Page 52 - The Tyreman V46 2015-4
P. 52
In a properly aligned vehicle, all the axles should be perpendicular to the frame and parallel to each other and all the wheels should track the front wheels. Tandem drive axles that are not parallel to each other or axles that are not perpendicular tyre wear.
Rear tandem axles that are not perpendicular to the frame but are parallel to each other create a “thrust angle” that tends to push the vehicle off course.
The driver feels the vehicle pulling in the direction the drive axles are angled and must steer in the opposite direction to keep the truck travelling in a straight line. The steer axle tyres are constantly subjected to ‘scrubbing’, or side forces, as they correct the direction of travel of the truck, which results in fast and irregular wear.
Trailers need to be aligned too!
This out-of-parallel condition on trailers known as ‘dog tracking’ is often seen on our Malaysian roads. It is quite visible as you follow the vehicle down the highway, since the trailer appears to be travelling at an angle to the tractor. The driver can see one side of the trailer in his mirrors, but not the other. He feels the vehicle ‘wandering’ and must make constant steering corrections to keep driving straight ahead.
Tyres on a trailer with this condition are dragged sideways a few feet for every mile of operation. In severe conditions this can result in dragging the trailer tyres side- ways thousands of miles for every 100,000 miles the vehicle runs. This is called ‘tyre scrub’ and results in fast and irregular trailer tyre wear. The same side shoul- ders on all the tyres on the trailer axle will be worn and will exhibit one-sided wear.
Tandem skew or scrub angle occurs when tandem axles are not parallel to one as well as the driver to determine the direction the vehicle will go. Trailer axles with tandem skew will be dragged in different directions.
This condition is the worst type of misalignment and will cause excessive and rapid tread wear on all the tyres of a vehicle. This condition can cause fuel consumption to increase by more than 8 per cent and the incessant scrubbing causes the tyre wear to increase substantially too.
拖车也必须进行定位!
Total Wheel Alignment as in All Axles and Wheels Alignment for rigid trucks, trac- tors and semi-trailers is seen as the only way forward.
Manbeni Machine Tools (M) Sdn Bhd, the sole distributor of Josam frame straight- ening and wheel alignment equipment from Sweden.
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