fifth wheel

(redirected from fifth wheels)
Also found in: Dictionary, Thesaurus.

fifth wheel

[¦fifth ¦wēl]
(mechanical engineering)
A coupling device in the form of two horizontal disks that rotate on each other positioned between a tractor and a semitrailer so that they can change direction independently.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
"The fifth wheel with offroad-capability compensates for pitch and roll movements, which is a special advantage for transports on difficult terrain.
When a trailer kingpin is properly coupled to an ELI-te equipped fifth wheel, four high-intensity white LED lights mounted within the component automatically illuminate the lockjaws.
Approved for all on-highway standard-duty applications, the FWAL is the world's lightest weight and only aluminum standard-duty fifth wheel. Combining proven SAF-Holland fifth wheel engineering and advanced ALCOA aluminum forging technology, the FWAL is up to 100 lb.