RV 101 Choosing the Right Tow Rig
Wed Feb 25, 2009
Author: Claire Rogers
Source: RV Extreme Magazine
Whether you buy a travel trailer or a toyhauler, towing an RV is much more involved than just hooking up and driving off into the sunset. While bigger RV's make hauling more demanding, the right hardware and your attention to weight are certain to resolve your towing issues.
All trailers put extra strain on a tow vehicle - extra weight on the axles, extra torsion on the transmission and extra load on the brakes and engine. For starters, your truck or SUV needs to come with a towing package which may include beefed-up suspension, lower axle ratios and pre-wiring for an after-market brake controller. Some other useful components may include additional engine cooling, transmission fluid cooling and a super-duty battery and alternator. Before you can mount a hitch, and with a ball, you’ll need the hitch receiver and a connector for the wiring harness. That’s just for starters.
Once connected to the hitch receiver, ball mount should position the ball so that it matches the height of the trailer coupler in order to keep the trailer leve while towing. Force the trailer to ride with the tongue high, and the weight shifts rearward aggravating trailer sway. Force the tongue down and you’ll put more weight on the tow vehicle’s rear axle, possibly exceeding the capacity and reducing your steering and braking power.
To get the hitch ball and coupler on the same level, measure the distance from the ground to the top of the truck’s hitch receiver tube. Remember that this will be closer to the ground once you’ve loaded it with the tongue weight. Next, measure the height of the lower edge of the coupler from the ground when the trailer is level. If these numbers are equal, you’re good. If they’re not, you’re normal. If the truck receiver is higher, find the “drop” by subtracting the second number from the first. If the truck is lower, subtract the first number from the second to find the “rise.”
Check your owner’s manual to determine the tow limits of your vehicle and to find out what is and what isn’t included in your tow package. Get the fully loaded trailer weight and tongue weight of your dream RV etched into your brain; you’ll need these number often. The tow vehicle needs to have the power to pull the weight of the trailer and a rear end to support the weight of the tongue. It also needs to have the right class hitch as well as a draw bar and hitch ball to match the hitch class.
HITCH CLASSES
The trailer tongue weight and gross trailer weight determine what class hitch you’ll need. Class I is rated to tow up to 2,000 pounds with no more than 200 pounds on the hitch. Class II totes as many as 3,500 pounds and 300 of them on the hitch.
As a weight carrying hitch, a class III is good for hauling 6,000 pounds, but this jumps to 10,000 pounds when the hitch is weight distributing or has load-leveling spring bars to leverage the tongue weight between all axles. Likewise, a class IV will give you up to 10,000 pounds of towing capability while supporting 1,000 pounds of front. Bump that up to 14,000 and 1,400 pounds for a weight distribution set up. Class V hitch capacity, without weight distribution, is 12,000 and 1,200 pounds and with a weight distribution system increases to 17,000 pounds gross trailer weight and 1,700 pounds of tongue weight.
WEIGHT DISTRIBUTION
Clearly the weight distributing hitch has some advantages, but how does it work and do you need it? Weight distributing hitches are an engineering advancement that makes towing heavier trailers much safer. They are recommended for all but the lightest class of trailer, so anything over 2,000 pounds should use a weight distribution system.
Simply put, a weight distribution hitch used two torsion bars that run on either side of the hitch. Once connected on either side of the trailer tongues these bars force the front end of the tow vehicle downward as the weight increases. The result is a tow vehicle with all four wheels firmly planted on the ground. Going without a weight distribution system is possible as long as your still within the towing limit of your hitch, but you may need a sitter rear suspension to better handle the tongue weight. This means you’ll likely have less control and enjoy a hard ride when you’re not towing.
SWAY CONTROL
Sway control is another engineering feat that makes towing safer. The two main methods are friction, which dampens sway once it has already started, and cam action, which resists sway in the first place. Again, the heavier the trailer, the more likely you are to need sway control. Crosswinds, traffic turbulence and improper weight distribution, both side-to-side and front-to-back, are just some of the factors that contribute to trailer sway.
Some of the biggest towing headaches have been solved with creative engineering. Done right, towing even big rigs is much safer than it used to be. Now check that your indicator lights and brakes are properly operating. Add wide-angle mirrors and keep that RV in sight as you’re traveling down the road.
