"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."
Alcoa's Walters sees most problems pop up after brake jobs, when technicians don't take proper care in seating the brake drum. Corrosion and debris must be cleared away, and the heavy drum must be placed correctly. Walters suggests a simple solution: "If you take the actual nuts and run the drum up to where you can see it move in and seat on that pilot, then lock your brakes, that's not going anywhere."
Walters also sees problems with technicians seating the wheels. Technicians will sometimes lean against wheels and snug the first nut up and run it in too far. "He'll get the wheels cocked--and there's only about twenty-thousandths clearance between those pilot pads and the wheels themselves--and if he runs one of those nuts in too much, he gets the wheel actually cocked on the pilot pad," Walters warns. "As much as he thinks that he can draw those in with that big one-inch gun, once you get that wheel cocked, you're not going to get them drawn in completely snug again."
The fact that there is currently no standard in North America for the proper mounting and attachment of truck tires upsets Bruce Boyce.
"What's sad is, we go to school for four or five years to get a certificate so we can pull an engine apart and put it back together, and people aren't allowed to touch it, but when it comes to wheel ends, anyone with a pair of coveralls can take it off and put that wheel back on," says Boyce, former fleet maintenance professional and now founder/CEO of Manufacturer Direct Ltd. "It should be mandated that if you're dealing with a wheel, you should be going through a certain legislated training."
Boyce is on a crusade to eliminate "wheel-offs," and his company makes a device that may do just that; the Saf-T-Loc both locks down heavy truck wheel nuts and flags the driver and technician if a nut is coming loose.
According to Boyce, fleets are spending too much money on retorquing, while not addressing the real issues. He, too, stresses that fleet technicians should be pulling drums and cleaning the brake dust and rust between the drum and the wheel.
"In that wheel you'll get water from the road, because most fleets are running without backing covers now to dissipate the heat better, and they feel that anything that gets back there is held in by the dust cover," he explains.
But contamination isn't Boyce's biggest issue. He saves his strongest criticism for the technicians he feels are torquing wheels improperly in the first place.
"The biggest hypocritical thing about retorquing wheels is, putting a torque wrench on the stud until it goes click will tell you that it's 500 ft-lbs, but it won't tell you if it's really 600, 700, 800 or 900!" he says. "That's the bigger damage is the stretching of the stud, because the tire guy went crazy."
Can your technicians tell if a stud has been stretched by a crazy tire guy? Boyce's recommendation is that every tech who deals with wheels should invest in a simple thread-pitch gauge. "The people who are damaging the studs are the tire people on the road," he says. "Most of them don't own a torque wrench, and they're torquing that wheel nut 'til the gun stops. They're stretching the studs when they do that. With a thread pitch gauge, any time you have the wheel off, you measure the stud with the gauge and it'll tell you if that stud is stretching."
Fournier, at least, is listening. Loblaws trains its tire vendor's staff and its in-house technicians to be on the lookout for stretched studs any time a wheel comes off a truck or trailer.
"We have it incorporated into every one of our drive services, every time a wheel comes off they're supposed to inspect them," he explains. "You take a new stud, you lay it up against the threads, and you can see, instantly, with light underneath, if there's any deformation happening in the thread area between the rims and the brake drum."
The strategy seems to be working: Fournier uses Boyce's Saf-T-Loc product, and three months ago Loblaws started replacing all wheel studs after five years or 500,000 miles, and today their wheel-off problem is nonexistent.
For more on preventing wheel-offs through proper torquing, go to www.fleetmag.com