RV Shopping: Weight Distribution and Sway Control

Lisa Fritscher May 18, 2012 No Comments

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Flagstaff 27RLSS Travel Trailer

Our new Flagstaff 27RLSS is long and heavy

When purchasing a new travel trailer, it is very important to familiarize yourself with several numbers that, when taken together, demonstrate the ability of your tow vehicle to safely pull your chosen trailer. However, even crunching the numbers is not always enough. When towing a heavy or long travel trailer, you must also consider weight distribution and sway control. These factors are critical to a safe towing experience and the best choice of equipment varies for each combination of tow vehicle and trailer. Below is a general guide based on my own experiences, but it is always best to speak with the manufacturers of both the tow vehicle and the trailer to ensure that you have the best possible setup for your individual needs.

Weight Distribution

Trailer hitches come in two basic forms—weight-carrying and weight-distributing. As the name implies, a weight-carrying hitch sits on the bumper of the tow vehicle and takes the full weight of the trailer tongue. These hitches are common and relatively safe for very lightweight trailers. As the weight of the trailer rises, however, weight-distributing hitches become critical.

Weight distribution and sway control system

This is an example of a combined weight-distribution and sway control system

A weight-distributing hitch attaches to a receiver mounted on the tow vehicle’s frame beneath the rear bumper. Vehicles that are designed for heavy trailer towing have both a hitch receiver and an electrical connection to plug in the trailer. To safely tow a trailer that weighs over 5000 or 6000 pounds (depending on the tow vehicle manufacturer), the tow vehicle needs to be specially equipped. Among other upgrades, a properly equipped tow vehicle is outfitted with a heavy duty hitch receiver and a 7-pin electrical connector. On some vehicles, these items are standard equipment. On others, they are part of an optional package. For some older vehicles, it may be necessary to add each item individually to the vehicle. Always check with your vehicle manufacturer to ensure that you have all necessary equipment to safely tow a heavier trailer. Also check the manufacturer’s towing guide to learn the weight limitations of your tow vehicle.

As an example, Dad and I drive a 2007 Ford Expedition Eddie Bauer with the optional Heavy Duty Towing Package. This package includes an auxiliary oil cooler, an upgraded radiator, heavy duty flashers, a trailer brake wiring kit, a hitch receiver, and a 7-pin wiring harness and connector. According to the Ford Towing Guide, we can tow a 6000 pound trailer with a 600 pound tongue on a weight-carrying hitch, or a 9200 pound trailer with a 920 pound tongue on a weight-distributing hitch. If we had a 2012 Ford F-350 DRW truck, we could tow a 15000 pound trailer with a 1500 pound tongue on a weight-distributing hitch.

What a Weight-Distributing Hitch Does

As the name implies, a weight-distributing hitch distributes the weight of the trailer tongue among the three axles—the front and rear axles of the tow vehicle, and the axle of the trailer. The weight distribution system that you choose should be able to handle more than the tongue weight of the trailer, but not too much more. If you choose a 1500 pound system for a 400 pound tongue, the weight distribution will be too great. You need to have 10 to 15 percent of the total trailer weight on the hitch. Any less and you may experience dangerous and unpredictable sway. Likewise, a system rated for 1000 pounds is virtually useless for a 1500 pound hitch. The distribution will be improper. Theoretically your tongue weight might still end up in the 10 to 15 percent range, but the weight distribution system will not perform as predicted.

Sway Control

sway control and weight distribution bars

Integrated sway control works with the heavy weight distribution bars

Although it is possible to install either portion separately, sway control systems typically go hand in hand with weight-distributing hitches. In an ideal world, a properly loaded and balanced tow vehicle and travel trailer combination will not sway. In reality, however, it only takes a sudden gust of wind, being passed by a semi-truck (the infamous “truck suck”) or even a moment’s inattention to the road for a dangerous sway condition to develop. When my parents first bought the old RV in 2004, the dealer told them that he had plenty of customers turn down sway control, drive a few miles down the highway, then turn around and come back for a sway system.

The problems of sway are exacerbated by not only loading and balance, which are reasonably easy to correct, but by the length and weight of your travel trailer compared to the length and weight of your tow vehicle. In general, a short wheelbase vehicle such as an SUV or a short bed truck is more prone to trailer sway, particularly as the length of the trailer approaches or exceeds 30 feet. A trailer that weighs as much as or more than the tow vehicle is also more likely to sway.

Keep in mind that trailer lengths can be misleading. In older trailers, the model number typically gave the overall exterior length of the trailer. Our 2004 Road Runner XL 27RB was 27 feet long from tip to tail. Today, however, the model number generally refers to the interior length. Our new 2012 Forest River Flagstaff 27RLSS is 27 feet long in the living area, but 31 feet long overall—four feet longer than the old trailer. The exterior length is usually listed on a chart in the manufacturer’s brochure and website, but be sure to ask if it is not readily apparent. We looked at a few RVs that were 30 feet long inside, but more than 36 feet overall!

