Download BMW ONBOARD COMPUTER Technical data

Brake system with
BMW Motorrad ABS
70
How does ABS work?
Engineering details
6
z
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 friction, the longer the braking distance.
If the rider increases braking
pressure to the extent that braking force exceeds the maximum
transferable limit, the wheels start
to lock and the vehicle loses its
directional stability; a fall is imminent. Before this situation
can occur, ABS intervenes and
adapts braking pressure to the
maximum transferable braking
force so the wheels continue to
turn and directional stability is
maintained irrespective of the
condition of the road surface.
What are the effects of
surface irregularities?
Surface irregularities can cause
the wheels to lose contact temporarily with the road surface. If
this happens the braking force
that can be transmitted 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 regain
contact with the road surface.
At this instant the ABS must
assume an extremely low coefficient of friction, so that the
wheels will continue to rotate under all imaginable circumstances,
because this is the precondition
for ensuring directional stability.
As soon as it registers the actual
circumstances, the system reacts instantly and adjusts braking
force accordingly to achieve optimum braking.
Rear wheel lift
Under very severe and sudden
deceleration, however, it is possible that the ABS will be unable
to prevent the rear wheel from
lifting clear of the ground. If this
happens the outcome can be a
highsiding situation in which the
motorcycle can flip over.
Severe braking can cause
the rear wheel to lift off the
ground.
When you brake, bear in mind
that ABS control cannot always
be relied on to prevent the rear
wheel from lifting clear of the
ground.