"Industry consensus has long recommended that wheel systems be retorqued between 50-100 miles after tire and wheel assembly installation on a vehicle and at 10,000 mile intervals after that. Some fleets reportedly do not follow this recommendation because of logistical concerns."
So says the Technology & Maintenance Council's (TMC) Recommended Practice 237, "RETORQUING GUIDELINES FOR DISC WHEELS." In those two sentences lies a conundrum that has yet to be addressed by the fleet maintenance community: if retorquing wheels after 50 to 100 miles of mounting is an "industry consensus," then why do "logistical concerns" prevent "some fleets" from following the recommendation?
"The issue that I have with wheel retorques is trying to manage them, to see that they get done," says Rick Fournier, director of maintenance for the Western Canada unit of the Loblaws grocery chain. "You can put a set of wheels on a unit with the suggestion that it should be retorqued within 100 miles. Trying to get a driver to stop en route (for a retorque) in that time frame and verify that he actually did stop is very difficult to manage."
Fournier's approach? Use the right tools, and make sure the wheel is torqued correctly in the first place, and you'll not only eliminate the need to retorque but eliminate the risk of wheel-offs as well.
RECOMMENDED PRACTICE 237
TMC Recommended Practice (RP) is actually an effort to provide fleet maintenance managers like Fournier with practical alternatives to the 100-mile retorque, according to Dave Walters, manager of warranty & field service group, for Alcoa Wheel Products, and the leader of the team that wrote RP 237.
"What we found out from our data was, if your guys put these wheels on correctly the first time, and torque them down, we basically we lost no torque whatsoever over the life of some of these wheels ends, and we were putting on tremendous amounts of miles," Walters says. "If you clean the mounting faces of the wheels and the drums, and you put the wheels on right, and you torque them to a specific spec', and you have the studs basically in good shape, your system is in control."
The RP gives fleets two alternatives to retorquing after 100 miles on the road. The first option is to take the loaded vehicle out for a five-mile test run, then return to the shop and test the torque. "What we found even from that in our data was that they never lost torque again," Walters reports.
The second option is to regularly check the torque on 30 wheel nuts in your fleet, completely at random. According to Walters, 30 is a statistically-sound sample that will show whether your fleet has a retorquing problem.
"Say for example, you have 100 trucks at one location," he suggests. "You think that you've got your system totally under control, that you're putting everything on right, you're cleaning everything, you're torquing everything, you're keeping your studs in good shape--you should check (30 nuts) once a quarter, that's what we recommend."
DOING IT RIGHT
For some fleet maintenance managers, the issue of whether to retorque or not goes beyond questions of practicality and added costs; it goes straight to the heart of maintenance practices in the shop.
"If there is an issue with the wheels coming loose, my first question is, 'Why did they come loose?'" says Fournier. "They shouldn't come loose. When was the last time you had to retorque crankshaft main bearings on that engine when you put it together? You don't. So why is it so much different on a wheel, where we have people saying you have to retorque it? Well, it's to cover up sloppy workmanship. They either didn't clean the components properly, didn't inspect the components properly, or they didn't identify what they were supposed to be doing and do their job correctly in some form or fashion."
"The big problem is bad maintenance," says fellow Canadian Vernon Seeley, specification manager and technical advisor for Sunbury Transport in New Brunswick. "People don't inspect the pitch on their studs. They need to be trained to identify corrosion of the stud near the hub, or to see if the hub's not on straight."