Sway control is available in three main types—friction, adaptive, and predictive. All three types work well under the conditions for which they were designed. Each RVer has his or her favorite type of sway control system and one or two that are absolutely hated. The problem is that one person’s hated sway control is the next person’s favorite. As a very general rule of thumb, friction systems work extremely well on shorter and lighter trailers, while expensive predictive systems are considered the gold standard for heavy, long trailers towed by vehicles with a short wheelbase. That said, however, many people successfully tow long trailers with friction systems and many prefer an adaptive or predictive system for even a relatively short trailer.

Before choosing your weight-distributing hitch or sway control system, do a great deal of research. Visit the websites of various hitch and sway control manufacturers and learn how that particular system works. Visit Internet forums for RVers, particularly those frequented by full-timers. Ask detailed questions about your particular combination, and take all opinions to heart.

Ultimately, the only way to decide which system is right for you is through real world experience. Though it can be an expensive lesson if your first choice doesn’t work out, it is important to thoroughly test out your new system. Hitch up and drive (carefully) in a variety of road and weather conditions. Stop and start at low speeds, try out city traffic and drive on the highway. If your trailer sways, begin by readjusting the sway control system or pay an expert to adjust it for you. As long as all of your weights are balanced, most minor sway problems can be corrected by playing with the settings on the sway control system. But if you are unable to get sway under control, consider purchasing a different system. Compared to the price of your tow vehicle and your travel trailer, not to mention the fact that the lives of your family and others on the road are on the line, even buying two or three systems is a relatively small investment.

Brake Controllers

Trailer Brake Controller

The brake controller controls the trailer brakes. Pretty important equipment!

As mentioned above, my parents’ RV dealer made a huge deal out of the need for a sway control system. And he was absolutely right. With the sway control system he sold them, we were later able to trade the long wheelbase van in on a short wheelbase Expedition, and successfully towed the 27 foot travel trailer all through the windy American Southwest. We are now looking to upgrade our system, as the new 31 foot trailer is slightly too sway-prone for the old system.

What that dealer never mentioned to my parents, however, is a brake controller! Without a brake controller, the trailer brakes will not activate, forcing the tow vehicle to stop the entire combination. Brake controllers are legally required in all states for trailers over a certain weight, though the exact weight varies from state to state. When we were shopping for our new travel trailer, however, all of the dealers we talked to were in agreement that our old trailer, which weighed in at just over 6000 pounds fully loaded, definitely needed a brake controller. We were fortunate indeed that we were able to successfully tow through the mountains, considering our trailer brakes were never engaged! At nearly 7500 pounds fully loaded, our new travel trailer certainly needs its brakes.

A brake controller activates the trailer brakes when the vehicle brakes are applied. The brake controller itself is a small box mounted within easy reach of the tow vehicle driver. There are two types of brake controller—proportional and time-delayed. Time-delayed controllers always provide maximum braking power at a preset interval after initial vehicle braking. Proportional controllers apply the trailer brakes in tandem with the braking power applied on the vehicle brakes. Both types of system have their fans, and in general, both work well. Base your decision on the recommendation of your dealer in tandem with detailed Internet research.

A Word on Dealers

RV Dealers

RV Dealers don't always know which system is best for you

We spoke to dozens of RV dealers during an intense two months of shopping for our new travel trailer. We found that for the most part, dealers care about helping customers select the RV that is truly right for them. As in any industry, though, we found extremely good dealers who go above and beyond the call of duty, and extremely bad dealers who care only about making a sale. We also found quite a few well-meaning dealers who were not well versed in the particulars of towing with an SUV.

Ultimately, you have the responsibility for the safety of yourself, your family and other drivers with whom you share the road. It is up to you to learn and understand the capabilities and limitations of your tow vehicle. Some dealers will say, “Your vehicle will tow anything on the lot!” Others prefer, “Don’t worry that the hitch weight is over your specifications. A weight-distributing hitch will take care of that.” These and similar statements are not necessarily red flags, but they are yellow warning flags. Expect dealers with this mindset to be either uninformed or purposely misleading. That was the point at which Dad and I started tuning out the dealer’s “helpful advice” altogether.

Even when interacting with helpful and well-informed dealers, we chose to make every calculation ourselves, just to be on the safe side. Every time we walked through an RV, we carried a tape measure and I made detailed notes on my smart phone. We searched the manufacturer websites and talked to others who owned the same model. When a specific question arose, Dad actually called the manufacturer and talked to the lead design engineer on that model (the one we ended up purchasing, as it turns out).

Though it took a long time and quite a few near-misses, we ended up buying from a wonderful dealership that we feel we can truly trust. Eagle Ridge RV in Lake Wales, Florida is a small dealership with only a handful of employees and a relatively small number of units, enabling them to provide us with nearly unparalleled service and advice. We are extremely happy with both our RV and our dealer. Take your time, refuse to yield to high-pressure tactics, and pursue any questions or concerns until you have a definitive and absolutely correct answer. Your family’s safety and happiness are well worth the effort.

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avatarAbout the Author:

Lisa is a full-time travel writer. She lives in an RV with her disabled father and writes about their experiences. Although she has no children of her own, Lisa loves being an Aunt to her own relatives and the children of all her friends. You can follow her adventures on her blog, Travel Confessions.

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