When it comes to truck tire and wheel service, there are many steps and procedures that must be followed. Some of them are required by federal Occupational Safety and Health Administration (OSHA) regulations, some are considered manufacturer guidelines and others are recognized as best practices by the industry.
Regardless of their origin, technicians must know and understand them so they do not unintentionally create a problem where one did not previously exist.
In the area of wheel and rim installation, the primary place where lubricants play a critical role in the safety and performance of today’s truck tire and wheel assemblies is the affect they have on torque and clamping force. On certain wheel systems, the use of the proper lubricant will definitely have a positive impact on the life and performance of the assembly, while the use of an improper lubricant can have serious consequences.
In order to help technicians understand these guidelines and the relationship between torque and clamping force, the Tire Industry Association (TIA) has developed a Fleet Tire Service OSHA Compliance Training Program that outlines the instances where lubricants are required, as well as the types of lubricants that must be used.
First of all, technicians must know the requirements for each type of wheel and rim system used in North America. For example, the demountable rim, or Dayton system, is characterized by open-center rims that fit over a cast spoke hub. The rims are secured to the end of the axle by a series of clamps (or wedges) and nuts that must be equally tightened in order for them to run true.
Since the demountable rim system relies on friction to keep the rims from spinning on the cast spoke wheels, there cannot be any lubricants on the mating surfaces. Technicians may think they’re doing themselves a favor by applying a thin film of anti-corrosive compound to limit the effects of corrosion, but in reality, they are reducing the amount of clamping force that keeps the rims from spinning.
On the other hand, the torque specifications for these rims are dry, so the application of a lubricant on the threads will create excessive clamping force at the required torque which contributes to damaged and worn components.
Stud-piloted wheels, also known as Budd wheels, are another system where the torque specifications are dry – for the most part. These wheels can be identified by a series of inner and outer cap nuts on dual wheels that have left-hand threads on the left side of the vehicle and right-hand threads on the right side of the vehicle.
Unfortunately, it is not uncommon for the inner and outer cap nuts to “freeze” together during the removal process. This can lead to a number of problems, the most serious of which is forcing the studs into the hub or drum.
Technicians surmised that by coating the threads of the cap nuts with an anti-corrosive compound that includes rust-inhibiting properties, the inners and outers would not freeze together and they were right. So the application of “never-seize” became commonplace when installing these wheels.
What these technicians failed to realize was that most stud-pilot torque specifications are dry. When lubricated values are given, the approved lubricant is standard 30-weight motor oil.
Additionally, the lubricated specs call for lower torque values to account for the loss of friction. When technicians substitute the recommended lubricant (motor oil) for an anti-seize compound, the relationship between torque and clamping force is changed.
It’s also important to note that there are several reasons why inner and outer cap nuts freeze together and the presence of substances like “never-seize” may have unintended consequences.
For example, excessive corrosion on the threads may cause them to stick together, as will threads that are damaged or severely worn. So in reality, the application of anti-seize compounds keep bad fasteners in service longer.
For those who are concerned with the liability associated with wheel installation, the evidence left behind is an easy “smoking gun” for the plaintiff’s attorney looking for the cause of a wheel-off accident. None of the wheel, hub or fastener manufacturers recommend the use of any lubricant on a stud-piloted wheel system other than oil, so residue left by anti-seize compounds becomes an easy scapegoat for even the most inexperienced attorney.
On the other hand, the use of oil on a hub-piloted installation is crucial to the torque and clamping force relationship.
While there may be some lack of consensus on the use of lubricants for stud-piloted wheel systems, all of the manufacturers and industry organizations agree that standard 30-weight motor oil must be applied to the studs and flange nuts before installing a hub-piloted wheel. In fact, when oil is not applied, or anti-seize is used as a substitute, the recommended torque can result in up to a 50 percent loss of clamping force.
So, fleets that are diligent in their efforts to ensure that every hub-piloted wheel is installed with the proper torque could be creating additional problems if the studs and flange nuts are not properly lubricated. It becomes a perfect example of the phrase: “false sense of security.”
TIA’s Fleet Tire Service OSHA Compliance Training Program details the relationship between torque and clamping force on the three main wheel and rim systems used in North America.
The hub-piloted fastener tests alone are usually enough to convince even the most experienced technician that there might be a better way. If that doesn’t do it, then the footage of a wheel-off striking a parked car makes a believer out of most students.
Truck rim and wheel systems are a lot more than just nuts and bolts. Without a firm understanding of how these systems work and the role that a lubricant plays in creating clamping force, technicians are simply guessing every time they install a wheel or rim.
For more information on how the training program can protect your fleet from a costly wheel-off accident, contact TIA director of training Chris Marnett by phone at 800-876-8372, ext. 106, or by e-mail at firstname.lastname@example.org.