Hitching Up
Joel Donaldson
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Trailers are available in two different designs: a travel trailer that’s coupled to the rear of the tow vehicle by a conventional hitch ball, and a fifth-wheel trailer that utilizes a fifth-wheel (or gooseneck) hitch mounted in the truck bed, centered over the rear axle. The hitching methods are as different as the trailers and require specific knowledge by the installer and trailer owner.
Conventional Hitches
All hitches are rated by their respective manufacturers to safely handle up to a specific gross vehicle weight (gvw), which is the weight of the trailer with full water and LP-gas cylinders and all supplies aboard. Several weight classes exist for hitches designed for towing conventional travel trailers.
Weight-carrying hitches are intended for lighter trailers because the entire trailer’s hitch weight is carried on the ball and transferred to the rear axle of the tow vehicle, whereas weight-distributing hitches are designed to distribute the trailer’s hitch weight to all axles of the tow vehicle and trailer, making larger, heavier trailers with considerably higher hitch weights towable without destabilizing the tow vehicle.
A travel trailer with ideal weight distribution will have a minimum hitch weight of about 12 percent of the gross weight, and the maximum can range upward to about 15 percent, provided it does not violate the rating of the hitch.
Except for the lightest folding trailers, hitches rated Class II and higher are used for recreational towing, and they use a receiver bolted to the tow vehicle’s frame. The hitch receiver — which may have box dimensions of 11?4 inches square, 2 inches square or 21?2 inches square, with the larger boxes for higher load ratings — accepts a slide-in ball mount (or draw bar), which is secured with a pin.
Besides serving as the trailer/receiver attachment point, the ball mount also is used in varying heights (known as “drop”) to couple the trailer in a level fashion (frame parallel to the road surface), which is desirable for best stability and trailer-brake performance. Some ball mounts are fixed, while others are adjustable.Ball mounts used for weight-carrying hitches are quite different than those used for weight-distributing. The need for weight-distributing hitches varies with tow-vehicle type and trailer weight. A trailer with 350 pounds of hitch weight may present no challenge for a stiffly sprung, long-wheelbase HD pickup, while it may destabilize a softly sprung compact SUV. In general, a weight-distributing hitch will improve stability in most situations because weight resting on a hitch ball (when a weight-carrying hitch is used) loads the rear axle excessively by placing all of the hitch weight on that axle in addition to weight that is transferred from the front axle to the rear in a seesaw lever action.
Because many receivers are usable in either weight-carrying or weight-distributing configurations, depending on the ball mount, the receiver manufacturer may list both ratings.
Weight-distributing hitches should be used in many weight situations of Class II, and in most situations of Class III and above. Unlike their weight-carrying counterparts, these hitches typically use a much heavier ball mount (that’s height-adjustable), plus a pair of spring bars that provide the leverage needed to distribute weight fore and aft.
Hitch Adjustment
After having a weight-distributing hitch of proper weight rating installed, owners may take the rest for granted. This can be a costly error because an improperly adjusted weight-distributing hitch can contribute to trailer sway, which is a very undesirable, and unsafe, handling trait.
The keys to happy towing are proper hitch-ball height and proper tension on the spring bars. When all aspects are correct, the tow vehicle and the trailer are at the proper ride height, which in most cases is level. One exception will be described later. Proper hitch adjustment helps prevent rear-axle overloading and improves braking and steering response.
Evaluating the proper adjustment of a weight-distributing hitch is relatively simple: The tow vehicle should maintain the same attitude before hitching that it does after hitching, measured at reference points at the front and rear bumpers or wheel wells. If it is level before hitching, it should be level afterward, although slightly lower due to the addition of hitch weight. A level attitude means the adequate load has been placed on the spring bars to distribute portions of the hitch weight equally to the front and rear axles. If the rear of the tow vehicle sags after hitching, then the spring-bar loading isn’t adequate.
The exception to level attitude: If the tow vehicle is a stiffly sprung pickup and the rear of the truck is higher than the front, that attitude should be maintained after hitching. Such trucks often will carry heavy loads without the need for weight-distributing hitches and without sagging. But care must be exercised here. Although the truck may not look like it’s sagging visually, the hitch weight carried by the rear axle may still create an unstable situation.
If the trailer is not level after the spring bars have been adjusted to create the proper tow-vehicle attitude, then the ball height should be corrected.
Trailer sway can be a problem if trailer balance or hitch adjustment are not correct because the trailer exerts steering leverage on the tow vehicle by virtue of being connected to the tow vehicle 3 or 4 feet behind the rear axle. With correct hitching, trailer balance may be a problem if the hitch weight is less than 10 percent of gross weight. It should be more than 10 percent (we recommend a minimum of 12 percent) for best stability.
Even with a well-balanced trailer and a properly adjusted hitch, use of a sway-control device is highly recommended. Often called sway bars (not to be confused with anti-roll bars fitted to axles of tow vehicles), sway-control devices are designed to damp rotation of the coupler on the hitch ball. They improve the handling characteristics of the trailer/tow vehicle combination whether the hitch method is weight-carrying or weight-distributing.
