Are the chasms and gulches of British Columbia full of wheel-and-tire assemblies that parted company with their tractors and trailers? Are the wheat fields of Saskatchewan populated here and there with flattened spots bearing mysterious imprints like ’11R/24.5′? Are moose in the forests of New Brunswick happily licking salt off hundreds of lost and abandoned truck tires?

Maybe.

The thing is, we don’t know. It’s reasonable to assume that most wheel-off incidents go unreported, especially in Ontario, where draconian laws exist to penalize the guilty. Drivers often don’t even know they’ve lost a wheel until their next circle check. That is, unless the wheel – or, heaven forbid, the whole 400-pound tire, wheel, and hub assembly – smashes into a fellow road user and demolishes his car. Perhaps kills him in the process, as we’ve seen too often in recent months on Ontario highways, where traffic density raises the odds of errant wheels hitting things they shouldn’t.        

Wheel-offs happen across the country, across the world, but they do seem to occur pretty often – or at least they’re more visible – in Ontario. For nearly 20 years the province has had by far the continent’s toughest response to failures in wheel integrity, following a spate of deadly incidents in the mid 1990s, and it’s about to ratchet things up again. (See our new editor John G. Smith’s editorial on page 9 for more on that.)

The thing is, truck wheel separations are on the rise again, from just 47 in 2010 to 148 in 2014, which has demanded a ramped-up inspection effort.

“More than 3,050 trucks and over 29,400 wheel assemblies have been inspected in three recent, targeted wheel inspection blitzes,” said Chris Davies, assistant director of enforcement operations at the province’s Ministry of Transportation. “Additional, unannounced 24-hour wheel-focused blitzes will be conducted.” 

Are we doing it wrong?

Yes, it seems we are, and Davies sums it up this way: “Wheel separations from commercial vehicles are almost always caused by poor maintenance, improper tightening/installation of wheel fasteners, or defective parts,” he told us.

“Keeping wheels on trucks is a shared responsibility and relies on proper installation, maintenance, and inspection. Wheel installers require certification and need to ensure wheels are installed properly, and that only quality parts are used. Truck owners and operators are required to perform routine maintenance to keep vehicles safe. Last but not least, professional truck drivers must inspect their vehicles every day – as required by law – and that includes checking wheels for defects.”

Such advice isn’t new. Way back in 1991 the U.S. National Transportation Safety Board investigated wheel separations and concluded that “…the leading causes of wheel separations from medium and heavy trucks are improper tightening of wheel fasteners and bearing failure; both are the result of inadequate maintenance.”

In 2016, have we learned nothing or grown complacent? You have to think it’s the latter. But things have changed with the advent of very stringent safety laws and what amounts to a no–tolerance approach under the U.S.-based CSA 2010 rating regime. Quite apart from the moral demand that owners keep their trucks safe, the practical need to do so has jumped up the priority ladder a rung or two. 

How does it happen?

The specific reasons behind wheel-off incidents are at this stage very well known. It almost always comes down to either compromised fasteners, often because of torquing mistakes, or failed bearings, usually due to improper installation or lost lubricant.

In 643 U.S. incidents reported between 2000 and 2003, loose wheel fasteners were to blame 65% of the time, while wheel bearings were the cause in 26% of the cases. The remainder were a mix of axle and/or suspension structural failures and other causes.

In terms of wheel fasteners, the culprit is very often laziness, it seems, as impact wrenches are used to run nuts onto studs until they just won’t turn any more. Job done. But not done. A torque wrench has to be used to finish things off because the required clamping force has a very -specific torque value in every case.

Use an impact wrench alone and chances are pretty good that you’ll end up with wheel studs being stretched beyond their yield point. Fractured or worn-out nuts with deformed threads have also been linked to the loss of sufficient clamping force at the nut flange.

People seem not to realize that even a little bit of excess paint, rust, or dirt between the mating areas of wheel-end components will lead to trouble. You’ll start off with low clamping force and things will only get worse from there.

