190Driving
Brake assist systems
The brake assist systems ESC, ABS, BAS, ASR and EDL only operate when
the ignition is switched on. They contribute significantly to increasing active
safety.
Electronic Stability Control (ESC)
ESC reduces the risk of skidding and increases the vehicle stability by brak-
ing individual wheels under specific driving conditions. ESC detects critical
handling situations, such as understeer, oversteer and wheelspin on the
driven wheels. The system stabilises the vehicle by braking individual
wheels or by reducing the engine torque.
The ESC has limits. It is important to realise that the ESC is also subject to
the laws of physics. ESC will not be able to deal with all situations with
which drivers may be faced. For example, if the road surface changes sud-
denly then ESC will not be useful in all cases. If the vehicle suddenly enters
a section covered by water, mud or snow then ESC will not provide assis-
tance in the same way as on dry ground. If the vehicle loses its grip on the
ground and moves on a film of water (aquaplaning), the ESC will not be able
to assist the driver to control the vehicle due to the loss of adherence with
the road surface preventing braking and steering. If the vehicle is driven
through series of bends at high speed, the ESC will not always be as effec-
tive: the vehicle reaction to aggressive driving is not the same as at reduced
speeds. When driving with a trailer, ESC does not provide the same amount
of vehicle control as without a trailer.
Adjust your speed and driving style to road, traffic and weather conditions.
ESC cannot push the limits of the laws of physics; improve the transmission
available or maintain the vehicle on the road if a lack of driver attention cre-
ates an inevitable situation. Otherwise, ESC assists in maintaining vehicle
control in extreme situations and uses the movements of the steering made
by the driver to maintain the vehicle moving in the desired direction. If the
vehicle is driven at such a speed that it will leave the road before ESC can
intervene then the system cannot provide assistance. The ABS, BAS, ASR and EDL systems are incorporated into the ESC. The ESC
is always on. The ESC should only be turned off using the ASR button
⇒
Fig. 137 when traction is insufficient. Always remember to turn on the
ASR once more when the vehicle has traction again.
Anti-lock brake system (ABS)
ABS can prevent the wheels from locking during braking until just before
the vehicle stops thus helping the driver to steer the vehicle and maintain
control. This means that, even during full braking, the risk of skidding is re-
duced:
● Press and hold the brake pedal fully. Do not remove your foot from the
brake pedal or reduce braking force!
● Do not “pump” the brake pedal, or reduce braking force!
● Maintain vehicle direction when braking fully.
● When the brake pedal is released or when the brake force is reduced,
ABS is turned off.
ABS control can be observed by vibration of the brake pedal and noise. You
should never expect the ABS to reduce the braking distance under any cir-
cumstances. Braking distances will increase when driving on gravel, recent
snow or on icy and slippery ground.
When driving on loose ground, the all-terrain configuration of the ABS is au-
tomatically turned on. When ABS is activated, the front wheels may lock
briefly. This shortens the braking distance in off-road situations as the
wheels are prevented from digging into loose surfaces. All-terrain ABS only
intervenes when driving in a straight line. When the front wheels are turned,
the normal ABS is activated.
Brake assist system (BAS)
The brake assist system may reduce the required braking distance. The
brake assist system boosts the braking force if you press the brake pedal
quickly in an emergency. As a result, the braking pressure increases rapidly,
the braking force is multiplied and the braking distance is reduced. This en-
ables the ABS to be activated more quickly and effectively.
