How do ABS Brakes Actually Work?

With over 27 years in the automotive industry and nearly a decade in automotive talk radio, Tom Torbjornsen makes learning about cars easy with his personal manner, his expert advice, and his high energy and entertaining style. Tom has the unique gift of simplifying the complex and tearing down the technical, meeting you at your level of understanding. You will be encouraged as you gain the confidence to deal with problems related to the second most expensive purchase you will make in a lifetime - your automobile.

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Posted Mar 31st 2008 3:37PM by Chris
Filed under: Car Safety

ABS (Anti-Lock Braking System) uses wheel speed sensors, a hydraulic control unit, and a computerized electronic control module, which is the "brain" of the system. When the brake pedal is applied, the electronic control module monitors the speed of the wheels through the wheel speed sensors. If the control module detects that one or more wheels are about to lock up, the module signals the hydraulic unit to control hydraulic pressure to that wheel or wheels. This varying of pressure is much like "pumping" the brake; only with the ABS system, the wheel that is locking up (causing a potential loss of control) is the only one being controlled, while the rest of the wheels are free to roll. This maximizes vehicle steerability.

Tags: ABS, car brakes, car repair, CarBrakes

Reader Comments (Page 1 of 1)

1. How do I post a question, I have a 1993 Chevy 1500 that will not start it turns over but will not start, I have changed out plugs, wires, distributor cap and rotary button, gas filter and fuel pump I am stumped I usually keep it at half full of gas I decided to fill it because gas had gone down a bit I drove from one end of town to the other and parked it at home when I went to drive again it would not and has not started since HELP!

Posted at 10:24PM on Aug 10th 2008 by bkbenn67

2. I too need to know how to post a question. Can anyone help me. My daughters 2001 mitsubishi eclipse brakes are continuing to lock up and the car just stops. She could be killed or injured. This started when garage put on new brakes but all they could do was disconnect the ABS relay and it stopped. I took it to another garage that works on imports and they thought they fixed it (1200.00 later) with new brake lines, etc., and reconnected the abs relay (the car does not pass inspection with relay disconnected). The car just locked up again and it is in a field. I have to wait 2-3 hours to cool down to drive. The left front wheel was too hot to touch and the pads were cherry red. Does anyone have any helpful solutions before I spend another 1000.00 for ineffective repairs. The car has had to be towed several times.

Posted at 9:39PM on Nov 11th 2008 by don falcone

3. iam trying to find infromation on the brake system for a 1994 olds cutless cerria

Posted at 5:18AM on Nov 23rd 2008 by gerald w roat

4. the 2001 mitsubishi more than likely has a bad flex brake line from the chassie to the wheel hub brake. a bit of lose liner from wear is acting like a check valve and holding the brake fluid from returning back to the master cylinder when the brake is released. change your flex hoses.

Posted at 4:25PM on Nov 25th 2008 by Douglas W. Jones

5. I have a brake system problem on an 2004 expedition.
While driving down the road the brakes apply themselves. They do not want to release. It has done this several times and they may release in 10 minutes or 2 hours. Once they release it may be a week or up to a month before this happens again. The ABS light has never come on and the pads and rotors are fine. The brake level is normal. What is causing the brakes to apply by themselves? Any info or advice would be appreciated. Thanks!

Posted at 8:57AM on Dec 27th 2008 by jcmcdaniel

6. 2000 PONTIAC MONTANA,(ABS) "ANTI-LOCK BRAKES", (TCSR)"TRACTION CONTROL SERVICE REQUIRED" LIGHT AND "TRAC OFF" LIGHT, ARE ON WHEN COLD. I am new and dont know how to search for past blogs related to this subject, if you can help please do. My problem is that my "ABS" light, "TCSR" light, and "trac off" light all three come on when the van is cold and ambient temps are below 17 degrees f. The "TCSR" light goes off after 1-2 minuites. The "ABS" and the "TRAC OFF" lights only go off after you turn off and turn back on the ignition after the van has warmed up (10-15 min.) At no time do the brackes ever feel funny or fail to work under normal stopping use.

Posted at 11:11AM on Dec 22nd 2008 by brian

7. Stopping a car in a hurry on a slippery road can be very challenging. Anti-lock braking systems (ABS) take a lot of the challenge out of this sometimes nerve-wracking event. In fact, on slippery surfaces, even professional drivers can't stop as quickly without ABS as an average driver can with ABS. http://www.chiefenterprises.com

Posted at 1:09PM on Jan 29th 2009 by Bosch Relay

8. Stopping on wet pavement will increase the distance that you need in order to stop. This is one of the main applications that ABS breaks are used for. Another Safety issue is to have the cracks in your windshield either repaired or replaced.

http://www.windshieldreplacementphoenix.net

http://www.windshieldreplacementaz.com

http://www.rvwindshieldreplacement.net

Posted at 5:31PM on Mar 12th 2009 by WindshieldGuy

9. I have a 2002 escalade ext with 30,000 miles on it. The pads went bad from sitting. I replaced the pads all around lubed cleaned. now some times you can feel the abs come on. I assume a sensor is bad any ideas

Posted at 10:13AM on Apr 16th 2009 by KwDowney

10. I have a 2002 Toyota Camry with 36000 miles. My brake pedal is soft and sometimes feels hard when I stop. I had the pads looked at and they were OK. I was told to listen for a hissing noise to see if booster was good. No hiss. Can you advise me of what might be the problem? Thank you

Posted at 3:38PM on Jun 16th 2009 by thomas miller

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