Sway-control devices are available in two different configurations, the most popular of which is one that employs a steel bar, attached to the ball mount, that is encased in a rail or tube attached to a small ball on the trailer A-frame. Inside the rail or tube is friction material that is clamped against the steel bar. Any pivoting of the trailer coupler on the bar causes the bar to slide within the rail, creating drag and damping sway. On larger trailers, it’s often possible to use a pair of friction-type units for additional sway control.
One popular hitch, the Equal-i-zer, includes a friction feature in the hitch design in that the tips of spring bars create friction on trailer-frame brackets. Cam-type sway units work by modifying the operation of the spring bars on a weight-distributing hitch. As the trailer turns, a cam increases the tension on one of the bars, creating a force that tends to pull the trailer back into a straight line. The harder the trailer turns, the stronger this self-centering force becomes. Since this scheme relies on spring-bar tension, it’s generally most effective on trailers with relatively high hitch weights (e.g., trailers requiring considerable spring-bar tension).
The Hensley Arrow and PullRite hitch systems offer different approaches to controlling sway. The Hensley unit prevents sway through use of trapezoidal hitch linkages that make the tow vehicle and trailer act as a single unit, with no pivoting of the coupler on the ball unless the tow vehicle turns. Thus, during typical highway travel the tow vehicle and trailer are connected as non-articulated vehicles, and tend to function as a single unit. Even so, there is no restriction on the tow vehicle’s capability for turns.
The PullRite, in effect, moves the hitch-pivot point to a location immediately aft of the tow vehicle’s rear axle, dramatically reducing the leverage the trailer can exert on the tow vehicle.
Fifth-Wheel Hitches
Fifth-wheel towing is a different story altogether. The trailer’s kingpin serves as the pivot point for the fifth-wheel hitch, which is centered slightly ahead or over the truck’s rear axle. The trailer’s kingpin slides into the hitch saddle, where it is secured by latching jaws or some other mechanism. This saddle is attached to a support base, which transfers the towing forces to the truck frame.
The design prevents the trailer from having any steering effect on the tow vehicle, and is what gives fifth-wheel trailers such good road manners. Wind gusts and road irregularities have little or no effect on tow-vehicle stability.
Most hitches are secured to the bed with a pair of mounting rails, while other underbed systems leave the truck bed flat after the hitch is removed.
Until recently, fifth-wheel hitches have been strictly aftermarket add-ons. But Ford and GM upped the ante with the availability of a factory-installed fifth-wheel (and gooseneck) hitch, providing clean installation and a factory warranty. The trailer’s electrical connection has been mounted into the side of the bed for added convenience.
Most removable aftermarket systems use permanently mounted rails with pins to secure the hitch saddle. The underbed style of the fifth-wheel-hitch mount is completely different in that the entire hitch mechanism is removed by simply pulling a lever in the wheel well. PullRite also uses an underbed system with removable connection pins. Some systems, such as the B&W Turnover Ball and Companion, allow the hitch saddle and support base to be removed separately, making it easier on the back when lifting the hardware.
Many fifth-wheel hitches are mounted so they tilt fore and aft; however, having only the fore-and-aft pivot restricts side-to-side movement. Some hitches have heads that pivot in multiple directions, allowing the pinbox to move in any direction with respect to the pickup, while still maintaining a tight mechanical connection. This also makes it easier to hitch or unhitch the trailer on uneven ground.
Another strategy for improving trailer-truck flexibility involves the use of air springs as part of the hitch design. Typically, the hitch is suspended on multiple bladder-type air bags, which support most of the trailer’s kingpin weight. Aside from providing considerable articulation, these bags are also capable of smoothing out much of the road shocks and vibration that would otherwise be transmitted from the trailer to the tow vehicle. Adjustments to the system can be accomplished by varying the amount of air pressure in the bags.
Other suspension-type hitches use a hinged pivot arm and a single airbag setup or a rubber spring in shear to provide truck-to-trailer impact damping while the hitch-saddle mechanism provides the side- and fore/aft head tilting.
Shortbed pickups are now more popular than ever, particularly among extended-cab models. However, a short bed often causes complications when using the truck for towing a fifth-wheel because the proper hitch-mounting location is far enough forward to cause trailer-to-cab collisions during sharp turns. Installing an extended pinbox provides a workable solution with smaller trailers with modest pin weights; however, owners should first check with the pinbox manufacturer before adding any extension.
One solution is a conventional hitch that can be manually unlocked and moved aft on a special set of rails before making tight turns. PullRite offers a hitch that performs this motion automatically, returning to the forward-towing position after the turn is completed. Rearward travel can be as much as 22 inches for some models, which is generally adequate for accommodating 102-inch-wide trailers. Turns as tight as 90 degrees are even possible.
Some companies offer manually moving hitches to accommodate sharp turns, but the owner is responsible for unlatching the mechanism. Another system, the Reese Sidewinder, uses a special pin box that automatically handles clearance problems.
Maximum weight ratings for fifth-wheel hitches range up to 25,500 pounds gross weight, with as much as 25 percent of it on the hitch (most fivers have 20 percent hitch weight or less), and it’s best to choose a unit that not only will handle the trailer it will be used to tow, but also any possibility of a larger trailer, although a higher-rated hitch will cost more and will be slightly heavier.
Whether towing a conventional trailer or a fifth-wheel, the use of a properly rated hitch, adjusted correctly, will aid in creating a safer and more manageable towing experience.
