Improper trailer hitch extension – A disaster in the making

By Russ and Tiña De Maris
A sharp-eyed Mike Gardner, an RVtravel.com reader, sent us this photo he’d taken. If you look closely and count, you’ll find that some enterprising(?) motorhome user had hitched together four trailer hitch extensions, and used them to pull his toad car. Used properly, a trailer hitch extension is a safe problem solver. Used incorrectly, as in this case, it’s a disaster in the making.

A series of extensions

We don’t know the thinking on the matter, but it appears the RVer wanted to carry a bike rack on his motorhome. A hitch-mounted rack fit his needs. Of course, if the bikes are between the back of the rig and the front of the toad car, you could have a problem when making a tight corner. Maybe he’d found that out the hard way. In any event, he’s strung together a series of trailer hitch extensions, with the bike rack close to the start of the chain.

In the plus column, the user used a hitch tightener/anti-rattle device on each of the connections. That will go a long way to prevent wobbling, rocking, rattling and hitch movement. But, sadly, the negative column far outweighs the good intentions. To find out why, we contacted David Robinson at Roadmaster, a Washington state-based RV tow bar and towing equipment manufacturer. The company has 50 years’ worth of experience under its belt. David is the company’s vice president, and his pedigree includes a college degree in physics.

Laws of physics

Robinson scrutinized the photo and gave us a quick brushup on some of the laws of physics and how they apply to the real world of RV towing. Trailer hitch extensions, Robinson tells us, are great, provided some practicalities are observed. First, when using a trailer hitch extension with a tow bar, you need to remember tow bars are designed for towing – not lifting – a towed vehicle.

Any time you attach an extension between a motorhome (or other tow rig) and the tow, you effectively amplify the effects of leverage. With big Class A rigs, where the rear wheels are close to the end of the unit, leverage isn’t usually too much of a problem. But with Class C units, and even some Class A units where the wheels are farther forward, leverage can become a big deal. Here’s why: On the flat, with everything cruising along happily, the tow bar is doing its job, pulling the toad car, and keeping it steady – all having to do with lateral movement.

But as your tow combination hits a grade, either uphill or downhill, weight is redistributed. Head uphill, and the rear of the coach or tow vehicle will naturally fall closer to the roadway. Head downhill, the opposite occurs, and the rear of the tow vehicle rises farther above the level of the pavement. What happens at the end of the tow ball, where it attaches to the tow bar? It correspondingly rises or falls. David Robinson says in some instances, a coach’s rear end may rise or fall as much as 16 inches.

Slam that pavement!

On a normal roadway, this generally isn’t a problem. But try bringing your tow combination off the street and into, say, a fueling station parking lot. Here’s where that 16” of rise or fall can make a big difference. As the rear end of the coach falls into those sometimes nasty troughs, the hitch-ball end of the system may suddenly slam down onto the pavement. Real damage can result. But the longer the distance between the coach’s rear wheels out to the point of connection with the tow bar, the worse this becomes.

Add more than one trailer hitch extension, the problem becomes multiplied. Robinson told us that over the years, Roadmaster has had plenty of unhappy campers who’ve reported that they’ve done serious damage to their tow bar systems. This has occurred when attempting to enter or exit a steep driveway. As we’ve said, tow bars aren’t designed to deal well with intense lifting forces. There have been instances where motorhome users have actually been rear-ended by their own toad cars. Using an onboard braking system in the toad can alleviate some of the danger.

Wide swings and “de-rating”

Adding more trailer hitch extensions can lead to other problems, as well. As an example, when you roll your motorhome up to the stop line with the intent of making a left turn, what happens? As your coach’s front end moves to the left, your rear end actually moves to the right to make the turn. Stick more hitch extensions behind you and your toad car makes an even wider swing to the right. This sets you up for problems in narrow areas.

But there’s another issue at hand. Every trailer hitch extension manufacturer has a factor, wherein users must “de-rate” their towing capacity by the use of a hitch extension. Across the industry it ranges from 25 to 40 percent. If you unwisely use more than one hitch extension, the factor multiplies. For Roadmaster, this four-fold hitch extension lash-up would actually de-rate the towing capacity of one of their tow bars to something like 800 pounds. There are not too many toad cars that scale in at that flyweight.

Bottom line: Roadmaster’s David Robinson’s advice is this: If you use a trailer hitch extension, make sure it’s rated properly for the load to be towed. Be sure to include the “de-rating” factor. And NEVER use more than one hitch extension. And sure, somebody out there will give us the old, “I’ve been doing this for 20 years and never had a problem.” Fine. But it only takes once.

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