How Does a Trailer Hitch Coupler Work?

by K.K. Lowell

Overview

What a Coupler Is

A trailer coupler is a mechanical device that connects a trailer to the hitch of the tow vehicle. Trailer couplers come in several different configurations, but all work by clamping around the hitch ball. The means to do this varies somewhat. Some couplers employing a hand wheel to tighten the clamp to the ball; another common arrangement is a lever or toggle to lock the coupler.

The Mechanics

When the lever is flipped to the locked position, the clamp is pulled up against the underside of the hitch ball. Proper adjustment is critical to the safe operation of a trailer, so an adjusting nut is provided on the toggle bolt.The fit should be snug but not binding. Too loose, and there's a danger of the coupler becoming disconnected from the hitch ball.

Selecting the Right Coupler

Trailer hitch couplers are rated by weight class: Class I for trailers to 2,000 pounds gross trailer weight; Class 2 for trailers to 3,500 pounds GTW; Class III covers trailers to 5,000 pounds GTW; and Class IV are trailers to 10,000 pounds GTW. Hitch couplers are also available with capacities up to 15,000 pounds GTW. Trailer hitch coupler classes also designate the size of the hitch ball, with the smallest being 1 7/8 inches, the largest being 2 1/2 inches. It's important to match the trailer coupler and ball to the proper loaded weight of the trailer. Doing so will help ensure the highest degree of safety.

About the Author

K.K. Lowell is a freelance writer who has been writing professionally since June 2008, with articles appearing on various websites. A mechanic and truck driver for more than 40 years, Lowell is able to write knowledgeably on many automotive and mechanical subjects. He is currently pursuing a degree in English.