Yamaha 2003 FJR1300, Service Manual

Page: 69 / 162

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CHAS
EAS00875
Wheel slip and hydraulic control
The ECU (ABS) calculates the wheel speed of
each wheel according to the rotation signal
received from the front and rear wheel sen-
sors. In addition, the ECU (ABS) calculates the
motorcycle chassis speed and the rate of
speed reduction based on the wheel speed
values.
The difference between the chassis speed and
the wheel speed calculated in the slip ratio for-
mula is equal to the wheel slip. When the
wheel has a tendency to lock, the wheel speed
is suddenly reduced. When the wheel slip and
the wheel speed reduction rate exceed the
preset values, the ECU (ABS) determines that
the wheel has a tendency to lock.
If the slip is large and the wheel has a ten-
dency to lock (point A in the figure), the ECU
(ABS) reduces the brake fluid pressure in the
brake caliper and increases the pressure of
the brake fluid in the brake caliper when the
tendency to lock has diminished (point B in the
figure).
Motorcycle speed
Wheel speed
Pressurized
Depressurized
Brake force
EAS00876
ABS operation and motorcycle control
If the ABS starts operating, there is a tendency
of the wheel to lock, and the motorcycle is
approaching the limit of control. To make the
rider aware of this condition, the ABS has been
designed to generate a reaction-force pulsat-
ing action in the brake lever or brake pedal.
NOTE:
_
When the ABS is activated, a pulsating action
may be felt at the brake lever or brake pedal,
but this does not indicate a malfunction.
ANTI-LOCK BRAKE SYSTEM (FJR1300A)