Remember the Kenny Rogers song, “It's a Fine Time To leave Me Lucille”? It's a crying-in-your-beer country tune lamenting a wife's departure. NASCAR legend Darrell Waltrip is said to have borrowed this tune one time for a lament of his own: “You picked a fine time to leave me, loose wheel.”
Wheels, of course, are the essential link between the truck chassis and road surface. So keeping them firmly attached is a key maintenance issue.
The Technology & Maintenance Council (TMC) has just finished writing a new Recommended Practice (RP) 237, “Retorquing Guidelines for Disc Wheels.” Several key points from this new RP and the discussions leading to its publication are noteworthy:
All tire/wheel assemblies, once installed, go through a “settling in” period during which some clamping load is lost.
All disc wheel suppliers to the North American market, including manufacturers of steel and aluminum wheels, recommend retorquing wheels after a run-in period.
While a long-standing industry consensus recommends retorquing after 50-100 miles and again at 10,000 miles, the new RP provides an alternative for fleet-specific needs, allowing retorque intervals to be based on individual fleet equipment, service conditions, and maintenance issues. Procedures for establishing these fleet-specific intervals are detailed in the new RP.
The specific type of torque measurement tools and procedures used can affect torque readings and, therefore, accuracy.
Quality and physical condition of wheel-attaching hardware can be critical to torque and thus clamping load retention.
These new retorquing guidelines should be used in conjunction with the wheel installation procedures detailed in RP 222, “User's Guide To Wheels And Rims,” to address a complete wheel nut torque maintenance program. More information and copies of these RP's can be obtained online at www.tmc.truckline.com, or by calling TMC directly at (703) 838-1763.
Two key features of the new RP are worthy of special attention and application to your fleet. First, the primary factors affecting torque retention are enumerated and discussed. Attention to corrosion, proper fastener lubrication, and paint film thickness (on steel wheels) are three of the items specially noted. Personnel training, truck washing frequency and chemical cleaner use, wheel refinish program monitoring, and shop supplies (fastener lubrication) are some of the related areas that can significantly affect wheel torque retention.
Secondly, procedures to establish retorque intervals that meet the specific needs of your fleet, based on your equipment and vocational service conditions, are detailed in RP 237. Wheel end maintenance requirements can vary significantly, and the new RP addresses this so you can methodically arrive at programs to address your fleet's needs. It's noteworthy, for example, that cornering that is especially frequent and/or severe, as well as other side-force inputs could speed up the new wheel settling-in process.
If you have questions or concerns about wheel torque retention, technical reps from wheel manufacturers are excellent sources of information. Accuride Corp. (1-800-869-2275), Alcoa Wheel Products (1-888-999-6310), and others are readily accessible.
As with many maintenance issues, once you get your hands on the right information, most of the conflicting advice and problems disappear.