Dealing With Nuts
Solve Frozen Nut Caps With Low-Tech Techniques
We’ve all heard the speculations and read the stories: Computer chips in tires with handheld readers for commercial tire service technicians are just around the corner. Every truck will need a laptop and Internet access in-cab by 2010. The information age has finally arrived, and tire service must adapt to a world of microchips and modems.
Won’t that be fun?
I can see the benefits of Internet access, especially if it means we have global satellite positioning of every vehicle on earth. As a tire service technician, I’d love to type in a disabled vehicle’s ID number and get an exact location with continuous traffic updates to ensure the fastest route.
But before we computerize a tire/wheel assembly and have complete in-vehicle GPS, the industry needs to address a low-tech issue, one that has tormented commercial tire service technicians for decades.
There must be at least one effective method for preventing and separating frozen inner and outer cap nuts on stud-piloted wheels.
Technicians don’t expect cap nut installation procedures to completely eliminate the problem, because they know it’s not possible. They aren’t asking for a device that uses electromagnetic forces to turn the cap nuts without the use of an impact wrench because they know it would cost too much.
But if they could find a way to reduce the likelihood of frozen cap nuts without having to spend a lot of time or money, they would do it immediately.
People think the most common cure for frozen inner and outer cap nuts is the use of anti-seize compound on the threads. While it appears to solve the problem under certain circumstances, using such products violates every manufacturer guideline for wheel system lubrication. According to engineers, the only acceptable thread lubricant for any wheel system is 30-weight oil on hub-piloted studs. Most published installation procedures for stud-piloted wheels require a dry torque setting on the cap nuts with no lubrication. Alcoa allows 30-weight oil on inner cap nuts, but the final torque is considerably less than the standard 475-ft. lbs.
So what happens when a technician applies anti-seize compound to the threads of an inner cap nut?
First, any debris or loose dirt on the threads is transferred to the brush and eventually into the can of anti-seize compound. Just imagine a nice jar of creamy peanut butter slowly turning into a jar of really chunky peanut butter. Those chunks of accumulated debris cause future problems.
Second, since torque is a measure of twisting force that results in clamping force, a lubricant causes more twisting which creates more force. Broken studs and nuts shouldn’t be a mystery with the presence of a lubricant and the absence of a torque wrench.
Finally, the threads are going to wear faster and deform at an accelerated rate when they are over-torqued.
Follow Simple Steps
Preventing frozen inner and outer cap nuts is easy if a few simple rules are followed:
- Always clean and carefully inspect the threads on both studs and nuts
- Replace any inner or outer cap nuts that have damaged or worn threads
- Never remove an outer cap nut without retightening the inner cap nut; even if it doesn’t appear to move, it has
- Use no lubricants other than those advised by the manufacturer and applied in the fashion recommended
- Make sure the inner and outer cap nuts have the same amount of torque – use a torque wrench
On the other hand, someone has to separate and dispose of the frozen inner and outer cap nuts after the damage has been done. Technicians have turned to porkchops for years, and even modified them to prevent broken toes and pinched fingers. Various methods for keeping the porkchop in place have also been used, but, unfortunately, separating cap nuts on aluminum wheels usually resulted in scratches, gouges and upset drivers. While most porkchop procedures were effective, none of them were just right. Until now.
New Chop Option
While neither ITRA or this magazine do not endorse any product, tool or process (and never will), our job is to report technological advances to our respective readers and members to make sure they are on the cutting edge of technology. If something saves time and money or helps prevent injuries, it’s our duty to let you know. One such item is the TX200 from Ken-Tool, which in my mind is the "perfect" porkchop.
Welding an inner cap to an old style porkchop damages the center or bolthole. Using a pair of locking pliers is effective but clumsy. The old style porkchop scratched aluminum wheels no matter how you used it or how careful you intended to be.
But this new style porkchop fits the contour of the center hole so it doesn’t bang around and damage the wheel. And it doesn’t slip and get wedged between the nut and the disc. Plus, it has no moving parts and appears to be quite durable. Simple is always best, in my opinion.
Up to the Technician
Frozen inner and outer cap nuts don’t have to be a problem. But they will never go away, either. Drivers still tend to think, "It’s my truck, and I can do anything I want." Just remember that it is the tire service technician who is still considered the expert regardless of who owns the vehicle.
Any stud-piloted wheel system tainted with anti-seize compounds is a law-suit waiting to happen. If stud-piloted wheels come off the vehicle for any reason and cause damage or injury, the dealer who put them back into service with lubricated threads will need a lawyer.
Careful fastener and wheel mating surface inspection is also necessary with every wheel system, so technicians should be trained to recognize components that need to be replaced – and make sure they replace them.
Kevin Rohlwing is director of training for the International Tire & Rubber Association (ITRA), and this article originally appeared in ITRA’s Commercial Tire Service publication.