Loose wheel nut indicator

Loose wheel nut indicators are small pointed tags, usually made of fluorescent orange or yellow plastic, which are fixed to the lug nuts of the wheels of large vehicles.[1] The tag rotates with the nut, and if the nut becomes loose, the point of the tag shifts noticeably out of alignment with the other tags. If too many lug nuts are loosened, the wheel can detach from the wheel stud; loose wheel nut indicators allow identification of loose nuts before this can occur.

A single wheel nut indicator.
Wheel nut indicators on a truck showing all nuts are as they were left.

Loose wheel nut indicators or lug nut indicators are used both by auto mechanics and drivers to identify lug nuts which require tightening, as well as by accident investigators to detect faults after accidents. Although generally not compulsory, road safety bodies frequently recommend their use,[2][3][4] especially on large or heavy vehicles such as buses, coaches, large vans, and trucks.[5]

An alternative to wheel nut indicators is to add a torque stripe. This is a small strip of polymer connecting the nut to the surface it is fastened to which breaks if the nut loosens.

References
  1. "What are the yellow plastic indicators on truck and bus wheels".
  2. "Highways Agency UK, Vehicle Wheel Nut Indicators" (PDF).
  3. "Transport for New South Wales, Safety Technologies for Heavy Vehicles and Combinations, P.11" (PDF).
  4. "NZ Transport Agency, Wheel Loss Information Sheet, P.2" (PDF).
  5. "Wheel Loss". Brake. Archived from the original on August 10, 2007. Retrieved 2007-08-19.
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