Get Behind the Wheel: Truck wheel maintenance practices that make a difference
Posted: February 13, 2019 by Eric Berard
Even tire pressure is a consideration when looking to ensure that fasteners maintain their integrity.
MONTREAL, Que. – There are plenty of benefits to well-maintained wheels. They’re safer, to be sure, less likely to escape their bonds and go skipping across a highway. Something as simple as a clean appearance can help to make a lasting impression on customers as well.
The most obvious wheel-related issues – like loose, missing, or broken fasteners – are spotted during pre-trip inspections. But there is also a place for thorough spec’ing procedures, in-shop inspections, and ongoing maintenance.
While steel wheels are way cheaper – up to three times cheaper — than their aluminum counterparts, they require more maintenance to fight corrosion. They’re also heavier, which has an impact on payload and revenue in weight-sensitive applications.
Spec’ing the right wheel load rating will also have major maintenance impacts down the road. Though less common than problems relating to studs or lug nuts, wheel overload is another threat to their integrity.
Once the tire has safely been dismounted, any wheel needs to be cleaned of road salt or any dirt – including rust chips – that could hide their actual condition. “A lot of times, a wire brush takes care of it right away,” says Brandon Uzarek, field engineer at Accuride.
Inflation valve stems should also be replaced with each tire removal. Removing the valve will let you know if any corrosion has formed around its hole, and replacing it is an inexpensive way to avoid tire inflation issues. “They’re pretty cheap and it’s cheap insurance but if you use the same valve stem again, you don’t know if that O-ring inside of it is worn out or brittle,” says Brian Thomas, marketing communications manager at Alcoa, noting that valve condition is too often overlooked.
Once the wheel is clean and free of a valve, the inspection should involve looking for cracks in metal, elongated bolt holes, torch cuts, rim damage in the bead seat contact area, and bent flanges or components, Uzarek says. Any form of crack or sign of altered integrity should lead to a wheel being put out of service.
Don’t attempt to weld a damaged wheel, whether steel or aluminum. The related heat could do more harm by modifying structure and durability of the wheel, Uzarek warns.
Attention should also be paid to the condition of fasteners. Any damaged pieces should be replaced and the new ones lightly lubed with a drop of engine oil before being tightened again.
Wheel manufacturers agree that the correct tightening torque for most applications should be somewhere between 450 and 500 lb-ft. Calibrated air or hand wrenches are essential to take any guesswork out of the equation.
“In addition, wheel torque should be checked 50-100 miles [80 to 160 kilometers] after a tire change, using a calibrated torque wrench to ensure proper torque,” says Jayne Orr, Accuride’s vice-president, sales — regional and aftermarket.
Elongated bolt holes will often indicate that a stud was under-torqued, while damaged threads could show the opposite, Thomas says.
Uzarek adds that, beyond fasteners, over-torquing can damage the wheel itself. “The flange on the nut can dig into the face of the wheel, creating a stress riser where cracks can initiate,” he says.
Wheel flanges should also be inspected for signs of uneven wear. “Aluminum wheel flange wear could cut the tire. Vehicles with a high center of gravity are prone to this condition,” says Michael Palladino, director/product management at Accuride. Many wheel manufacturers offer pretty simple gauges that indicate if both flanges are even, although a carpenter’s square can also be used.
Though powder coating on steel wheels has progressed over the years, any model will need to be painted again at some point. The wheels can be sent back to the manufacturer for refinishing, although some people prefer taking care of it themselves. But there are guidelines to follow if that’s the case.
“The coating should be stripped in a way that does not damage the thickness or material properties of the steel. Burn-off ovens are not recommended,” Uzarek says, adding that bead blasting can be a good alternative to remove any trace of old paint or corrosion.
When wheels are repainted, the final result should be a flat, smooth, and well-cured texture, no thicker than 3.5 mils (0.0035 inch). “Thick and under-cured paint can cause issues with clamping force when the wheel returns to service,” Uzarek explains.
Despite its wide use in truck components, galvanization as a mean of coating steel wheels instead of paint isn’t the solution, at least yet, according to Orr.
“We have done some testing that shows that the galvanization process can actually degrade the mechanical properties of the wheel. There’s a layer between the steel and the galvanization where it can become very brittle,” she says, adding that any time something brittle is against steel, it can lead to cracks.
Moisture infiltration is another threat, and that’s why Alcoa’s Thomas isn’t a big fan of the aero wheel covers that have become fashionable lately. He refers to how they might trap dirt and moisture inside. “Then you get potentially problems with hubs and with rusting of the hubs, the brakes and all of that,” he says.
Then there’s the fact that they can block the view of fasteners.
“You don’t know if the lug nuts are on, or if they’re tight; you can’t see them. It’s an extra step to maintenance to get in to check torque or tension or to check [air pressure],” he says.
Proper torque is key to ensure a lasting and secure installation.
Tire pressure, galvanic corrosion
Even tire pressure is a factor when it comes to protecting the wheels themselves, because tires act as dampers between road bumps and wheels, Uzarek says. “If you run under-inflated, you may have less of a damping effect, and you may harm the rim more.”
Under-inflation could also put the wheel or its valve more at risk of damage if a curb is hit, especially when it comes to low-profile tires, Thomas says.
Aluminum wheels, meanwhile, are better able to dissipate heat than under-inflated tires and other wheel-end components like brakes, he adds.
To combine the cheaper price of steel wheels with the shiny look of aluminum, some fleets will use steel wheels on the inside of a dual assembly and aluminum on the outside. It’s not forbidden, but maintenance teams need to keep in mind that corrosion from the steel part of the assembly can travel to the aluminum wheel and cause the two to seize together, Uzarek says.
Wheel guards – discs inserted between the wheels in a dual assembly — can prevent this. “They are very useful between steel and aluminum wheels and between the brake drum and inner dual, where galvanic corrosion will occur,” he says.
Alcoa’s Thomas thinks it’s best to avoid anything that sits between the wheels. “What we do recommend is keep that mounting surface clean. We did produce wheel guards many, many years ago and we got out of the business. We realized it was causing more hassle than benefit.”
When it comes to aesthetics, it might be best to avoid acidic cleaning products away from the aluminum designs.
“First we need to understand if the wheel is coated. If it’s coated, both us and our competitors recommend using a mild soap and water,” Uzarek says.
“If you look under a tractor or a trailer that has been acid washed many times, everything starts to disintegrate,” Thomas says. “Our wheels don’t like it either.”