Understanding Trailer Weight Safety
You may be wondering what all this talk is about gross vehicle trailer weight, tongue weight, etc. I've put together an explanation of all the weights you need to know about in order to properly select your hitch equipment. A trailer chassis (springs, wheels, tires, axles, frame and tongue) is designed to carry a certain maximum load.
This load consists of the empty trailer itself, plus weight added in the form of water, food, clothing and anything else that may be stored in or attached to the trailer. The maximum load for which the trailer is designed is called the GROSS VEHICLE WEIGHT RATING (GVWR). This is the total of the weight on the axles and weight on the trailer tongue or fifth wheel kingpin.
The maximum trailer weight a specific axle is designed to carry is the GROSS AXLE WEIGHT RATING (GAWR). Again, the rating represents the empty vehicle’s axle weight plus the maximum added load. On trailers with more than one axle, the weight is divided between each axle and each has its own GAWR. The total of all axle loads plus the tongue weight must not exceed the GVWR. All of these ratings are found on the Federal Certification Sticker on the tongue of your trailer. This label is attached on the front roadside of the trailer. Ask you dealer or hitch installer where it is located if you are not sure.
To be safe, you must compare the actual trailer weight (loaded) of your trailer with the GVWR rating on the sticker.
How, you may ask, do I do that?
Well, there are two ways to accomplish this. You can take your rig to public government scales located off the highways (Weigh Stations) and weigh your vehicle. Or you can weigh your rig at small private scales operated at grain elevators, scrap material yards, sand plants, rock quarrys and other types of businesses.
Look in the Yellow Pages under Scales, or Scales-Public Weighers. These private scales will usually charge a small fee for issuing a certificate of weight. Some will not charge if you don’t need a certificate. The advantage of the private scales is that if you are overweight, you won’t get a ticket like you will at a Public government scale. Always ask permission and try not to go during busy hours.
If the loaded weight of your trailer exceeds the GVWR, you’ll have to remove items to bring the weight down to or below the GVWR. Here’s how you can figure out your weight at the scales:
- Weigh the trailer by itself. After driving the vehicle and trailer onto the scale, disconnect the trailer from the tow vehicle and move the tow vehicle off the scale. This figure must not exceed the GVWR of your trailer.
- Find the tongue weight. Tongue weight is the amount of downward pressure exerted by the trailer tongue onto the hitch ball. Move the trailer until the tongue is off the scales. Re-level the trailer by adjusting the height of the tongue jack. Read the trailer weight on the axles alone. Subtract weight on the axle from the total weight. This weight difference will be the approximate tongue weight.
- For small trailers, you can place the tongue on a bathroom scale. This won’t work for trailers with tongue weight over 300 lbs. For heavier trailers, use the method shown below. Be sure the trailer is level. Measure from the ground to the bottom of the frame at the rear of the trailer and also at the front of the trailer. The amounts should be equal when it’s level. Don’t use a level stick!
Once you have calculated the tongue weight on your trailer, you need to make sure the figure does not exceed the recommended load for your trailer. If the tongue weight is below the recommended amount you must move some of the load forward or strap a heavy object like a toolbox to the front frame of the trailer. If the tongue weight exceeds the recommended amount you must shift some of the load rearward in the trailer. Here are the recommended weight distribution figures:
|Tandem Axle Trailer||9%-15%|
|Single Axle Trailer||10%-15%|
|Fifth Wheel Trailer||18%-20%|
Here is the formula for calculating tongue weight:
Be sure you are loaded the way you anticipate traveling. If you expect to carry water or gasoline (in a boat), be sure your tanks are full, before doing your weight calculations.
4. Drive onto the scale loaded with all supplies, passengers, and equipment. Take a weight reading. Check the weight capacity of your tow vehicle in the owner’s manual. You must not exceed the capacity of the tow vehicle.
Proper Weight Distribution is required for towing stability and will assure that the trailer is not rear, front or side heavy. A light tongue weight or heavy weights placed at the rear end of the trailer can cause sway. On the other hand, too much weight on the tongue can overload the tow vehicle and cause poor tow vehicle braking, poor cornering and can damage the trailer frame.
Why am I spending so much time on weight? Well, as you will see, weight is the most important factor in determining towing safety and is where most mistakes are made. While it is very important that you know the total weight you are towing, and the total weight capacity of your tow vehicle and hitch, it is also just as important to know how to load your vehicle for safety.
A properly loaded trailer will perform better and handle more safely. You should always store heavier items on or close to the floor and as centrally as possible. Lighter items may be stored in upper cabinets, closets and drawers. Luggage or similar cargo transported inside your RV should be secured to prevent it from causing damage in case of a sudden stop.
When loading a trailer, store heavy gear first, keeping it as close to the floor as possible. Heavy items should be stored directly over or slightly ahead of the axles. Store only light items on high shelves. Distribute weight to obtain even side-to-side balance of the loaded vehicle.
For truck campers, first and foremost, you must not install a heavy camper on a light duty truck. The combination may result in damage, poor performance, hazardous handling and possible injury. When loading the camper, store heavy gear first, keeping it on or as close to the floor as possible. Place heavy things far enough forward to keep the loaded camper’s center of gravity within the zone recommended by the truck manufacturer. Store only light objects on high shelves. Distribute weight to obtain even side-to-side balance of the loaded vehicle.
To illustrate an actual example of how to use your new knowledge of weight ratings, here is a sample (partial) description that appears with an actual trailer in it’s brochure:
|Unloaded trailer weight (with hitch weight)||7200 lb|
|Gross vehicle weight rating||11,000 lb|
|Net carrying capacity||3900 lb|
|Hitch weight||1200 lb|
|No. of Axles||2|
What we’re looking at here is the manufacturer’s specs on a 33-foot long travel trailer, which in this case has a 13-foot slide-out room in it. The GVWR is 11,000 lb. That is the most weight the chassis of this trailer can handle. The unloaded or dry weight is 7200 lbs. So, if you subtract the unloaded trailer weight from the gross vehicle weight rating, you get the net carrying capacity.
This is important because it tells you how much “stuff” you can load into this trailer and still remain within the guidelines for towing safely. This “stuff” includes water, clothes, food, bikes, gear and any options you may have added onto the trailer like air conditioning, generator, storage pod or TV dish etc. (Storage pods on top of an RV must not exceed 100 lbs including the cargo and pod weight).
Hitch weight is another name for tongue weight. Be aware of these weights to make sure your tow vehicle can handle this trailer. The owner’s manual that comes with your truck, SUV or van will tell you how much weight you can handle. Don’t even attempt to tow more than your vehicle can handle!
A friend of mine learned this weight lesson the hard way when he was taking a trip to Nevada. He had unthinkingly loaded several cases of soda in the very back of his trailer. In addition, all the holding tanks, (located in the rear of the trailer) were full and the water tanks, (located in the middle of the trailer) were empty, as he was heading home. He also had a couple of extra full propane tanks stored in the back of the trailer. As he was chugging along the highway, he slightly jerked the wheel and the trailer suddenly started to sway dangerously.
To get out of the situation he kept his foot on the accelerator and manually held the trailer brake control on until he was able to stop the rig in a straight line. (By the way, most people would have slammed on the brakes, which is the absolute WORST thing you could have done in this particular situation). Of course, he immediately moved the heavy items in the back of the trailer up to his pickup bed to redistribute the weight and relieve the danger. It’s safest to empty your gray water and waste tanks before traveling.
So, believe me, understanding your weight capacity and sticking to it, and distributing your cargo evenly can help you avoid an accident and even save your life and the lives of others. That’s why I’ve spent so much time on this aspect of towing safety.
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