I’ve had a front row seat for all of the major changes to the truck wheel installation process over the past three decades. By combining “good-and-tight” with anti-seize, technicians thought they had the solution for stud pilot wheel systems in the 1980s. When hub-piloted wheels started showing up in the ’90s, the good-and-tight process remained, but the cans of anti-seize went back in the cabinet because there were no frozen inner and outer cap nuts. For most people, torqued meant tight so everyone was happy.
Things started changing around the turn of the century as commercial tire service providers and fleets began to recognize the importance of precision when installing disc wheels and rims. With hub-pilot systems dominating the market, people started paying more attention to the actual torque specifications. At first, the solution appeared to be torque-limited extensions (torque sticks) because they wouldn’t create a lot of resistance in the shop. Unfortunately for technicians, they were proven to be inconsistent, so the industry had to adopt torque wrenches as the tools for wheel installation.
Tools aside, the spec of 450 to 500 ft.-lbs. for hub-pilot and stud-pilot wheels had universal acceptance. In order to account for the natural variation in torque wrenches, the target of 475 ft.-lbs. was easy to remember for technicians. Most of the vehicles on the road have disc wheel systems as opposed to demountable rims, so the tools could be set at 475 ft.-lbs. in the morning and left there until the end of the day. The simplicity was something to behold— and apparently, short-lived.
One of the unintended consequences of the 475 ft.-lbs. spec is the reliance on checking the torque within the first 50 to 100 mi. after installation. Dual wheels can settle as they flex, which may result in the loss of bolt tension. The only way to determine if the clamping force has been reduced is to check the torque, which means the fasteners need to be checked shortly after the wheels are serviced. Tests have shown that when technicians pay close attention to the details of cleaning, lubricating (on hub-pilot wheels), tightening and torquing, the torque check is not necessary. However, the lack of consistency in the field makes torque checks a harsh reality for most of the industry.
That reality has led to fleets asking for different torque specs from their wheel suppliers partly because they are unwilling to follow the torque check recommendations. And while it seems like higher torque settings are a logical solution, it’s creating an unprecedented level of confusion for the commercial tire service industry. What used to be a simple process of torquing every disc wheel to 475 ft.-lbs. has become a literal soup of different specifications. Fleets are telling their service providers to raise the torque as high as 650 ft.-lbs., which puts the tire dealers in a tough spot.
When fleets are unable to produce written documentation that their wheel supplier has approved a higher torque setting, the only option is to stick with the published torque specifications. Standard of care requirements dictate that installers follow industry guidelines at all times, so 475 ft.-lbs. is the only acceptable target in most cases. But the growing number of fleets with a different spec are taking a clear picture and making it muddier by the day.
The most common question among commercial tire dealers is why won’t the wheel companies just approve a higher torque setting for hub-pilot wheels? When the industry has different sets of rules for the same components, it’s only a matter of time before the soup goes bad.
Kevin Rohlwing can be reached at [email protected]
