The Brake Disc Wiper; The Vehicle/Trailer Stabilisation System - Volkswagen Passat 2006 Service Training

Running gear

The brake disc wiper

A film of water may form on the brake disc in severe
rain or if the road is wet, for example; this reduces the
coefficient of friction between the brake disc and the
brake pads on braking. As a result, the braking effect
is temporarily changed until the water film is
dissipated by frictional heat.
This is combated by the new function in the ESP system
– the brake disc wiper.
< 2 bar
The vehicle/trailer stabilisation
system
A vehicle/trailer stabilisation system will be launched
in the Passat 2006 along with the TRW EBC 440 ESP
system.
This function is an ESP sub-system.
An unstable vehicle/trailer is stabilised by specifically
braking the wheels.
The towing vehicle's yaw rate and steering angle are
used as input variables to achieve this.
52
15 wheel revolutions
Start of
execution
By regularly applying the brake pads to the brake
discs from time to time at low pressure, this displaces
the water film and shortens the stopping distance.
This is carried out by cyclical initialisation of the
hydraulic pump, which builds up the low brake
pressure in the brake system.
This process in the brake system is not perceptible to
the driver.
5 min
End of
execution
The trailer's pendulum movements are passed on to
the towing vehicle. This leads to yawing moments and
lateral forces which are detected by the yaw rate
sender and the steering angle sender and are
processed in the ESP control unit.
The vehicle/trailer's instability is combated by
building up pressure in the system and actuating
individual valves in the ESP hydraulic unit.
15 wheel revolutions
Time/distance
S339_145