Yamaha FJR13AY 2009, Service Manual

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FEATURES
1-8
The difference between the chassis speed and the wheel speed calculated in the slip ratio formula is
equal to the wheel slip. When the wheel speed is suddenly reduced, the wheel has a tendency to lock.
When the wheel slip and the wheel speed reduction rate exceed the preset values, the ABS ECU de-
termines that the wheel has a tendency to lock.
If the slip is large and the wheel has a tendency to lock (point A in the following figure), the ABS ECU
reduces the brake fluid pressure in the brake caliper. Once the ABS ECU determines that the tendency
of the wheel to lock has diminished after the brake fluid pressure is reduced, it increases the hydraulic
pressure (point B in the following figure). The hydraulic pressure is initially increased quickly, and then
it is increased gradually.
ABS operation and vehicle control
If the ABS starts operating, there is a tendency of the wheel to lock, and the vehicle is approaching the
limit of control. To make the rider aware of this condition, the ABS has been designed to generate a
reaction-force pulsating action in the brake lever and brake pedal independently.
TIP
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.
The higher the side force on a tire, the less traction there is available for braking. This is true whether
the vehicle is equipped with ABS or not. Therefore, sudden braking while cornering is not recommend-
ed. Excessive side force, which ABS cannot prevent, could cause the tire to slip sideways.
WARNING
EW3P61003
The braking of the vehicle, even in the worst case, is principally executed when the vehicle is
advancing straight ahead. During a turn, sudden braking is liable to cause a loss of traction of
the tires. Even in vehicles equipped with ABS, overturning of the vehicle cannot be prevented
if it is braked suddenly.
d d e d e
A
A
B
B
A
A
B
B
A
A
B
B
b
c
a
e
a. Chassis speed
b. Wheel speed
c. Brake force d. Depressurizing phase
e. Pressurizing phase