Yamaha tmax XP500A, Service Manual

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GEN
INFO
FEATURES
EAS00874
Brake force and vehicle stability
When the brake pressure is increased, wheel
speed is reduced. Slip occurs between the tire
and the road surface and brake force is gener-
ated. The limit of this brake force is determined
by the friction force between the tire and the
road surface and is closely related to wheel
slippage. Wheel slippage is represented by the
slip ratio.
Therefore, side force is also closely related to
wheel slippage. See figure
È
. If the brakes are
applied while keeping the proper slip ratio, it is
possible to obtain the maximum brake force
without losing much side force.
ABS allows full use of the tire capabilities even
on slippery road surfaces or less slippery road
surfaces. See figure
É
.
È
Brake force
Side force
Slip ratio (%)
Friction force between the tire and road su
rface
É
Friction force
betwee
n the
tire and road surface
Less slippery
road surface
Controlling zone
Slippery road surface
Slip ratio (%)
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
vehicle 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).
Vehicle speed
Wheel speed
Pressurized
Depressurized
Brake force