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IW4/IW7 WB/WBV Description
D1 0412BA1-GB04 3
As the brake characteristics depend on the rotating direction of the wheels (the brake linings and
brake drums are ground in forward direction), only the brake torque of the wheel rotating in
forward direction is measured. For this reason, the brake test has to be done separately for each
wheel.
In order to obtain a reliable comparision between the brake forces of both wheels of the same
axle, the same pedal force will have to be applied at the brake test of the left and right wheel. To
accomplish this, a pedal force meter can be connected to the vehicle's brake pedal.
It is also possible to measure the current pressure Pm of the hydraulic brake by means of a
pressure sensor.
Testing of various 4-wheel drive types
There are three different types of 4-wheel drives:
a) Disengageable drive shaft leading to the differential
b) Visco-clutch (VC) in the drive shaft leading to the differential
c) Rigid drive shaft between the differentials
a) Disengageable drive shaft leading to the differential
On vehicles equipped with non-permanent 4-wheel drive, the brakes are tested with the 4-wheel
drive switched off, just like vehicles with only one drive axle.
b) Visco-clutch (VC) in the drive shaft leading to the differential
There are two different Visco-clutch types. The soft Visco clutch has a higher torsibility
(viscosity) than the hard Visco clutch, therefore no torque is transferred to the other wheels
when the drive shaft rotation is low.