-Lock Brakes WorkYou depend on your brakes to stop your car but do you how your anti-lock brakes work? Here at Dakota Ridge Automotive in Littleton, we provide complete anti-lock brake systems diagnosis and repair, so you can drive safely and not worry if your brakes will work. Today, we’ll get into more detail about this vital system so that you can better understand your vehicle basics and the work we do at the shop.

Brake failure can be a very scary and dangerous situation. If your brakes aren’t working right, you’re at risk of losing control of your vehicle, having a potentially serious accident. Brake-related problems are usually preventable with regular checks and timely brake repairs from our experts at Dakota Ridge Auto.

Here’s how your car’s anti-lock braking system (ABS) works. A skidding wheel has less traction than a non-skidding wheel. Anti-lock brakes were designed to keep wheels from skidding while the car slows down. This allows you to stop faster and more easily steer the vehicle until you get it stopped safely. In particular, your car’s anti-lock braking system (ABS) can save your life on a wet road. Anti-lock brakes stop the wheels from locking up and provide the shortest stopping distance on slippery surfaces.

Let’s take a look at how your anti-lock brakes work by explaining the four main components of an ABS system: the speed sensors, the pump, the valves and the controller.

The Speed Sensors

Located at each wheel, or in the differential, this component detects when the wheel is about to lock up.


Each brake controlled by the ABS has a valve. Many systems have a three-positions value. The first is when the valve is open and pressure from the master cylinder passes right through to the brake. In the second position the valve blocks the line that isolates the brake from the master cylinder, so the pressure doesn’t rise any further if the driver pushes the brake pedal harder. The third position allows the valve to release some of the pressure from the brake.


When the valves release pressure from the brakes, the pump gets the pressure back up.


The controller is a computer that watches the speed sensors and controls the valves.

Here’s how your anti-lock brakes work when all these parts work together. The controller constantly monitors the speed sensors. It checks for decelerations in the wheel that are not usual. Immediately before a wheel locks up, there will be a rapid deceleration. This is because the wheel stops faster than the car. Here’s an example, a car might take five seconds to stop from 60 mph under good conditions, but if a wheel locks up it could stop spinning in less than a second. That’s a big problem.

The anti-lock brake system controller adjusts for the fact that it can’t decelerate so rapidly. It reduces the pressure of the brake until it senses acceleration, then it increases the pressure until it senses the next deceleration. This is done very quickly, even before the tire can actually significantly change speed. So with ABS, the tire slows down at the same times as the car, and the brakes keep the tires from locking up. This offers the maximum braking power.

In this type of driving situation, you will feel a pulsing in the brake pedal, which comes from the rapid opening and closing of the valves. Some ABS systems can cycle up to 15 times per second. This is your car doing its job, so don’t let up or pump your brakes.

Anti-Lock Brake Types

ABS systems have variations and control algorithms depending on the type of brakes. They are referred to by the number of channels (how many valves are individually controlled) and speed sensors.

  • Four-channel, four-sensor ABS

This system works the best because there is a speed sensor on all four wheels and a separate valve for all the wheels. The controller keeps track of every wheel, making sure it is achieving maximum braking force.

  • Three-channel, three-sensor ABS

This system is often found on pickup trucks with four-wheel ABS and has both a speed sensor and a valve for each of the front wheels. It also has a valve and a sensor for the rear wheels. The speed sensor is on the rear axle for the rear wheels.

This system gives individual control of the front wheels, offering both maximum braking force. The rear wheels are monitored together. So, in the rear, they both have to start to lock up before the ABS will activate. Sometimes one of the rear wheels will lock up during a stop, which reduces the braking effectiveness.

  • One-channel, one-sensor ABS

This system is usually seen on pickup trucks with rear-wheel ABS. It has one valve, which controls both rear wheels. It has a one-speed sensor, which is located in the rear axle. It works the same as the rear end of a three-channel system. The rear wheels are monitored together and must both begin to lock up before the ABS takes control. One of the rear wheels sometimes will lock, which reduces the braking effectiveness.

Again, you should not try and pump the brake pedal when stopping in slippery conditions if you have anti-lock brakes because pumping the brakes will just interfere with your braking and take longer to stop. With an anti-lock system, you should press the brake pedal firmly and hold it down, while the ABS does what it’s supposed to do. You will feel the pulsing in the pedal but that’s okay. Don’t let your foot off the brake until you stop.

Now that you know how your anti-lock brakes work, come on in and let us do a brake check. Our auto technicians at Dakota Ridge Automotive in Littleton will make sure your brakes are working when you need them. If your brakes are failing, we will replace them, and get you back on the road knowing you can stop when you need to, so you and your passengers will be safe.

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