Towing Basics.

 


From weighing and weight ratings to hitches and tire pressure, learning the details now can save you a lot of trouble on your next vacation
BY: Chris Hemer

Of all the things RVers do with their vehicles, towing has to be the most misunderstood activity of all. It seems simple enough; equip your truck or SUV for towing, hitch up and go, right? Not so fast. Just because your tow vehicle can tow the trailer you've matched it with doesn't necessarily mean that it isn't overloaded or improperly loaded, or that your rig will handle predictably and safely when you're on the road.

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Whether you've never towed before, only tow occasionally, or purchased your vehicle specifically for the purpose of towing, it pays to know the basics before you head out on your first journey. From vehicle weight ratings, weighing and weight distribution to hitches, trailer brakes and tire ratings, there is an awful lot to understand in order to ensure a safe towing experience.

LOADING

Quite simply, everything you do with regard to prepping your truck for towing is directly related to the amount of load you intend to pull. For simplicity's sake, we'll assume that you have a truck as a tow vehicle, although the same rules apply for an SUV, van, even a car if it is rated for towing and is properly equipped (although the equipment may vary significantly).

The first thing you should seek out is the truck's max trailer rating, or towing capacity. The max trailer rating is the maximum amount of trailer weight your truck is rated to pull. All things being equal (example, comparing one half–ton truck to another), your truck's max trailer weight rating is based on a number of criteria, such as its weight, engine, gear ratio, brake size, tires, and the like. Your owner's manual may contain information on your truck's rating, and if not, most manufacturers publish "towing guides" that establish the maximum tow rating of your vehicle, based on its equipment (Trailer Life magazine also publishes an annual towing guide).

Because your vehicle's tow rating is based on so many different criteria, it is important to note that you cannot upgrade your vehicle's tow rating. A lot of people have written in to us, saying they are going to be buying a new trailer, and want to know what products they should add to increase the vehicle's tow rating. While changing gears to a lower ratio, adding a high–performance air intake and headers/exhaust/programmer will all aid in the towing performance of a properly–loaded truck, they will not increase its towing capacity. If the trailer you plan to tow weighs more than your truck's rating, either choose a lighter trailer or a buy a heavier duty truck.

It is quite common to find people who routinely overload their trucks, and think nothing of it. They believe that tow ratings are just a guide, and that overloading won't hurt. Truth be told, overloading your truck once in while for a short distance probably won't cause any damage–but there are other, equally important issues to consider, such as stopping distances and safe handling. Overloading severely degrades your truck's ability to stop quickly or to handle predictably in an emergency situation–and could cause a serious accident.

In the long run, overloading will create pre–mature wear on tires, brakes, transmission, bearings and other components, which at the very least will inflate your vehicle maintenance bills. In a worst–case scenario, outright component failure and a possible accident can result.

That said, it is important to know not only your truck's towing capacity, but how much the trailer you plan on towing actually weighs–and by that we mean how much it will weigh when you tow it. For example, if your truck is rated to tow 8,000 lbs., don't purchase a trailer that weighs 8,000 lbs. or even 7,500 lbs. and expect it to be within your truck's towing capacity. Once you add water, (8.3 lbs. per gallon) propane (4.5 lbs. per gallon), batteries (50 lbs. or more each) supplies and toys, it will almost certainly be too heavy for your truck to pull safely.

To determine the weight of the trailer in question, first see if it is equipped with a weight label. Trailers built from '96 and up are equipped with a Recreational Vehicle Industry Association (RVIA)–mandated label that states the Unloaded Vehicle Weight (UVW) for the trailer. This is the weight of the trailer including factory–installed options, but no freshwater, propane or dealer–installed options/accessories. If the trailer in question was built prior to 1996, you should still be able to obtain a "dry weight" figure somewhere in the trailer, which will provide you with a similar figure. With this information in hand, make a rough calculation of how much weight you plan to carry, and determine if the total weight exceeds your truck's rating or not. In any case, it's a good idea to stay within 10% of the vehicle's maximum tow rating to ensure adequate performance. So, if the truck has an 8,000 lb. towing capacity, the ideal maximum trailer weight would be 7,200 lbs., with water, propane, batteries and all supplies on board.

If you can take the trailer and your truck to a scale, this is, of course, the best way to determine actual trailer weight. Even if you can't load it with all of your supplies, you can weigh it, then factor in the weight of water (based on the freshwater capacity), propane (based on the size of the propane cylinders) and batteries, then give your best estimate of the stuff you'll bring along. Weighing the trailer will also help you determine if the trailer's Gross Axle Weight Rating (GAWR) or tire load ratings have been exceeded and can help you measure hitch weight as well.

