instrument cluster BMW CONVERTIBLE 1998 User Guide

10 3
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ABS enhances active safety by helping
to prevent the wheels from locking under
braking. 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
uncontrolled oversteer.
ABS is designed to meet two essential
requirements during every application:
dto help provide vehicle stability on all
types of road surface (asphalt,
cement, dirt, moisture, snow and ice).
dto help to retain steering and maneu-
vering capability under the same con-
ditions.
However, certain important consider-
ations must be borne in mind in connec-
tion with these requirements:
Not even ABS can suspend the normal
laws of physics. ABS alone can not pre-
vent accidents when the brakes are
applied without an adequate safety
interval between vehicles, when the car
reaches excessive rates of lateral accel-
eration in curves, or if aquaplaning
occurs. Responsibility for these types of
situations remains in the hands (and 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 that could
affect your own safety and that of others.
Driving with ABSThe yellow ABS warning in the instru-
ment panel goes out as soon as the
engine is started.
The system becomes operative once the
vehicle exceeds a speed of 5 mph
(8 km/h). The ABS is deactivated when-
ever the vehicle's speed drops below
approx. 2 mph (3 km/h). This means that
the wheels can lock in the Þnal phase of
a braking action - a factor of no signiÞ-
cance in actual practice.
The ABS system closed-loop control cir-
cuit cycles in fractions of a second. A
pulsation at the brake pedal indicates to
the driver that ABS is active, that is, that
the car is within its maximum braking
range. In addition, the audible pulsation
that accompanies the control operation
calls your attention to the reduced trac-
tion between tires and road surface
(marginal adhesion), and reminds you
that the vehicle's speed should be
reduced to adapt to road conditions.On road surfaces featuring a loose top
layer on a Þrmer substratum, e.g., on
gravel or snow, the braking distances
with ABS may be longer than with the
wheels locked. However, ABS continues
to provide enhanced vehicle and steer-
ing control under these conditions.
a
To ensure that the system remains
completely operational, never modify the
ABS. Service procedures on ABS are to
be performed by authorized technicians
only.c
ABS may fail to function with maximum
efÞciency when tires of different sizes
are mounted (e.g., winter tires/spare tire;
remount the correct tires at all wheels as
soon as possible).
In the event of a fault, the ABS warning
lamp in the instrument cluster lights up,
refer to page 18. The braking system
then reverts to conventional operation as
on a vehicle without ABS. However,
have the brake system checked by your
BMW Retailer as soon as possible. To
prevent undetected defects and cumu-
lative faults from adversely affecting the
brake system, refer any problems to
your authorized BMW Retailer at the
earliest opportunity.
Antilock Brake System (ABS)