6
Inspection and adjustment
BALANCING OF VEHICLE COMBINATIONS
2-1
2. INSPECTION AND ADJUSTMENT
2.1 MEASURING WITH A DYNAMOMETER
Make sure the vehicle combination is in laden
condition.
A vehicle in laden condition will result in
accurate measurements. The tolerances of the
various brake-system valves are small when the
vehicle is laden.
Furthermore, the maximum braking
performance will be achieved when the vehicle
is in laden condition.
Write down the braking forces of the various
axles at the following braking pressures,
measured at the service-line coupling head:
p = 0.5 1.0 1.5 2.0 3.0 4.0 5.0 bar
The combination is correctly balanced if the
braking performance at 2 - 3 bar for the tractor
and the (semi-)trailer are at the same position in
the appropriate so-called EC band, i.e. both in
the upper part, both in the lower part or both in
the middle part. The bands (curves) and how to
fill these out are mentioned below.
A correct balance can be obtained by adjusting
the braking-pressure advance in the
(semi-)trailer reaction valve. Often, it is also
possible to adjust the braking-pressure advance
in the (semi-)trailer brake valve (on the
(semi-)trailer).
For optimum interchangeability of vehicles, the
correct choice between these two alternatives
must be made.
Truck or tractor
Increasing the braking-pressure advance at the
(semi-)trailer reaction valve will decrease the
deceleration of the motor vehicle, because:
increasing the braking-pressure advance will, at
an equal pressure at the reaction coupling head,
result in a lower braking-cylinder pressure (and
therefore less braking force) in relation to the
towed vehicle.
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