Learn why wheel-offs can occur and what the solution is to this dangerous and costly problem.
Episode 94: In this episode, Dave Walters, Doug Mason, and Mike Yagley, co-hosts of the Behind The Wheels Podcast, tell the story of a major fleet who was having wheel-off events. They also explain what the common causes of wheel-offs are and what solutions they recommend to solve this dangerous and costly problem.
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When you have a wheel-off situation it is a catastrophic failure that puts the public and the driver at risk of serious injury or even death. Additionally, the fleet has to deal with costly repairs, potential fines, and other forms of financial liability. This is something to be avoided. But, why do wheel-offs occur?
There are several reasons why a wheel-off occurs but the cause isn’t always obvious as was the case with a commercial fleet in 2011. “It was a major waste removal company in the USA, and they were having wheel-offs. They couldn’t figure out why it was happening so they asked a group of four of us to try and solve this,” explained Dave Walters.
When this team of wheel specialists started trying to identify the cause of the wheel-offs and develop a solution they learned some valuable lessons that would not only help the waste removal fleet but also become very valuable information for the entire industry.
The Importance of Proper Torquing
One of the main lessons learned was that the wheel stud acts like a spring. When you torque a nut, you stretch that stud out slightly to hold the wheel in place. The wheel stud has an elastic zone that it will bounce back from as long as you don’t overt-torque the wheel stud. The plastic zone however is when you over torque the wheel stud, and it won’t go back and function properly.
“When you are torquing down the nut itself, you are creating force and stretching out that wheel stud. If you over torque and stretch the stud, it will not go back in shape,” said Doug Mason.
Another lesson learned was the importance of knowing the specifications for each application. The “good and tight” method isn’t an accurate and safe way to torque lug nuts. Using the proper torque and checking the wheel within a 50 – 100 miles is an important step to ensuring that wheel-offs don’t occur. Even making sure the wheel stud is clean before torquing can contribute to preventing wheel-offs.
Rolled Vs. Cut Threads
Manufacturing a wheel stud with rolled threads involves a process of reshaping the material with a mechanical process to form the thread. A cut thread involves a subtractive machining process where raw material is removed forming the thread.
“When you’re machining a cut threat, you are actually cutting and removing material. When you do a roll thread, you don’t remove material in that case,” explained Mason.
Rolled threads make a stronger wheel stud. The process costs more to manufacture but saves money over-time because they last longer and are safer. The thread doesn’t fatigue as quickly and will withstand the demands of commercial trucking.
Informing the Trucking Industry
It was very important to provide this information to the entire trucking industry. Not only was the fleet that was having the problem able to benefit but by providing the lessons learned to the entire industry many fleets were able to avoid wheel-off situations. Now looking back over ten years later we can see the positive impact the work done by Dave Walters and the other members of the team has had industry-wide.
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