Anti-Lock Braking System (ABS)
What it is: ABS keeps the wheels from fully locking up while braking to allow the driver to maintain steering control. There are two basic types of ABS. Rear Wheel ABS prevents only rear wheels from locking. Four Wheel ABS prevents all four wheels from locking. Without ABS, too much force applied to the brake pedal can cause a wheel to stop turning (lockup) and begin skidding, greatly reducing the capability of the driver to steer or maintain stability. With ABS, the wheels are kept rolling and the driver maintains steering control within the limits of traction. Many light trucks use rear-wheel ABS to prevent rear wheel lockup. Rear Wheel ABS does not help steering directly during hard braking, but it helps to keep the vehicle stable and reduces fishtailing and a loss of control.
How it works: ABS consists of an electronic control unit (ECU) with a microprocessor, hydraulic control unit (HCU) with valves (to modulate brake line pressure), and wheel speed sensors at each wheel or in the differential. Four Wheel ABS systems also have a pump and motor in the HCU. If a wheel begins to lock up during braking, the computer senses a speed difference compared to the other wheels. The HCU reduces pressure to that brake until it begins to roll again. This occurs many times per second during braking, making pumping of the brakes unnecessary. When the brake pedal is applied firmly, the system constantly seeks to keep each wheel at maximum braking force without locking up to help the driver make the best use of available traction.
Customer benefit: ABS provides the average driver with greater vehicle stability and control during severe braking. Additionally, Four Wheel ABS can help the driver steer away from a potential accident.
Ford status: Available on all cars and light trucks sold in North America.
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