uncil (TMC) has an excellent publication titled "User’s Guide to Wheels and Rims" which is a compilation of the knowledge and experience of top industry suppliers and fleet maintenance personnel. The installation, inspection, and maintenance procedures for wheels, rims, and fastener components in this TMC Recommended Practice are readily available (phone 703-838-1763) and should be required reading for all truck tire/wheel service technicians.
The trucking industry strongly encourages drivers to conduct routine visual inspection of wheels, and certainly wheels should be carefully inspected during regular maintenance service. But, what better opportunity to perform a more detailed inspection of both interior and exterior wheel surfaces than at tire change time!
Seize The Opportunities
Many fleet operators have opted to contract out tire service and retread operations to commercial tire specialists. Taking advantage of this factor and adding in thorough, standardized and high quality wheel inspection and refinishing operation gives commercial tire dealers an entirely new profit center for their business.
One additional plus from a safety standpoint such a consistent system allows suspect wheels to be culled out based on a "clean metal" inspection ®“ not a substitute for normal maintenance, but certainly a plus. Proper refinishing also facilitates concentric bead seating and air retention, enhancing both the on-road performance and lifecycle value of the fleet’s tires.
The Finish Is In The Details
Like many good maintenance practices, wheel refurbishing isn’t rocket science, but does require consistent attention to detail and quality control.
About 15 years ago, International Marketing Inc. (IMI), followed by several other suppliers, introduced modular wheel refinishing systems to the industry. Since these systems are fairly large, most have been installed in commercial tire dealer and retread locations.
For steel wheels, there are three basic elements of a good program cleaning, inspection, and surface refinishing. There have been significant advances in wheel refinishing recently.
The upside is that the more durable paint formulations and premium powder coat finishes on new wheels deliver a high gloss look and extended wheel life. The downside is that these new coatings are difficult to remove when the time comes to inspect and repaint. And some of the methods being used to strip these wheels are, in fact, causing unnecessary and potentially dangerous damage to them.
Ups and Downs of New Finishes
Currently, about 10% of new disc wheels for Class 8 trucks are shipped with powder coated finishes. Since paint removal tends to be the bottleneck in any refinishing operation, some refinishers have approached the problem by using larger, more aggressive shot as the blasting medium used to strip the wheels. This gets the old finish off quickly, but can cause unnecessary surface etching or roughness.
Such heavily scarred surfaces make accurate visual inspections more difficult, and require considerably more paint to achieve the desired smooth, high gloss finish.
Control of paint thickness is extremely important, especially in and around bolt holes, valve stem holes, and on all wheel mating surfaces. Overly thick paint application can cause unnecessary and potentially dangerous ®“ problems maintaining wheel-truck attachment, retention of air, and even proper bead seating.
Around bolt holes and wheel mating surfaces, excess paint can compress after initial torquing, resulting in loss of clamping force a precursor of loose wheels. According to Bill Noll, vice president of product technology and development for Accuride, the industry recommends a maximum paint thickness of 3.5 mils.
Excessive coating around valve stem holes can cause improper valve stem seating, the recipe for continuous air retention problems.
New Systems Improve Results
Research and development in the wheel refinishing area appears ready to raise the bar with a new generation of machinery that allows use of smaller, blended shot size to reduce cycle times and strip the old finish more consistently. This is achieved with new types of blasting processes, shot delivery systems, and other machine modifications.
Combine this with advances made in liquid paint material and process technology and smooth, glossy and safer ®“ refinished wheels may become the norm. The new units will also offer the option of premium powder coating.
Regardless of which coating system is chosen, technology advances should require less coating material. Some of the new refinishing systems, such as IMI’s Series 2010 system, also offer infrared curing ovens to obtain faster, contamination-free drying.
This may set the stage for fleets and other users to specify from a larger variety of refinish options and colors, and set new standards for such things as paint thickness, gloss, and adherence to other wheel finish quality variables.
Even with these machine advances, operator training and overall quality control remains important. Truck operators should, as always, look to their vendors for assurance that these issues are properly addressed.
It’s no secret that radial truck tire technology has taken major leaps forward in recent years, maybe now it’s time for the wheels to "shine" a little.