Over the last several years the Tire & Wheel (S.2) Study Group of the Technology and
Maintenance Council (TMC) has developed Recommended Practices to prevent
wheels from coming off vehicles while they roll down the road. Unfortunately,
wheel-offs still happen more frequently than any fleet likes.
There are two primary causes of wheel separations: wheel bearing failures and
improper wheel installation.
Wheel bearing failures occur when the axle end bearings freeze up and the hub stops
turning due to lack of lubricant in the hub oil reservoir. When this occurs, the hub,
drum, and both dual wheels experience extreme overheating and separate from the
vehicle as one unit.
Wheels must be installed properly to achieve a tight “sandwich” of wheel end components or after the wheel system “settles in” from running a few miles, the wheels will become loose.
The Tire Industry Association (TIA) has created an easy to remember system for ensuring technicians perform all the steps necessary for achieving the proper clamp load when installing wheels. It is called the “RIST” procedure:
- R stands for removing debris from the mating surfaces.
- I stands for inspecting components and getting rid of ones that are not serviceable.
- S stands for snugging the lug nuts in a star pattern.
- T stands for torquing the lug nuts to specification. Achieving the specified torque can only be confirmed with a calibrated torque wrench.
Finally, the torque on wheel nuts must be checked 5-100 miles after a tire change. This torque check is specified by wheel manufacturers as well as TMC which has included this requirement in its RP222 User’s Guide to Wheels and Rims. This practice ensures you find loose wheels that develop after wheel end systems “settle in” and prevents wheel-offs from occurring.
However, knowing that tires have been changed and wheel nut torque should be checked when the vehicle gets to its next destination has always been the problem that keeps fleets from checking nut torque. However, TireVigil™ Cloud knows when tire/wheel assemblies have been changed and automatically sends a reminder to the right location that wheel nut torque should be checked. It also monitors tire temperature and alerts you to axle ends that are overheating possibly due to frozen wheel bearings and thereby prevents wheel separations due to both bearings and improper wheel installation procedures.
If you are concerned about wheel-offs which are extremely costly in lives, vehicle and property damage, and lawsuits, you should see what TireVigil Cloud can do for your fleet.