What is it?
ABS is an abbreviation for Anti-lock Braking System. It was designed to help the driver maintain some steering ability and avoid skidding while braking.
ABS was introduced in the mid -1980s and has become "standard" equipment on the majority of vehicles sold in Canada. ABS in cars and most Multi-purpose Vehicles (MPV's) works on all four wheels. This promotes directional stability and allows steering while maximizing braking.
The ABS in most pick-up trucks works only on the rear wheels, which promotes directional stability only. However, there are some available with ABS on all four wheels. Control under heavy braking ABS allows you to maintain control of the vehicle. Since four-wheel ABS prevents all wheels from skidding, it allows you to steer the vehicle and still maintain braking.
How does it work?
ABS uses wheel speed sensors to determine if one or more wheels are trying to lock up during braking. If a wheel tries to lock up, a series of hydraulic valves limit or reduce the braking on that wheel. This prevents skidding and allows you to maintain steering control.
Why do I want or need this?
In a recent Canadian Automobile Association survey of some 1700 members, 66% correctly associated ABS with vehicle stability in an emergency, and 53% correctly stated that ABS allows the driver to steer while braking.
Since the ABS will not allow the tire to stop rotating, you can brake and steer at the same time. The braking and steering ability of the vehicle is limited by the amount of traction the tire can generate.
If you demand steering while braking, the 100% of traction that the tire can generate will be divided between both tasks. For example, if you require 50% for steering then there is 50% of available traction left for braking. If you require 10% for steering then there is 90% left for braking. Be aware that 100% traction on a dry road is a great deal more traction than 100% traction on ice! Therefore, your vehicle is unable to steer and brake as well on a slippery surface as it can on a dry road.
How do I use ABS?
Apply steady and constant pressure - do not take your foot off the brake pedal until the vehicle has stopped and do not pump the brake.
What is that noise and vibration?
This is normal and indicates that the ABS is active. Various ABS sound or feel differently. Some of the effects, for example are:
- a groaning noise
- a rapid pulsing of the brake pedal
- a periodic dropping of the brake pedal
- a hard (non compliant) brake pedal
- a light that turns on to say "low traction".
You should familiarize yourself with how your system functions by first reading the "Owner's Manual" and then testing your ABS in an empty parking lot under various climatic conditions i.e. dry, wet, snow and ice.
Brake pedal will pulsate: As the ABS engages, you may feel the brake pedal pulsating. This is caused by the system applying and releasing pressure to the brakes.
The noise associated with ABS when it is functioning should not be confused with brake squeal. If your brakes squeal under normal braking, this may mean the brake pads are worn and need replacing. A pulsing brake pedal every time you apply the brakes may mean warped brake rotors and/or seized brake calipers that require servicing.
REMEMBER...WHEN IN DOUBT, CHECK IT OUT. Transport Canada recommends that if you are experiencing any abnormal braking, have it checked out at your dealer.
Is the stopping distance shorter with ABS?
No! From early commercials, it may have looked like you could stop on a dime. That instantaneous stop is not realistic. When braking on dry or wet roads your stopping distance will be about the same as with conventional brakes.
You should allow for a longer stopping distance with ABS than for conventional brakes when driving on gravel, slush, and snow. This is because the rotating tire will stay on top of this low traction road surface covering, and effectively "float" on this boundary layer.
A non ABS braked vehicle can lock its tires and create a snow plow effect in front of the tires which helps slow the vehicle. These locked tires can often find more traction below this boundary layer.
Snow Tires!
Braking and steering are limited by the amount of traction your tires can generate. Testing has shown that good snow tires reduce the stopping distance of an ABS equipped vehicle in winter conditions.
Rather than installing only two snow tires on the drive wheels, it is RECOMMENDED that you install four snow tires to maintain equal traction on each wheel. This will help you to steer, stop, and accelerate.
ABS warnings!
My ABS light comes on. What should I do?
When you start your vehicle an ABS indicator light will illuminate on the instrument panel for a few seconds. This is normal.
My ABS light stays on. What should I do?
This means the ABS is not working. However, the conventional braking system is working. We recommend that you take your vehicle to your
nearest dealer for servicing as soon as possible.
My ABS light and my brake warning light both stay on. What should I do?
DO NOT DRIVE THIS VEHICLE! You have no brakes. Have it towed to your nearest dealer.
Maintenance problems with ABS
It is possible for the ABS to be too sensitive and that it activates for no apparent reason. For example, if the ABS activates when gently braking on a smooth, dry surface, you should visit your dealer.
Road surfaces and ABS
Road hazards that will cause the ABS to function unexpectedly are gravel, sand, ice, snow, mud, railway tracks, potholes, manhole covers, and even road markings when it is raining.
The ABS cannot make up for road conditions or bad judgment. It is still the driver's responsibility to drive at reasonable speeds for weather and traffic conditions. Always leave a margin of safety.
Does Transport Canada have a safety standard for ABS?
No, not for ABS alone. Transport Canada does have a standard for effectiveness of a vehicle's intact brake system, which includes braking performance in case of a failure of part of the system.
Do all ABS-equipped vehicles brake in the same way?
No. Some ABS equipped vehicles perform differently than others, which is why it is important to learn the braking characteristics of your vehicle.
How can I become familiar with my vehicle's ABS?
Find yourself an empty parking lot with lots of room to maneuver. Practice hard braking stops from 30 km/h in this safe location. Note the brake pedal feel, sound and vehicle control during braking in a turn or in a straight line. Remember, ABS will perform differently depending on the road surface or weather conditions.
Should I disconnect my ABS?
No. ABS provides the average driver with above average vehicle control in most conditions.
If I have a concern about my ABS, whom should I contact?
Contact your dealer first and have the ABS and basic brake system checked.