If you can't weigh the trailer, use the trailer's Gross Vehicle Weight Rating (GVWR) as your guide; if it is within the maximum tow rating of your truck, you will be able to tow it, provided you don't overload the trailer, of course.

If you've got an older truck for which no towing guide is available, the best advice we can give is to determine the GAWR for the rear axles, and don't overload them; equip the truck with the proper load–rated tires for the job at hand, and weigh the truck/trailer combo to be sure that neither the Gross Combination Weight Rating (GCWR) nor the GVWR have been exceeded. Towing performance will, of course, vary depending on how your truck is equipped. And with older trucks, you may have to let common sense be your guide; if the truck seems like it's really working hard to tow the load, it probably is–and it's probably overloaded.

HITCHING UP

Once you have determined that your truck is capable of pulling the trailer, you need to determine which class of hitch your truck is equipped with, or what it will need to be equipped with on order to tow the trailer you are considering.

With travel trailers, there are two types of hitches: Weight carrying, and weight distributing, both of which slide into a hitch receiver on your truck. Weight carrying hitches are so named because they carry all the hitch weight of the trailer; you simply drop the trailer on, lock it down and go. These are most commonly used with lightweight trailers with little hitch weight, such as an ATV or tent trailer, for example.

A weight distributing hitch is a heavier–duty piece that uses distribution bars to distribute the weight more evenly, that is to say, it takes some of the weight off the rear of the tow vehicle and shifts it forward, and takes some of the weight from the front of the trailer and shifts it rearward. These hitches increase stability dramatically when towing a heavier travel trailer (especially when used with a sway control device) and reduce the strain on your tow vehicle tremendously.

Clearly, which hitch you use depends on the weight you plan to pull, and/or the type of hitch receiver your truck is equipped with. For example, Reese lists the various hitch classes and their rated capacities for a weight carrying hitch application as follows: Class I, 2000 lbs; Class II, 3,500 lbs.; Class III, 5,000 lbs.; Class IV, 12,000 lbs.; Class V, 13,000 lbs. Note that the maximum tongue weight these hitches are designed to accommodate is typically 10% of the trailer's gross weight.

Trailers light enough to be handled by a Class I or Class II hitch receiver typically don't require a weight distributing hitch, but when you move up to a trailer heavier enough to require a Class III or better hitch, then a weight distributing design should be used. With a weight distributing hitch in place, note the increase in the gross trailer weight limits: Class III, 10,000 lbs.; Class IV, 15,000 lbs.; Class V, 17,000 lbs. Because a weight distributing hitch effectively spreads the load out over the truck and trailer as described above, the receiver no longer has to bear all of the hitch weight, and can therefore handle a larger, heavier trailer.

When using a weight–distributing hitch, the goal is to have the trailer level, and the tow vehicle in the same attitude as it was before hitching. To achieve this, measure the tow vehicle at reference points on the front and rear bumpers, then hitch up the trailer and adjust (increase) the spring bar tension until the measurements are approximately the same with the trailer hitched up. If the spring bars cannot be adjusted tight enough to achieve the desired attitude, stiffer spring bars may be required. On the other hand, if the tow vehicle is at the desired attitude but the trailer is not level, the ball mount should be raised or lowered as necessary. As its designation would suggest, adjustable ball mounts allow the ball height to be adjusted, and once you've got your hitch set–up dialed in, you won't need to adjust it again for the same trailer. Obviously, more explanation than we have room for here is required to adequately describe proper hitch adjustment, but a qualified RV center will be able to provide you with the finite details.

For really heavy loads, you'll need a fifth wheel (recreational use) or a gooseneck (commercial use) hitch. These hitch systems both mount in the bed of the truck, but differ in that a fifth wheel has the hitch saddle or coupler in the bed and a hitch pin on the trailer, while a gooseneck uses a hitch ball in the bed of the truck, and the coupler is on the front of the trailer. These hitches provide the greatest amount of stability because the pivot point of the truck and trailer is moved forward, so the trailer cannot "wag" the tow vehicle the way a travel trailer can. It used to be that if you had a fifth wheel hitch you could not tow a gooseneck trailer and vice–versa, but now, hitch manufacturers such as BW have come out with systems that can convert from gooseneck to fifth wheel hitch set–up and back again in just a few minutes. In any case, the trailer's hitching point should be located at the center line of the truck's rear axle or slightly forward to achieve maximum stability, but any qualified RV center should know this and install the hitch system accordingly.

Understanding weight limits and using the correct hitch and hitch equipment are the keys to a safe and enjoyable towing experience. Use your truck and trailer wisely, and they will provide many memorable trips to come.