BMW 2001 325CI, Manual

Page: 122 / 215

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Antilock Brake System (ABS)
The concept
ABS enhances active safety by helping
to prevent the wheels from locking
under braking. This is because locked
wheels are dangerous. When the front
wheels slide, the driver loses steering
control over the vehicle. Traction loss at
the rear wheels can cause the rear end
to break into an uncontrolled skid.
The system can achieve the shortest
braking distances possible under most
conditions (on straight-aways and in
curves, on asphalt, ice, wet road
surfaces, etc.).
ABS is designed to meet two essential
requirements during every brake appli-
cation:
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To help provide vehicle stability.
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To help maintain steering control and
maneuverability – on all types of road
surfaces (asphalt, concrete, mud, wet
road surfaces, snow, ice).
Braking with ABS
At about 6 mph (10 km/h), the system
becomes operative. Whenever the
vehicle's speed drops below approx.
4 mph (6 km/h), the ABS is deactivated.
This means that the wheels can lock in
the final phase of a panic stop – a factor
of no significance in actual use.
If you are in a situation that requires full
braking, you will exploit the full benefits
of the ABS system if you apply maxi-
mum brake pressure ("panic stop").
Since the vehicle maintains steering
responsiveness, you can nevertheless
avoid possible obstacles with a
minimum of steering effort.
The ABS system closed-loop control
circuit cycles in fractions of a second.
A pulsation at the brake pedal, together
with the sounds associated with the
hydraulic controls, tells you that the
brake system is within its maximum
limit range and reminds you that you
should adapt road speed to the road
conditions.
On road surfaces that have a loose
surface layer on a firm base with good
traction (on gravel or snow, for
example), or when snow chains are
mounted, braking distances may be
longer than with locked wheels.
Nevertheless, ABS possesses the
advantage of vehicle stability and
steering response.
Information for your safety
Not even ABS can suspend the laws of
physics. ABS cannot prevent the
consequences of brake applications
with inadequate clearances for safety
between vehicles, when exceeding the
speed limit, or the risks involved when
aquaplaning occurs. Responsibility for
these types of situations remains in the
hands (and at the feet) of the driver. You
should never allow the added safety of
ABS to lull you into a false sense of
security, or mislead you into taking
increased risks.
Do not make any modifications to
the ABS system.
Service procedures on ABS are to be
performed by authorized technicians
only.
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