Porsche 968 - ABS Brake System; Driving with ABS; ABS Warning Light Indicator

ABS Brake System
(Anti Ill( k l!t tiki' Sy;tem)
AI!.C., tl'pt t•~t·nts a significant improvement in ac-
ltvl' drrvrng ;c~lcty.
It prt•vcnts the wheels from locking during full
hr t~ke application, on almost any road surface,
untrl shortly before the vehicle stops.
ABS ensures:
Full steering control
Good driving stability
Optimum braking
distances
No wheel locking
The vehicle remains
steerable
No skidding due to
locked wheels
Shorter stopping
distances in most
cases
No flat spots on the
tyres
The crucial advantage of ABS is that the vehicle
remains stable and manoeuvrable in hazardous
situations, even when the brakes are applied
fully when cornering.
In spite of this the driver must still take the re-
sponsibility for adjusting his driving actions to
road and weather conditions, and to the trafllc
situation. The increased safety offered by the
system should not induce you to take increased
risks.
Driving with ABS
Sensors measuring wheel rotation are installed
on all four wheels. If a wheel reaches a rota-
tional speed that is too low for the vehicle's
speed, and thus threatens to lock, the control
process begins. Brake pressure is regulated in-
dividually for each front wheel, and for the rear
wheels as pair .
If the road is slippery on one side, the rear
wheel that is braking on the slippery surface
determines the brake pressure for both rear
wheels. Because of the good lateral traction of
the rear axle, this maintains good driving sta-
bility.
If the vehicle is braked close to the locking limit
(full brake application), the ABS starts to oper -
ate . The driver perceives the control process
(which essentially involves pumping the brakes
very rapidly) as a pulsation in the brake pedal
along with an audible noise; this serves as a
warning to adjust the vehicle's speed to road
conditions.
Warning Light
The functional readiness of all the main electrical
components of the ABS is checked by an elec-
tronic monitoring system both before and while
you drive. When the ignition is switched on the
ABS warning light will come on; it should go out
again when the engine is started, at the latest.
If the ABS warning light fails to go out, this indi-
cates that ABS has been deactivated due to a
fault.
/
If the warning light comes on while you are driv-
ing, this indicates that a fault has occurred. In
both cases, normal braking, as in vehicles with-
out ABS, is still retained . The ABS system
should, however, be examined at an Official
Porsche Centre immediately, so as to prevent
the occurrence of further faults which may have
other, unforeseeable, effects.
Note
The ABS control unit is adjusted for the ap-
proved tyre dimensions. Utilisation of non-ap-
proved tyre size can lead to different wheel rota-
tion speeds, which may be interpreted by the
control unit as different vehicle speeds at the
two axles .
If the difference in roll radius exceeds approx.
6%, the control unit will deactivate the ABS and
the ABS warning light will come on.
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