Accidents waiting to happen
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The threat of wheel loss can be a frightening experience for drivers. What can they do to help prevent it? CM reports Words: Guy Sheppard Once let loose on the road, a lorry wheel can act like a bouncing bomb, hitting anything that stands in its way with incredible force.
Road safety charity Brake’s website outlines several examples of this happening, including one case where the driver failed to notice when an outer wheel lew off into a ield because of the noise from his tipper truck. Less than a mile later, the inner wheel worked its way off, killing a pensioner while she waited at a bus stop.
Drivers themselves are potential victims. If wheel loss causes a sudden loss of control, it will endanger their life as well as putting their vehicle and load at risk.
Transport research specialist TRL estimates that in a typical year at least 150 lorry wheels become detached due to ixing defects, causing at least 10 injury accidents and at least three fatalities.
Drivers’ attitudes to the risks posed by wheelnuts loosening are also cause for concern. In a questionnaire involving more than 500 drivers, TRL found that nearly a third admitted to not always looking for tell-tale signs of this happening.
This may explain why, according to latest annual igures, nearly one in 50 of all vehicles inspected by VOSA during spot checks was given a prohibition for defective wheels and hubs. The proportion of trailers was around one in 30. TRL’s research was undertaken for the Department for Transport nearly ive years ago, but Martin Dodd, one of the authors, says he has seen nothing since to suggest the situation has changed.
Drivers need to take the issue seriously for their own safety as well as that of other road users. So what do they need to know to prevent what is potentially one of the most frightening experiences that can happen to them on the road?
Causes of wheelnut loosening
According to a best practice guide on wheel security, published jointly by the Freight Transport Association (FTA) and Institute of Road Transport Engineers (IRTE), vibration, cornering, heat, acceleration and braking all put pressure on wheelnuts. No vehicles are therefore immune from the problem. “If one wheelnut loosens, then these forces are distributed over the remaining nuts,” says the guide. This causes adjacent nuts to loosen as well, weakening the clamping force between the stud, nut and wheel and thereby speeding up the whole loosening process. A tipper operator, who asked to remain anonymous, told CM that although his company does both distance and site work, the type of work does not determine whether wheelnuts become loose or not.
Because drivers have a legal responsibility to ensure that the vehicle they use on the public highway is free from visible defects, they should always carry out a visual inspection of the wheels for security. It is no excuse to simply blame maintenance staff when things go wrong.
The most obvious sign of a loosening wheelnut is when the wheelnut indicator becomes misaligned, but not all trucks have these itted. Other clues include bright metal around the seating area of nuts and washers, elongation of the stud holes and signs of cracking to wheels, nuts and washers. Rust radiating out from the area of the nut and washer should also be of concern. The FTA/IRTE guide says drivers are legally required to report any defects in writing and that the vehicle should not be driven without the defect being investigated and rectiied.
Wheel fitting and tightening
There are several factors to take into account when wheel itting and tightening. Too much tightening can stretch and break the studs or pull them through the wheel hub. Insuficient tightening allows the wheel to fret and wear. According to the FTA/IRTE guidance, the work should ideally be done when the wheel is cold to take account of expansion and contraction of components. There is a correct sequence for tightening each nut and the torque wrench must be set according to the manufacturer’s instructions, using a socket of the correct size and depth.
Due to resettlement of the various components involved, the guidance says that wheelnuts must be rechecked for tightness using a calibrated torque wrench within 30 minutes of the wheel being itted or after the vehicle has travelled up to 80km. Some operators put a removable tag on the wheel as a reminder that this needs to be done.
Training
Andy Macrae, a member of the Road Haulage Association technical committee and, until recently, TDG southern leet engineer, irmly believes that this work should not be done by drivers. “It’s not beyond the realms of a driver, but tyre itters are trained to do re-torquing.” He adds that his experience of giving drivers torque wrenches is that they tend to over-tighten, resulting in a lot of sheared wheelnuts. The FTA/IRTE guidance supports this view. “It is often an unconscious act for drivers and maintenance staff to over-torque wheels in the misguided belief that exerting extra pressure on a wheel ixing will prevent them from coming loose.” However, the tipper operator CM spoke to argues that drivers are more than capable of doing the checks themselves. “Our drivers are under instruction to physically check wheelnut security at 50km after wheels have been removed for tyre changes or punctures. An experienced HGV driver with a measured length bar and brace is, in my estimation, able to keep wheelnuts within safe operational levels of tightness.”
Legal implications
VOSA inspects wheels as part of its roadside enforcement activity and blames weakened wheel security on poor maintenance and inadequate driver checks. Lucy Wood, a Rothera Dowson transport lawyer, says drivers would receive a £60 ixed penalty and three penalty points for the offence. “If, however, the use of the vehicle resulted in an accident, he could be taken to court not only for that offence, but also possibly for dangerous driving.” The driver would then be disqualiied from driving if convicted.
In the event of a wheel simply rolling to the side of the road, Wood advises the driver to contact their employer and arrange to have the vehicle repaired. If someone is injured other than the driver or damage is caused to someone else’s property, then the driver must stop and give his name and address. If unable to do this, then the accident should be reported to police within 24 hours. ■