General instructions
To find out more on the subject
of engineering go to:
bmw-motorrad.com/technik
Anti-lock brake system
How does ABS work?
The amount of braking force that
can be transferred to the road
depends on factors that include
the coefficient of friction of the
road surface. Loose stones, ice
and snow or a wet road all have
much lower coefficients of friction
than a clean, dry asphalt surface.
The lower the coefficient of fric-
tion, the longer the braking dis-
tance.
If the rider increases braking
pressure to the extent that brak-
ing force exceeds the maximum
transferable limit, the wheels
start to lock and the motorcycle
loses its directional stability. A
fall is imminent. Before this situ-
ation can occur, ABS intervenes
and adapts brake pressure to
the maximum transferable brake
force, so the wheels continue to
turn and driving stability is main-
tained irrespective of the condi-
tion of the road surface.
What are the effects of
surface irregularities?
Humps and surface irregularit-
ies can cause the wheels to lose
contact temporarily with the road
surface; if this happens the brak-
ing force that can be transmit-
ted to the road can drop to zero.
If the brakes are applied under
these circumstances the ABS
has to reduce braking force to
ensure that directional stability is
maintained when the wheels re-
gain contact with the road sur-
face. At this instant the ABS
must assume an extremely low
coefficient of friction, so that the
wheels will continue to rotate un-
der all imaginable circumstances,
because this is the precondition
for ensuring directional stability.
As soon as is registers the ac-
tual circumstances, the system
reacts instantly and adjusts brak-
ing force accordingly to achieve
optimum braking.
Rear wheel lift
Even under severe braking, a
high level of tyre grip can mean
that the front wheel does not
lock up until very late, if at all.
Consequently, ABS does not in-
tervene until very late, if at all.
Under these circumstances the
rear wheel can lift off the ground,
and the outcome can be a high-
siding situation in which the mo-
torcycle can flip over.
7
64
z
Engineering details
To Next Page
Loading...
Need help?
General
