What are the plastic arrows on the truck wheel nuts for?

Typical storage questions from the back seat are exciting, but often make you sweat a lot. So that you are armed with answers, today we are going to explain what the conspicuous plastic arrows on the wheel nuts of trucks are all about.

Have you never wondered why some trucks have these plastic accessories in the shape of pointers on the wheel nuts? But you should. Because even if you don't care, if the traffic backs up on your vacation trip, then one of the rear occupants is sure to pester you again about the formidable 40-ton truck in the lane next to you. So that you can then parry confidently in the first row of seats, let's just clarify this now.

If you know the exact name of the distinctive arrow gimmicks, some light comes into the darkness: These are so-called wheel nut indicators. They help to secure truck wheels. What that means? Well, it's very simple: the plastic parts are there to prevent you from being suddenly overtaken by a fat 22.5-inch truck rim, which becomes a highly flammable street missile without an associated vehicle. Ultimately, they serve to prevent accidents caused by loosening the wheel nuts.,

Safety through quick visual inspection

Of course, according to the trade association and its accident regulations, every truck driver has to check the safe condition of the wheels and tires before starting their journey make sure. But let's be honest: Under time pressure and the like, no trucker can constantly check all wheel nuts for tightness. This is where the wheel nut indicators come into play. Because they enable control at first glance - and without torturous activities such as tightening the torque on the truck wheel as a precaution when in doubt.

Pointer direction provides an indication

And the assembly of the indicators? This is very simple and uncomplicated. Because the plastic parts are simply placed on the tightened wheel nuts - so that the directions of the arrows are aligned with each other when there are two nuts lying next to each other. If they are no longer pointing directly at each other, it is immediately clear: Attention, a bolt has loosened here or is at least moving. In this way, you can identify loosening wheel nuts early on, before they become a hazard.

With or without a dust cap, small or large arrow, different wrench sizes - wheel nut indicators are now available in a number of shapes. The original idea came from 1990 and from Mike Marczynski, who was responsible for a commercial vehicle fleet at the time. He first marketed the security product in the UK under the Checkpoint brand name.

Heat warning included

Today, Checkpoint is a successful company with production facilities on four continents and sales in over 90 countries.The wheel nut indicators are now designed for commercial vehicles of all kinds - from the Sprinter class to construction site vehicles and heavy-duty trailers. In addition, the indicators also draw attention to alleged overheating on the wheels - be it due to overheating bearings or brakes. Consisting of specific polymers, they first deform and, in the case of the standard variants, begin to melt at a temperature of 125 °C. There are also models with a higher melting point (165 °C).

By the way: wheel nut indicators can not only be used on vehicles. They can also be used in the industrial sector. Namely wherever the bolts on machines and the like are exposed to high loads, wear and tear or vibration and are constantly in use. This is why the practical safety feature is also used on cranes, conveyor belts or pipelines in the sea, for example.


On trucks, if there are small plastic caps or rings with arrows oriented on the bolt heads of the wheels, these are wheel nut indicators. Even with a brief visual inspection, they reveal immediately whether a bolt on the truck wheel has come loose. They also give an indication of excessive heat build-up because they then begin to melt and deform.


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