Automatic Stability Control (Asc) - BMW R 18 B 2021 Rider's Manual

112 TECHNOLOGY IN DETAIL
Reserves for safety
The potentially shorter stopping distances
which BMW Motorrad full integral ABS
permits must not be used as an excuse
for a careless riding style. ABS is primarily
a means of ensuring a safety margin in
genuine emergencies.
WARNING
Braking in curves
Risk of accident despite ABS
The rider is always responsible for
adapting his/her driving style.
Do not reduce the additional safety
function with careless riding or
unnecessary risks.

AUTOMATIC STABILITY CONTROL (ASC)

How does ASC work?
BMW Motorrad ASC compares the wheel
centrifugal velocities of the front and rear
wheels. The speed difference is used to de-
termine the slip rate, and thus the stability
reserves at the rear wheel. The engine con-
trol adapts the engine torque when the slip
limit is exceeded.
WARNING
Risky riding style
Accident hazard despite ASC
The rider is always responsible for
adapting his/her driving style.
Do not reduce the system's extra safety
margin with careless riding or unneces-
sary risks.
Special situations
As lean angles increase, acceleration capa-
bility is also progressively restricted by the
laws of physics. This can result in delayed
acceleration when exiting very tight turns.
Even in special riding situations, e.g. high
speeds, an unfavorable loading configuration
or overload, BMW Motorrad ASC is capable
of influencing the engine torque.
The system compares the rotational speeds
of the front and rear wheels to detect any
tendency for the rear wheel to spin or lose
traction. If the system detects implausible
values for an extended period of time, it will
switch off the ASC functionality as safety
precaution and a display will alert you to an
ASC error. A self-diagnosis must be com-
pleted before the fault memory entry will be
displayed.
In the following unusual riding conditions,
the BMW Motorrad ASC may possibly
switch off automatically.
Unusual riding conditions:
Riding on the rear wheel (wheelie) for an
extended period with ASC deactivated
Rear wheel spinning when stationary with
front wheel brake engaged (burn-out)
Warm-up on auxiliary stand at idle speed
or with gear engaged
ASC is reactivated by turning the ignition
off and on and then riding at a speed above
3 mph (5 km/h).
If the front wheel loses contact with the
ground under extreme acceleration, the ASC
reduces the engine torque, maintaining the
reduction until the front wheel makes con-
tact with the ground again.
BMW Motorrad recommends that you re-
spond to this condition by twisting back the
throttle grip somewhat to return to stable
dynamic operating conditions as quickly as
possible.
Slippery road
On very loose surfaces (e.g. sand and snow),
the interventions of the ASC can reduce the
drive force at the rear wheel to such a de-
gree that the rear wheel no longer turns suf-
ficiently. In this case, BMW Motorrad recom-
mends switching off the ASC temporarily.
Note that the rear wheel will spin on the
loose surface, and close the throttle grip in
a timely manner before reaching a solid sur-
face.
Then switch on ASC again.