What Are Those Plastic Strips Hanging Off Truck Wheels?

Photo illustration by Justin Dodd; Photo by John Keeble/Getty Images

Trucks are the mobile mystery machines of the road, dangling tantalizing clues about their capabilities and operations that seem strange to four-door sedan drivers. We’ve previously explored why they have spikes on their tires, why they warn of making wide right (but not left) turns, and why there’s a “spinny thing” on top of some delivery vehicles.

Another puzzling feature: Why some trucks have plastic strips dangling from the lug nuts of some of their wheels.

According to Jalopnik, the strips are a highly economical and effective way of figuring out when a truck driver has a problem with the wheel. The strips, which are simply placed under a tightened lug nut, are a signal the wheel is in motion.

If the truck is on the road, why wouldn’t it be? Several reasons. A truck’s air braking system may lock up or fail to engage after stopping and starting the engine. Worn-out or rusted braking components can also be to blame.

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By putting a wheel rotation indicator on the wheel, the driver can clearly see whether the wheel is operating properly. It’s also easy to spot when checking the wheels from a rearview mirror, as they typically stick out 2 inches or so from the rim.

Obviously, you won’t find the strips colored black. They’re usually orange or yellow for easy visibility. They’re sold under the brand name Skiddd as well as others. And while they’re ostensibly just a strip of plastic, they can help prevent damage or accidents. Think of it as the lowest-tech safety monitoring system on the road today.

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