APRILIA SHIVER 900, Service Station Manual

Page: 361 / 444

•
With the system in stand-by mode, the ABS processor controls the wheel speed instant by
instant to assess any slippage of the wheels.
•
When in standby, the system does not intervene at all when the rider brakes; the braking
system is the same as the one without ABS.
ABS Cycle phases (the following operations refer to the front circuit but they are also valid for
the rear):
A - Brake activation: the rider starts braking as he would usually do.
B - Pressure reduction: coincides with the recognition of the dangerous situation (wheel slippage
exceeds the threshold): the system closes the inlet valve (10-12) and opens the exhaust valve (13-15)
temporarily.
At this stage the rider cannot increase the pressure on the callipers (8-9) and the system reduces the
pressure on the callipers partially. The excess fluid temporarily fills the front reservoir (18-19) until the
ABS pump (17) self-activates and delivers the fluid back to the brake pump (2-5).
C - Maintaining pressure: the pressure in the callipers (8-9) remains low until total recovery of speed /
wheel grip.
The system restores the fluid taken from the calliper (8-9) in the section of the system between the
brake pump (2-5) and the ABS inlet valve (10-12).
D - Pressure restoration: by opening the inlet valve (10-12) momentarily, the pressure of the callipers
(8-9) is increased until maximum deceleration is reached. Then, the system gives the control over the
braking back to the rider.
E - If the wheel does not reach complete grip, the system continues operating as before until complete
grip is obtained or until the vehicle stops. An error may be shown in the event that the duration of the
pressure reduction phase exceeds a predetermined time limit.
ABS SYSTEM DESCRIPTION
The ABS system is a device to avoid wheels locking in case of emergency braking, increasing vehicle
braking stability when compared to a traditional braking system.
The ABS system enhances control over the vehicle, taking into consideration never to exceed the
physical limits of vehicle grip on the road. The rider is fully responsible for riding at a suitable speed
based on weather and road conditions, always leaving an appropriate safety margin. Under no circum-
stances can the ABS system compensate for the rider's misjudgement or improper use of brakes.
Sometimes when the brake is operated, the tyre locks with a consequent loss of grip, which makes it
difficult to control the vehicle.
A position sensor (3) on the tone wheel (2), forming an integral unit with the vehicle wheel, "reads" the
status of the vehicle wheel spotting any possible lock.
SHIVER 900
Braking system
BRAK SYS - 361