As for wheel bearings, the problem is usually over- or under-tightened bearings or a lack of lubrication. Under-tightening (excessive endplay) can cause the wheel to wobble on the spindle, damaging the seal, which can lead to a loss of -lubricant and eventual bearing failure. Over-tightening (excessive preload) can damage the -bearing, causing overheating, seal failure, and lubricant loss.

Some easy fixes

One example is the simple little Hub Alert decal from Toronto’s Spectra Products, a one-time-use, heat-sensing label that with a simple color change will alert you to an above-normal wheel-end operating temperature. Cheap and apparently effective, assuming someone takes the time to look. The sensor decal will turn from white to black once the hub/hubcap surface has reached the critical temperature.

Catching bearing and seal issues early will reduce the need for over-the-road emergency repairs and will avoid additional and costly repairs due to a failure. Might prevent a fire, for that matter, and could even save a life or two.

The normal operating temperature of hubcap grease or oil should not get above 225°F (107°C), notes Spectra. Dana and Meritor both recommend that, when the temperature reaches 250°F (121°C), you’d better conduct a more detailed wheel-end inspection.

Tools like that are not in short supply.

Take the Safe-T-Loc from Manufacturer Direct in Calgary, for example, designed to warn of a loosened wheel nut before it backs off the stud. It slips over the nut and grips tightly, made of a premium-grade polymer for virtually all two-piece wheel-nut systems. Used in Europe for a few years prior to its introduction here, it was designed by company principal and former fleet-maintenance man Bruce Boyce.

If a fastener should loosen, the Safe-T-Loc will back off in sync with it, but only by six degrees, representing about 45 lb ft of clamping force. At that point a red flag appears to alert the driver or technician that trouble is afoot. But the nut can’t go any further because the Safe-T-Loc is now jammed – and locked – against its nearest neighbor on the adjacent nut. Groupe Robert has bought 267,000 -Safe-T-Loc devices, and Bison Transport has been using them for 12 years. Boyce says there are more than 3 million in Canadian service.

And there’s another Canadian product, the Skirt Nut from Safety Trigo of Brampton, Ontario, invented back in the 1980s by James Holmes, who runs a family–owned trucking fleet there. It replaces the standard flange nut on hub-piloted disc wheels using 22-millimetre studs. It’s claimed to eliminate torque loss while improving tire wear by a minimum of 25%. The nut is made locally.

By replacing the standard flange nut, it will prevent ‘clocking’ or side-slipping of the wheel relative to the nut head. No matter how well or how often a standard flange nut is torqued, Holmes says, torque loss is created if a wheel is allowed to ‘clock’. This can be caused by severe impact with a pothole, a very heavy brake application, a ‘torque twister’ jump start, or stress on the clamped joint resulting from excessive disc flexing. Even a stretch of rough road or an out-of-round tire can cause it, he says.

That clocking action creates vibration because the wheel is rotating out-of-round to the hub. In turn it causes loosening as the nut threads begin to vibrate against the stud’s threads, followed by accelerated ‘clocking’ that’s often severe enough to damage and elongate the stud hole, damage the stud, and cause rapid torque loss. If not checked the result will be a catastrophic loss of wheel-end components.

The Skirt Nut prevents that side-sliding, stress flexing or clocking, so the flange nuts simply won’t loosen, even under heavy load conditions or severe road vibration. Holmes’ solution was to build a nut that had a shank or ‘skirt’ that partially penetrates each bolt hole, in effect filling the space between the stud hole and the stud, eliminating the possibility of the wheel moving on the studs.

None of these inexpensive fixes can replace proper maintenance practices, of course. And there’s absolutely no shortage of advice and easy-to-access training -materials. Leaves no excuse for not doing it right. 

For More Information: 

Michelin has teamed up with the Tire Industry Association to produce three terrific videos covering just about every aspect of truck and trailer wheel integrity.
A simple online search will uncover dozens more, but these three do the job awfully well: 

www.youtube.com/watch?v=wrsj2UoMeys

www.youtube.com/watch?v=n1sZ5OAcaFc

www.youtube.com/watch?v=ETOAVzB2cOw

Also See:

Hub Alert

www.spectraproducts.ca

Safe-T-Loc

www.mdltd.ca

Safety Trigo

www.safetytrigo.com