- The Washington Times - Friday, April 5, 2002

Judging by the amount of reader mail we receive about the subject, making a proper matchup between a tow rig and a trailer is a popular and often confusing subject. Even with a lot of information readily available from different sources, it can still be difficult to sort out what's important and to make a good decision.

The towing guides published by the car and truck manufacturers are gold mines of information for the trailering enthusiast. Ford, General Motors and Dodge seem to have the best handle on what's important for making an informed decision about a new tow vehicle.

RVers approach this problem in three different ways.

One, they plan to buy a tow rig and trailer and are shopping for both vehicles.

Two, they already own a tow rig and want to choose the right trailer to go with it.

Three, they own a trailer and are looking for a replacement tow rig.

It's good to know how all the specification numbers work together during such a shopping venture, but in the third case, it's vitally important to know what the trailer actually weighs before choosing a tow rig. To facilitate this decision, start with the trailer set up more or less as if it's ready to go on a trip. Fill the freshwater and LP-gas tanks, and have the trailer loaded with the average cargo load you take along on an RV outing.

Bring the tow rig and trailer to a public weigh scale. These can be found at moving and storage companies, gravel pits, public truck stops, feed mills or grain elevators, recycling centers and the like. Many such places are pretty busy so you won't be able to take the time to unhitch the trailer on the scale, so you'll need to do some calculations to find out the trailer weight.

First, weigh just the tow rig with the trailer axles off the scale; then weigh the entire combination. Now pull off the scale and find someplace close by where you can drop the trailer. Then go back and weigh just the tow rig alone. Figure the trailer weight by deducting the tow rig weight from the total combination weight. Trailer hitch weight is the tow rig with trailer hitched, minus tow rig alone.

As an example, say the tow rig with trailer hitched is 8,000 pounds; the total combo is 15,000 pounds and the truck alone is 6,000 pounds. The trailer weight is 15,000 pounds minus 6,000 pounds, or 9,000 pounds. The trailer hitch weight is 8,000 pounds minus 6,000 pounds, or 2,000 pounds. That's how you determine your trailer weight, which is part of the matchup process. The aforementioned towing guides help you learn how much each vehicle is rated to tow.

You should always make a tow rig/trailer matchup such that you allow some extra weight capacity above the trailer weight and below the tow rig's tow rating.

In the above example, you wouldn't want to select a truck that's rated to tow exactly 15,000 pounds, even if that's the trailer's ready-to-go weight. You're still going to add passengers and some cargo to the tow rig, and you may also add more weight to the trailer.

Say, for example, you have a sport utility vehicle that's rated to tow 7,000 pounds. If you choose a trailer that weighs close to 7,000 pounds, according to the manufacturer's guess, you'll probably overload the SUV by exceeding the manufacturer's tow rating. Despite strict standards for weight labeling now in effect, you still need to allow for the weight of cargo, fluids and manufacturer or dealer-installed options on the trailer.

Let's start with a 5,500-pound trailer for the above SUV. With 40 gallons of water, or 40 x 8.2 pounds = 328 pounds, and 20 pounds of LP-gas aboard, the trailer weighs 5,848 pounds. If it has options not listed on the weight label such as an air conditioner, awning, and the like that adds more weight. Add personal cargo, food, sporting goods, tools and the like, and the trailer may be well above 6,300 pounds or so. Carry four passengers in the SUV, at a Department of Transportation average of 154 pounds each or 616 pounds total, plus some cargo in the SUV, and it's not hard to see how that 5,500-pound trailer is pushing against the SUV's 7,000-pound tow rating.

If you'd started the process with a trailer closer to the tow rating, it's easy to overload the SUV's tow rating. The same is true when shopping for a tow rig and you already have a trailer. Allow some leeway in the tow rating, or the trailer weight, to have weight capacity to spare for cargo, passengers and the rest of the necessities you haul along.

Do a few calculations before you buy, and you can make a safe tow rig and trailer matchup the first time out.