Tongue weight is critical to know, yet simple to calculate and easy to adjust.

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Introduction to How Tongue Weight Works

­Eve­r­yone should know his or her tongue weight. Don't laugh to­o hard about the way that sou­nds­ -- tongue weight is a towing­ term, not something t­o do with the human mouth or dentistry. Tongue weight (TW) is just one of the many towing terms you'll need to familiarize yourself with if you ever intend to tow a trailer behind your vehicle. It's the downward force that the tongue of the­ trailer applies to the hitch of the tow vehicle. Most experts agree that an acceptable tongue weight for any trailer is somewhere between 9 and 15 percent of the gross trailer weight (GTW). There's good reasoning behind these numbers, too. It all comes down to trailer towing safety.

If the tongue of the trailer does not exert enough downward force on the tow vehicle's hitch ball -- meaning that the trailer's tongue weight is too light -- a dangerous condition called trailer sway could result. If the tongue weight is too heavy, the steering of the tow vehicle will be affected. This makes it sound like tongue weight is a big deal, and it is. But fortunately, tongue weight is also easy to adjust.

Just remember that the trailer acts like a lever, and the axle of the trailer is the fulcrum -- or pivot point -- for the lever. If the tongue is too light, you need to move some of the cargo forward of trailer's axle. If the tongue is too heavy, you need to adjust the load so that more of the weight is behind the trailer's axle. It's just like trying to balance the weight of two kids on a seesaw at the playground. That's easy enough to understand, but other than simply lifting the tongue of the trailer and guessing its weight, how could you ever know how much the trailer's tongue truly weighs? And an even better question may be this: How would you determine if the tongue weight falls within the 9- to 15-percent range of the gross trailer weight? Read the next page to find out how you can do just that.

The front wheels of the tow vehicle are barely on the ground. Is the tongue weight too heavy?

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Calculating Tongue Weight

Finding the tongue weight (TW) of any trailer can, at first, seem like a difficult task. Fine-tuning the tongue weight to fall within the 9- to 15-percent weight range of the gross trailer weight (GTW) might seem nearly impossible. You'll be happy to know that it doesn't have to be complicated at all.

Most trailer owners already know their gross trailer weight -- the actual weight of the trailer. If you don't know your gross trailer weight, then you'll need to plan a trip to the local public scales. With an investment of only a few dollars and just a little bit of your time, you can get some valuable information. Knowing your gross trailer weight is critical to properly adjusting the tongue weight of your trailer. In fact, it's your starting point in a very simple equation.

As an example, let's say that your gross trailer weight is 564 pounds (256 kilograms). If you're trying to adjust your tongue weight to 11 percent of the gross trailer weight, then you want the tongue to weigh 62 (28 kilograms) pounds. Easy enough -- but how do you find out how much the tongue weighs right now?

Since this is a smaller trailer, you can measure the weight of the tongue using a standard bathroom scale. The trick is to make sure that the scale is at the same height as the hitch ball on the tow vehicle. Usually a small box or a cinder block will do the trick. Next, carefully place the tongue of the trailer directly on the scale and read the weight. This is your tongue weight. If the tongue weight is more than 62 pounds (28 kilograms), then you need to move some of the trailer's cargo rearward so that more weight is carried behind the trailer's axle. If the tongue weight is less than 62 pounds (28 kilograms), then you'll need to adjust some of the cargo toward the front of the trailer so more weight is carried in front of the trailer's axle. Keep your eye on the scale and you should be able to hit the target tongue weight.

For much heavier trailers -- those with a tongue weight that would exceed the weight limit of a standard bathroom scale -- you need to employ a slightly different technique. There are two very good options available to you. First, you could purchase a tongue weight scale that's designed specifically to measure trailer tongue weights (up to one ton). Or, with a little extra effort and some additional setup time on your part, you can use the same standard bathroom scale.

To do this, you'll need a two-by-four cut to a five- or six-foot (1.5- or 1.8-meter) length, two pipes, your bathroom scale, and a brick. Lay one of the pipes across the scale and the other across the brick. Position the scale and the brick so the pipes are exactly three feet apart. Now, lay the two-by-four across the pipes, and find a suitable way to support the tongue of the trailer at the same height as the tow vehicle's hitch ball. Place the tongue (and hitch-height support) on the two-by-four exactly 2 feet (0.6 meters) away from the pipe lying across the scale and 1 foot (0.3 meters) away from the pipe lying across the brick. Read the weight displayed on the scale, and then multiply the weight by three. This is your tongue weight. As with the method we used for the smaller trailer, you can adjust the weight of the cargo forward or rearward of the trailer axle to reach your target tongue weight. Just watch the scale -- and don't forget to multiply the displayed weight by three.

Calculating tongue weight isn't really that complex. In fact, with enough practice, you'll soon be a pro at finding tongue weight -- and the way your trailer handles on the road will reflect that.

If you're interested in reading more about vehicle weight, towing and other related topics, follow the links on the next page.

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  • "Automotive Glossary: Tongue Weight." (Sept. 26, 2008)
  • Curt Manufacturing. "Understanding Towing: Tongue Weight." (Sept. 26, 2008)
  • "Tongue Weight (TW)." (Sept. 26, 2008)
  • U-Haul. "Towing glossary: Tongue weight." (Sept. 26, 2008)