Don’t lose your wheels

Incorrectly chosen and fitted wheels can pose a major threat to the safety of one’s vehicle and to others on the road.

I was recently reminded of the dangers of wheels coming loose on trucks and trailers. A friend called to tell me about a nasty and frightening experience he had encountered when the left-hand wheel of his caravan came off the axle and bounced across a busy road before ending up in a mielie field. Fortunately no one was hurt in the incident and the damage to the caravan was minimal.

He could not understand how the wheel had come adrift; as he had personally carefully checked the tightness of the wheel nuts the day before he commenced his journey. He had also only travelled 30 km when the nuts came loose and the wheel came off the axle.

On investigation it was found that before the journey the wheels of the caravan had been removed, as they were a little rusted, and sent to a paint shop to be cleaned and powder coated.

During the repainting process thick paint had been applied to the area of the rim where it interfaces with the wheel hub and on the areas where the wheel nuts are seated. Paint softens under the heat, which is generated from braking. The result: the wheel rims and wheel securing nuts quickly became loose and the wheel came off the axle.

I am a firm believer that truck and bus wheel rims should be kept clean and repainted when necessary to keep up a good appearance of the vehicle. But the lesson to be learnt from this story is that when repainting wheel rims the paint on the interface of the wheel rim should be microscopically thin.

Paint on wheel rims is not the only reason that truck and bus wheels come loose. Another common reason is the fitment of wheel rims that are designed for stud mounting onto wheel hubs that are designed for hub mounting.

Many of the older trucks and trailers are fitted with the DIN spherical stud mounting design, which is not interchangeable with the more modern hub-mounted type of rims that are fitted to many of the new trucks. The problem is exacerbated by the fact that the two different rim types look alike and will fit either type of wheel hub. To avoid the incorrect fitment, which could be fatal, it is recommended that commercial vehicle operators clearly identify the different rim fitment types.

To eliminate the problem of loose wheels, and to reduce your vehicle operating costs, the following additional maintenance procedures should be followed:

• Ensure that daily vehicle pre-trip inspections are done correctly and that the inspection includes a careful examination of all the truck and trailer wheels.

• Tighten wheel nuts to the manufacturers’ recommended torque settings using a calibrated torque wrench and follow the proper tightening sequence.

• If a wheel rim is found to be loose, inspect the rim carefully to establish what caused the wheel to become loose and fix the problem.

In addition to the unnecessary costs involved when wheels come loose, a wheel coming off the axle could endanger other road users and, in some incidents, be fatal – much worse than a couple of squashed mielies.

One of this country’s most respected commercial vehicle industry authorities, VIC OLIVER has been in this industry for 49 years. Before joining the FOCUS team, he spent 15 years with Nissan Diesel (now UD Trucks), 11 years with Busaf and seven years with International.