It's not often that I take a stand on something, because my everyday job precludes me from saying anything too controversial. But I'm seeing more and more devices being used to identify potential wheel-off incidents. Some of these particular devices are now evolving into some interesting concepts on the original theme. Since I'm not sure how to accurately describe the entire category, I'm going to start by referring to the colored plastic arrows that warn a driver and/or maintenance person when a lug nut has “backed off.”
As I see it, the concept of the arrow is that when a nut and stud lose all of their tension, centrifugal force will cause the nut to become loose. If all of the plastic arrows are aligned in the same direction immediately following installation, then any loose nuts will be easy to find because the “points” will not line up with the other arrows. It sounds so simple and obvious that you would think every truck should have them. The fact is, the arrows cannot identify a nut and stud that has lost tension to the point where it cannot support the weight of the vehicle and its cargo even though it still appears to be tight. Nor can the arrows identify a substandard wheel stud that is incapable of producing sufficient clamp load with the correct amount of torque. And if the nuts and studs have been overtorqued (as many have been), those little colored arrows will all point in the same direction like soldiers in formation.
I personally believe that most commercial wheel and rim fasteners are overtorqued, however, I don't have any data to support this. Since the “tighter is better” mentality appears to be at least a decade away from changing, I estimate there are literally millions of studs that are either approaching or passed the yield point where permanent damage has occurred. These fasteners can be difficult to spot because they are stretched to the point where they are unable to maintain sufficient bolt tension after installation but are still intact. Checking the torque after a few miles might identify a fatigued stud, but it's unlikely that the little colored arrow will ever move.
Like the misdirected and irresponsible marketing approaches to nitrogen inflation that suggest a tire need not be checked after being inflated with (almost) pure nitrogen, the little colored arrows can provide the same sense of false security. And like the legitimate benefits of nitrogen inflation, I must acknowledge that you will find an occasional lug nut that begins to loosen and back off (if the driver bothers to check). But in the real world, little plastic arrows are not going to prevent wheel-offs any more than nitrogen inflation will prevent roadside tire debris. Both may help people sleep better at night, but neither can account for all of the factors that lead to loose wheels and failed tires.
The only way to prevent a wheel-off is to properly install the components with the correct amount of torque and then check the torque at periodic intervals. If the little plastic arrows are incorporated into a quality wheel torque program, then there's no harm in some additional protection. But if fleets are going to rely on those arrows to identify a potential wheel-off without taking any steps to ensure they were installed correctly in the first place, then I know a guy with a line on some dashboard hula girls that can spot an unbalanced tire just by the way they shake.
Kevin Rohlwing can be reached at [email protected]