ABS BRAKES
Today, most vehicles come from the factory with an antilock braking system, or
ABS. Let’s take a look at its design and function.
ABS uses wheel speed sensors, a hydraulic control unit, and a computerized
electronic control module (the “brain” of the system). When you depress the
brake pedal, 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. However, the wheel that is locking up (causing a potential
loss of control) is the only one being controlled; the rest of the wheels are free to
roll. This individualized control of the brakes maximizes vehicle steer-ability in
a braking situation.
Aside from the addition of these ABS components, the braking system pretty
much remains the same in design and operation. Replacement of friction
materials, such as brake shoes and pads, is the same. When the ABS light is lit
on the dash, the system must be scanned with a hand-held computer. The
computer uses ABS software that interfaces with the ABS data stream to track
down the cause.
A few things you may notice the first time you use antilock
brakes:
- When the pedal is applied and ABS is activated, the pedal may feel harder than
usual. - The pedal may seem to ratchet or pulsate (vibrate), or there could be a
combination of these sensations. - You may hear a noise that sounds like a motorboat engine. This is the
hydraulic control unit operating.
All these traits are normal; no need to worry.Two important things to remember when driving a car with ABS
brakes:
- Maintain the same safe stopping distance as you do with conventional brakes.
ABS will not make the vehicle “stop on a dime;” they simply improve