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Are Wheel-Offs Back?

Posted: December 4, 2015 by Rolf Lockwood

Oh, no… are we slipping? It seems that truck and trailer wheel separations have hit the press again, at least in Ontario. This really isn’t good.

There’s no obvious reason to think that much is different elsewhere but I’m not aware of the issue reaching the mainstream media in other parts of the country. Correct me if I’m wrong, dear readers, though I’m not sure I want to know.

Two recent wheel-off incidents along Highway 401 in western Ontario, one of which left a car-driving woman dead, prompted Ontario Transportation Minister Steven Del Duca to call on the trucking industry to step up once again and address the problem before more people are hurt or killed.

According to the London Free Press newspaper, Del Duca is asking the Transportation Ministry to look into ways to improve wheel integrity.

This takes me back 1990 or thereabouts when the problem of flying truck wheels reached near-epidemic proportions in Ontario, after which the province responded with tougher laws, including mandatory training for wheel technicians, and eventually much increased, even rather draconian fines.

I was much involved in the issue at the time and helped create an early version of that wheel-management course that later became the provincial and ultimately the national standard. I’ve been writing about it ever since.

But have we learned nothing? Truck wheel separations in Ontario have increased dramatically from just 47 in 2010 to 148 in 2014.

Back in 1990 the industry simply didn’t understand how easily a truck or trailer wheel-and-tire assembly can come adrift. There was no excuse for such ignorance, but that’s what it was. It certainly wasn’t that the problem appeared overnight, rather that an unhappy set of coincidental circumstances had wheels coming off on busy urban highways, not rolling harmlessly from the Trans Canada into Saskatchewan wheat fields.

If there was no reasonable excuse for ignorance in 1990, there’s none whatsoever in 2015. And given how much attention has been paid to the matter in the intervening years, the only possible conclusion is that laziness, carelessness, complacency — you choose the word — has replaced whatever diligence we once achieved.

There are those who suggest, and I can’t really disagree despite having no proof, that the mainstream, freight-hauling trucking industry performs better on the wheel-off front than do other operations where trucks are more incidental, simply tools required by the job at hand. Those outfits are harder to reach by the authorities, for one thing, tending to do shorter, local hauls that don’t necessarily take them into weigh scales and thus allow them to avoid inspections.

That said, we all know of high-profile, well managed highway fleets that are not immune to complacency on the maintenance front.

So How Does This Happen? 

Not going to spend a lot of time here because the reasons behind wheel-off incidents are at this stage very well known. It almost always comes down to either compromised fasteners, often because of torqueing mistakes, or failed bearings, usually due to improper installation or loss of 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, according to my colleague Jim Park.

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 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 failure of the bearings. Over-tightening (excessive preload) can damage the bearing causing overheating, seal failure, and lubricant loss.

Excerpt from The Lockwood Report. To read past installments or to subscribe, click here

 

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