Porsche 911 turbo Owner's Manual page 38

WARNING
ln
spite of the improved handling
afforded
i
by
the
ABS
system,
it
still
remains
the ie-
sponsibility of the driver to adapl the drivingl
style to
the prevailing road and weather
con-
ditions,
as
well
as,
obeying
traific laws.
ln
no case. should
the
higher degree
of
safety
r
offered
by ABS be
regarded
as â justifica-
,tion
for taking greater
risks, Other
vehiclesr
not equipped wrth
the ABS system may
not
be
able
to
maintain
control,
especially on
wet or poor road surfaces and thus may
be
r
more likely
to
impact
you in the
rear. To
ABS Brake System
(Antilock brake system)
The ABS system represents
a
major contribu-
tion to the
enhancement
of
active safeiy
in
your vehicle. This system
prevents the wheels
from locking in a
panic
stop on almost all road
su
rfaces.
With
ABS
system in your
vehicle,
the
fol-
lowing
areas are enhanced:
Full
steerability, vehicle remains
steerable
under
all
braking forces.
Good directional control,
no
swerving
caused
by
locking
of
wheels under
braking
conditions.
36
Excellent stopping distance,
stopping
dis-
tances
are usually reduced because
control-
led braking is
maximized.
Prevention
of wheel lock up, no
brake-in-
duced sliding and
thus no
localized
tire
wear
from emergency braking.
The crucial advantage
of ABS system over
a
conventional
brake system
is in the
area
of
maintaining directional control
and
maneuver-
ability
of the car
in
emergency situations,
in-
cluding panic
braking in turns.
Driving with
the ABS System
A
wheel speed sensor is fitted
to
each of the
four wheels. lf wheel slippage of either of
the
front
wheels
or the rear
wheels
is
sensed
during braking,
the brake pressure is
adjusted
automatically until
the wheel no
longer
slips.
The brake pressure is
regulated
for each front
wheel individually and for both rear
wheels
to-
gether.
On
a
road
surface
which
is
slippery
on
only
one side,
the rear wheel which
is
braking
on
the
slippery surface determines
the
brake
pressure which will be applied equally
to
both
rear
wheels. This ensures that directional sta-
bility
is maintained. However,
if
braking force
approaches the
wheel locking-up point for
all
wheels (panic braking)the ABS system will
in-
tervene
in a way
comparable
with rapid
ryth-
mic
braking.
The proper operation
ol ABS
is
perceived
by the driver as
a pulsating
brake
pedal
in
conjunction
with audible
no
se
anc
perhaps some vibration. The driver is
thereby
warned
to
reduce vehicle
speed
appropriate
for
the prevailing
road conditions.
The functional readiness of all the main
elec-
trical components
of the ABS is
checked
by
an
electronic monitoring
system both
before
and while
you
drive. When
the
ignition
is
switched on
the ABS warning lamp and
the
central warning lamp
will light up; they
should
go out
again
when
the
engine
is
started,
at
the latest. lf the ABS warning lamp fails
to go
out, this indicates
that ABS has
been
deacti-
vated due to
a fault. lf the warning lamp
Iights
up while
you
are driving,
this indicates that
a
fault has
occurred.
ln
both cases,
normal
braking, as in vehicles without ABS,
is
still
re-
tained. The ABS system should, however,
be
examined
at an authorized Porsche dealer im-
mediately to
prevent the occurrence of
further
faults.
Note
The control unit of the ABS brake system
is
set
for
standard
tire
sizes.
lf
non-stand-
ard tires
are
fitted, the control
unit
may
misinterpret
the
speed
of the vehicle,
be-
cause
of the variant data
it
receives from
the sensors on
the
axles.
lf
the
difference
in rolling
radius
exceeds
approx.
6
%,
the control unit
deactivates
the
ABS system
and the ABS
warning
lamp
lights
up.
sJ
ed
èd
èe
èâ
è4
E
:z
-
-é -
a=
è=
è4
è=
e=
È=
e=
2=
e=
É=
Lz
e"
Et
Éz
e=
ut
L
E-