Wheel loss incidents are relatively rare, but when they do occur, the effects can be devastating. However, diligent checks and simple pieces of technology can help to ensure that wheel nuts stay in their intended position.
This article was originally published in the June 2021 issue of Commercial Vehicle Engineer magazine. To read the full issue, click here.
A pregnant mother and her young daughter had a lucky escape in October 2020. As they ate in a fast-food restaurant in a retail park in Tamworth, Staffordshire, a wheel became detached from a truck cornering a nearby roundabout and bounced into her parked car.
Alex Turrell told the Birmingham Mail she “shuddered to think” what would have happened if she had been in the car at the time. Her car was heavily damaged, and another parked next to it also suffered damage. The truck that lost a wheel didn’t stop.
This example shows what can happen when a wheel detaches from a truck on the move. Some aren’t as lucky as Turrell; estimated figures from Wheely Safe Ltd, which manufactures a sensor that detects loosening when nuts, state there are between 7,500 and 11,000 wheel fixing defects per year, which causes between 150 and 400 wheel detachments, which are responsible for between three and seven fatal accidents.
The DVSA takes a dim view of wheel loss and failures could lead to the suspension or revocation of an O-licence.
For Gary Broadfield, managing director of Wheely-Safe, wheel nuts coming loose is a big issue for the industry, but one that is often downplayed, as operators don’t like to admit to incidents. “There are several thousand incidents per year, but we believe the true figure is a lot worse than that,” he says.
However, Broadfield has sympathy with operators. “Wheels have been around since The Flintstones and if they can’t keep them on now, they will never do,” he says. “But the process is getting harder rather than easier as operators are getting more out of the vehicles – higher weights, frequently using twin wheels, going off-road a lot more, plus there are things like potholes to contend with.
“Some operators follow the most extreme basic routines and schedules of maintenance and even with the best procedures in place you can still get a wheel off and that’s because a nut and bolt is a mechanical solution that has its flaws.
“If you think about a nut, you have to create enough friction to keep it on, but you have to allow the wheel to go on and off, so you have to have clearance around all the holes and that allows for micromovement.
“Micromovement allows for things to start working loose. People believe if they torque the nuts up once a week they will never have a problem, but the vehicle can hit a pothole the next day and it starts working loose and they can [quickly develop] a problem. It is a mechanically deficient way of doing things, but it isn’t going anywhere soon.”
Driver responsibility
As the problems that can occur with wheel nuts are well known, many can be mitigated by good management of wheels, and in recent years, many operators have paid more attention to this, according to Phil Lloyd, Logistics UK’s head of engineering and vehicle standards policy.
“Over recent years, more organisations have moved into contracting out tyre maintenance to, for example, the big tyre companies, and part of that is wheel security and they will torque the wheels properly as opposed to fitting them with an air gun.
“There has been a movement to better wheel security and using torque wrenches and settings and following the guidance. For example, when you change a wheel you re-torque it, which used to be an issue – people would torque it up and that would be it, instead of letting it settle and then re-torquing it.”
However, with such things in place, along with technology like tyre pressure monitoring systems, there is a risk that operators and drivers can become complacent. “The more [aids] you give drivers, the counter to that is that some stop checking things themselves,” he says.
To combat this, periodic refresher training for drivers on what is needed on things like the daily walkaround checks is useful.
“People are a bit loathe to do it because it’s like teaching granny to suck eggs but as long as it isn’t hours and hours, its fine,” says Lloyd.
“My experience is that people who have done their job the same way for years but not been checked tend to fall into bad habits. Sometimes it is just about watching someone go through the motions, then having a conversation with them afterwards.
“People tend to do things their way, and if their way is right, there is no problem, but people can start to miss things and if you ask them afterwards, they don’t always realise.”
Martin Kerry, aftersales director at used car and van dealer Perrys, emphasises that, as with HGVs, the security of wheel nuts on light commercial vehicles (LCV) is the sole responsibility of the designated driver, irrespective of the owner.
“Wheel nut security is essential and forms part of the driver’s daily checks, which can be made simple with the use of wheel nut indicators (WNI),” he says. “WNI are an inexpensive and readily available solution in either most motoring shops or online, and can be fitted within minutes, no skill required.
“It’s very important that LCV wheel nuts are torqued up to the manufacturer’s specification using a calibrated torque wrench because under-torquing can result in loose wheels, whilst over-torquing can stretch the wheel studs, potentially causing the wheel studs to snap.”
While Kerry admits that it may sound like a chore, it should be done. “Give the wheel nuts the respect they deserve.”
But, as Wheely-Safe’s Broadfield notes, vehicles can have diligent inspection routines, and regularly torque the wheel nuts correctly, but incidents of wheels loosening can still happen.
For instance, wheel loss is more common in off-road vehicles. “If a truck is loaded to 40 tonnes and they go down a pothole and all the weight goes through one side or one axle and they have twin wheels and those start working independent to each other, then it can start the process of a wheel nut coming loose,” says Broadfield.
“Other problems occur when too much is when the wheels are on the limit, or when they twin them up, and as soon as you twin stuff up you have more surfaces to play with and you can have the two wheels themselves working against each other if they are not perfectly centred and nuts can just work loose.”
Tech solutions
However, there are solutions that can aid the detection of any wheel nuts coming loose. Wheely-Safe has devised a displacement sensor that sits in a bracket between two wheel studs. “When it is all torqued up that sensor has quite a lot of compression force on it, but the bracket forces it against the wheel rim and that closes a switch,” explains Broadfield. “To open the switch, you need just below one millimetre of movement.
“There is also a heat sensor in there for rim temperatures as that’s a really good indicator for what’s happening behind the wheel with the braking system and the hubs, which is also a valuable element.”
Once the switch has been opened, a message is sent, via a light on the dashboard, to the driver. A message can also be sent to a transport office, although Broadfield advocates always having a driver alert to prevent any potential delays in addressing a problem. This alert goes off before the driver is even aware there is a problem with the wheel nuts, Broadfield adds. The driver can then quickly find a place to stop before the loose nut has a chance to become a problem.
Things like fluorescent WNI are useful to show if a nut is slowly loosening, but sometimes they can loosen very quickly, Broadfield adds. “This device catches those that do work loose quickly,” he says.
“It is an incident-based thing, it isn’t a time-based thing. It is about spotting the incident that happens on the road on a Wednesday afternoon.”
As Broadfield says, the combination of technology, along with daily driver checks and regular scheduled maintenance for wheels and nuts, should ensure that operators do not add to the wheel loss statistics.
This article was originally published in the June 2021 issue of Commercial Vehicle Engineer magazine. To read the full issue, click here.
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