How Hitch Safety Chains Work

In May 2007, a small trailer became unhitched from the Lincoln Navigator towing it on Maryland's Chesapeake Bay Bridge. The trailer flew backwards, causing a seven-vehicle crash that killed three people. The Navigator had hitch safety chains, but investigators said they weren't installed properly and that the trailer didn't have a safety pin [source: McCaffrey].

This is an example of the kind of damage a trailer can do when it's not properly secured with hitch safety chains. If the trailer coupling separates from the ball mount, or the ball disconnects from the hitch, the chains will keep the trailer from drifting down the road during towing. They are designed to keep your vehicle and trailer attached long enough for you to safely come to a stop and properly reattach them. They're usually metal links between 18 inches and three feet in length. Some drivers opt to use vinyl-coated safety cables to minimize noise.

Whether you're towing short distances or going cross-country, it's important to always use safety chains. At the same time, remember that safety chains aren't meant to tie something down or to tow another vehicle out of the mud, like hitch hooks and anchors. Hitch safety chains are used more as an insurance policy against

In this next section, we'll discuss how to properly install this piece of towing equipment on your vehicle.

Installing hitch safety chains takes a few extra minutes when you're preparing for a road trip with your trailer, but they'll be well worth it to keep your towing equipment safe. Whether you decide to use cables or chains, make sure they can support whatever you're towing. On many Web sites that sell towing accessories, you will see listings for "Class II" or "Class IV" chains. This refers to the weight of your trailer [source: Trailer Hitches]. In short, don't get hitch safety chains too weak to hold whatever you're towing. The sizes of the chains you get also depend on your towing vehicle. Most light duty trucks will use 5/16-inch thick chains. Most medium-duty trucks use half-inch chains, and heavy-duty vehicles handle 5/8-inch chains [source: AW Direct].

Here's how to install them:

Have two chains crisscrossing under the trailer tongue connecting the trailer to the bumper or the receiver on your towing vehicle. Attachment devices (like trailer hooks) at the end of the chains should be sturdy and solidly in place [source: Lamm]. If the chains are too long, they can be twisted until they're short enough. Also, wires should be used at the hook points to keep the chains from accidentally falling off. Make sure you then attach the chains to the towing vehicle itself and not to another part of the trailer hitch. This ensures that the two units will be kept together if the coupler separates from your receiver unit. Crossing the chains under the tongue will allow them to form a net that catches the trailer's tongue in case it breaks loose and falls to the roadway.

The chains must be small enough to keep the trailer from drifting but with enough slack to allow the towing vehicle to turn with ease. They also shouldn't be allowed to drag on the ground.

For more information on hitch safety chains and proper towing techniques, please see the links on the following page.