One First Hand Experience
A veteran long haul truck driver we spoke with related this experience:
“I had loaded 40,000 pounds of rice in bags into the trailer and set off for Toronto. Rice is very easy to haul as it stacks low and heavy in the trailer and resists movement in transit. I could fly through the curves.
“In Alabama my trip stalled due to a flat tire on the left rear trailer axle. I was lucky to find an open shop that quickly repaired the tire and sent me on my way. The trip was uneventful until I stopped at our small fleet yard in Southern Ontario, Canada.
“At that point a relief driver had been booked to take the load the rest of the way to Toronto, a distance of about 200 miles. Unfortunately the driver had a medical emergency and the dispatcher arrived to greet me and inform me that I was to carry on to Toronto.
“I began to perform a pre-trip inspection and found a freely spinning wheel stud on the tire that had been fixed in Alabama. The stud was obviously broken so I informed dispatch that I could not proceed. But being a driver for a very small fleet of only 3 tractor trailers and needing the job I was coerced by dispatch into carrying on to the delivery point with the remaining 9 studs holding firmly.
“I Should Have Refused the Trip”
“I have always regretted not walking off the job there and then. I should have refused the trip. Heading off for Toronto I put 90 miles behind me when I noticed a wheel assembly passing me on the left. The buggers seem to really speed away when freed. That wheel and tire crossed the median and westbound cars started dodging it head on as it continued to roll.
“The inner wheel also came free and passed under the trailer, got ahead of me, went down into a small ditch and came out the other side flying about 20 feet in the air and over a fence into a cornfield before I got the rig pulled over. All 10 studs from that assembly had broken as a result of over-torquing of all the studs by attaching with an impact wrench after the flat repair.
“Those of us on the highway that day were incredibly lucky not to have been injured or killed. About a month later I was travelling north on I-75 in Florida when a truck ahead of me lost a wheel. It crossed the median and hit a small southbound car head on. The lady driver was killed instantly, the car totaled.”
Wheel Runoffs can be Deadly
Truck wheel runoffs still occur today but with much less frequency and every bit as much deadly force. Laws are in place now to assess hefty penalties to the driver and fleet in the event of a runoff. Daily inspections must include looking for signs of loose lug nuts such as rust around a stud or a leaking wheel seal which could indicate a potential hub failure.
Causes of Wheel Runoffs
Most wheel runoffs are caused by under-torqueing or over-torquing the lug nuts. Wheel mating surfaces must be cleaned of dirt and debris before attaching. Some wheel assembly runoffs are caused by hub failures due to lack of lubrication, or under-torqueing or over-torquing the axle nut that holds the wheel bearing in place.
The ideal torque specification for truck wheel lug nuts is 400 foot-pounds and is measured using a hand operated torque wrench. Most truck shops nowadays use the torque wrench to accurately fasten truck wheels.
But some are still using impact wrenches that can apply torque up to 2,000 foot pounds, dangerously over-torquing the lug nuts. This has the effect of stretching the wheel studs and sets up a vibration when driving on the highway. That vibration ultimately breaks the wheel studs and results in a wheel runoff.
Preventing Wheel Runoffs
To avoid this type of runoff, instruct your drivers to never allow an impact wrench to be used to tighten wheels after wheel off repair. Have them always insist on tightening of the lug nuts with a hand torque wrench. In avoiding liability most truck repair shops will recommend hand re-checking the torque after the truck has covered 60 miles, just to be sure.
During preventive maintenance inspections, require your technicians to always check all wheels for proper tightness with a torque wrench and adjust if necessary. This small step, though somewhat time consuming, can prevent catastrophic wheel runoffs and even save lives.
Always inspect for signs of leaking axle seals that could lead to bearing failure and a wheel assembly runoff due to hub failure. This can result in a 500 pound missile being launched under powerful force into opposing traffic. Take a little time for prevention, for everyone’s sake.
Bottom Line: Never let a truck leave your yard with a single broken wheel stud or any wheel mounting in doubt. You just never know.