Daf LF.book - Peterbilt Motors Company

Driving
STEERING
The steering gear is hydraulically assisted. As excessive pressure may damage the
hydraulic pump, stop turning the steering wheel when the wheels are at full lock or
are blocked by an obstacle. The steering gear may be damaged, if this is ignored.
RAS-EC SYSTEM
The RAS-EC system is an electronically controlled, speed dependent steering
system for the trailing axle. This steering system reduces the turning circle and tire
wear to a minimum.
In contrast to the mechanically steered axle, the RAS-EC system has no steering
linkage, but speed dependent, electronic-hydraulic steering by means of a steering
cylinder.
Speed-dependent
At speeds of up to 15 km/h (9mph), the trailing axle co-steers with the front axle,
both in forward and reverse direction. Above 15 km/h (9mph) the steering effect is
gradually reduced until 38 km/h (23 mph) is reached. Above 38 km/h (23 mph) the
trailing axle is fixed exactly in the centre position. This means that at higher speeds
optimum direction stability is ensured.
Faults
If a less serious fault occurs, the trailing axle is fixed in the centre position. The
trailing axle will no longer co-steer.
If a serious fault occurs, the complete RAS-EC system will be switched off. The
trailing axle is no longer activated but is forced to co-steer.
Note:
In the event of a serious fault, reversing is impossible. Due to friction between tire
and road surface the trailing axle will steer maximum in an uncontrolled manner.
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