GSF1200AK6/SAK6 (’06-MODEL) 5
INTRODUCTION
ABS (Anti-lock Brake System)
This system not only prevents the wheels from locking while braking, but also provides more stable braking
by controlling the wheel speed so as to maximize the friction between the tires and road surface. If the
wheels lock up, the motorcycle cannot be steered and may fall over. If this occurs on a slippery road that has
surface with a low friction coefficient, such as on a wet or gravel-covered road, it is very difficult even a
skilled rider to determine the braking efficiency correctly.
This system monitors the wheel speed and controls the braking force even while ridding on slippery roads or
when braking suddenly during an emergency. The main components of this ABS are: the front and rear
wheel speed sensors, and ABS control unit/hydraulic unit (HU) that are combined into one. These compo-
nents work together to optimize braking.
BASIC ABS PRINCIPLES
In order to understand the operation of the ABS, it is necessary to understand the movement and character-
istics of the motorcycle and its wheels, during braking. The necessary terminology and theory are explained
below.
SLIP RATIO
While the motorcycle speed is constant, the wheel speed is
equal to the motorcycle speed. However, applying the brakes
adds a braking torque which decreases the wheel speed, result-
ing in a difference between the wheel speed and the motorcycle
speed. This causes slipping between the tire and the road sur-
face. The slip ratio is defined as the difference between the
motorcycle speed and the wheel speed, divided by the motorcy-
cle speed and expressed in percents. The slip ratio (λ) is there-
fore expressed as follows:
λ = (V – Vw) / V × 100 (%) . .
1
Vw = ω · r. . . . . . . . . . . . . . . .
2
From
1 and
2:
λ = (V – ω · r) / V × 100 (%)
λ : Slip ratio
V : Motorcycle speed
Vw: Wheel speed
ω : Angular velocity
r : Wheel radius
Wheel Speed Sensor Measures the wheel speed.
ABS control unit Calculates the ideal wheel speed from the measured wheel speed and
commands the HU to decrease, increase and maintain the brake fluid
pressure.
Hydraulic Unit (HU) Decreases, increases and maintains the brake fluid pressure according to
the ABS control unit.
SAMPLE
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