When towing a trailer with a standard ball mount, all the trailer's tongue weight is transferred to the tow vehicle. Since the trailer hitch is attached to the vehicle frame, the additional weight in the rear will lower the back end of the vehicle while raising the front end. This means that the rear axle will be handling not only the trailer tongue weight but the additional load of the weight being transferred from the front axle. Less weight on the front axle can cause diminished performance, decreases in steering, traction and stopping and simultaneously increase trailer sway.
Weight distribution hitches add spring bars to the hitch system that apply leverage between the tow vehicle and the trailer. This leverage transfers the load sitting on the rear of the vehicle to all the axles of the vehicle and trailer. With the trailer tongue and rear cargo load distributed between the axles, the vehicle is leveled off and performance is greatly improved. Weight distributing systems should be used any time the trailer weighs more than 50 percent of the vehicle's weight.
A weight distribution hitch will have two weight ratings, the gross trailer weight (GTW) and tongue weight (TW). The GTW capacity of the weight distribution system must exceed or match the loaded weight of the trailer. The TW rating listed on weight distributing hitches refers to trailer tongue weight plus the weight of the vehicle's cargo behind the rear axle. It is important to match the weight distribution system tongue weight to your specific application. Using spring bars with a 1,000 lb TW capacity on a trailer with 400 lb of tongue weight while 100 lbs of cargo is in the trunk (hitch weight = 500 lbs total) can lead to erratic weight distributing performance. Looking at it the other way, if a weight distribution system has 500 lb TW capacity with a 1,000 lbs of weight, the system would be ineffective.
Tongue Weight (for Weight Distribution) = trailer tongue weight + vehicle cargo load behind rear axle
We offer a tongue weight scale which quickly, easily and very accurately allows you to get the weight of the trailer tongue.
Tongue weight on smaller trailers can be measured with a bathroom scale and a box. On a level surface, place the coupler of the loaded trailer on the scale at normal towing height (Figure A). For heavier tongue weights, use the method diagrammed below (Figure B).
In addition to the Class III, IV or V trailer hitch on the vehicle, the weight distribution system is made up of the ball mount, spring bars (also called load bars or equalizing bars), and trailer-mounted brackets. The ball mount is composed of two pieces: the shank, which slides into the trailer hitch, and the ball platform, which is referred to as the weight distribution head. The shank is available in different lengths with different drops and rises to allow for various trailer heights.
The trailer hitch attaches to the frame underneath the vehicle and provides the 2" x 2" (or 2-1/2" x 2-1/2") receiver opening that the weight distribution shank slides into. Trailer hitches are categorized by classes based on weight-carrying capabilities. A trailer hitch must be classified as Class III, IV or V to be considered for a weight distribution system. A few Class III hitches are designed NOT to be used with a weight distribution system; therefore, always check the weight capacity label that is on the trailer hitch. This sticker lists two capacities, weight carrying and weight distributing. If nothing is listed for weight distributing, then a weight distribution system cannot be used.
The weight distributing shank is the piece that slides into the hitch and provides an attachment point for the head. The shank is available in many different lengths, drops and rises. For easier and safer towing, it is necessary to have the trailer at a level height when it is hooked up to the hitch ball. The shank will allow you to do this. View our FAQ page for more information on choosing the correct ball mount height. You can also view all our available weight distributing shanks.
The head unit holds the spring bars, provides a platform for the hitch ball, and attaches to the weight distributing shank. Weight distribution heads have a few different features to point out. The tilting mechanism, which fine tunes the weight distribution set up, is available in two different styles. The High Performance or Heavy Duty systems allow the tilt to be easily adjusted with serrated washers on the outside of the shank. The standard style systems use a pin with washers placed in between the head and the shank to control the tilt. Accessing the pin and washers can get quite tedious. However, this typically has to be done only upon initial setup or when the trailer load changes enough to alter the height of the coupler.
The head can also have built-in platforms to allow for friction style sway control attachments. Many will offer only a right side attachment while some will have dual platforms which will be necessary for larger trailers (depending on the style of sway control used). The head is also made to accept different types of spring bars, round or trunnion. The round and trunnion terms refer to the end of the bars that attach to the weight distributing head. The round style bars slide up into the head and are held in place with clips. The trunnion style bars slide into the head from the side or back. The trunnion style of weight distribution is more heavy duty and can handle trailers of greater weight.
As previously explained, there are two types of spring bars - round and trunnion - referring to the end of the bars that attach to the weight distributing head. The round style bars slide up into the head and are held in place with clips. The trunnion style bars slide into the head from the side or back. Spring bars can also vary on the end opposite the trunnion or round bar end. The latest style from Draw-Tite, Hidden Hitch and Reese include built-in cams which are designed for use with Dual Cam Sway Control. The Draw-Tite, Hidden Hitch and Reese spring bars are also tapered on every side providing the ultimate in spring bar flex. The more the spring bar flexes, the more the weight distribution system will be working. When spring bars do not flex enough, the system can essentially turn off.
Chain links are used to connect the spring bars to the trailer mounted brackets. The most common style is a snap-up uplift bracket. It lowers to grab the chain, then raises and snaps into position. The number of chain links is used to help determine the proper amount of tension to support the load. Space saving designs are also available that clamp to the trailer frame, or bolt to the side of the trailer frame.
A popular accessory to the weight distribution system is the sway control. Trailer sway can be caused by crosswinds, poor trailer loading (load too far back), or inadequate spring bar tension. The use of a weight distributing hitch by itself will help improve trailer sway, but some additional products can help eliminate it. Trailer sway can be controlled with three different types of systems. NOTE: Friction sway controls should be removed in inclement weather and when backing up.
Independent friction controls have been around the longest. One side of the mechanism attaches to the trailer and the other to the weight distribution head. The steel bar with friction pad is used to slow down trailer sway. One slide bar friction control can be used for trailers up to 6,000 lbs Anything over 6,000 lbs, and less than 10,000 lbs, will require two controls. Aside from over 6,000 lbs, if the trailer is 26' or longer, you will want to use 2 sway controls. Independent friction controls can also be used without a weight distribution system. Over or under tightening the sliding mechanism can render the system ineffective. [Part #3400]
Dependent sway controls are built in to weight distribution systems. They rely on the downward force of the spring bar to apply frictional resistance to brackets on the trailer tongue to combat trailer sway. This style is more consistent than the independent friction style, is easier to hook up, and over or under tightening is not a problem. This system is the only one approved for trailers with surge (hydraulic) brakes. [Part #RP66158]
Active sway controls also require a weight distribution system. An example of active sway controls is the Dual Cam System from Draw-Tite, Hidden Hitch and Reese which proactively and aggressively resist the start of sway by forcing the vehicle and trailer to ride in straight line. In tight turns the dual cam lifts the outside spring bar which increases towing performance by leaning the tow vehicle and trailer into the turn. The dual cam system can only work with weight distribution systems that have cams built into the spring bars. [Part #RP26002, and 26001]
Weight distribution systems are available in many styles which differ from the type of spring bar to the type of ball platform to the way optional sway controls are integrated. Each of the different styles are then broken down to accommodate trailers of different weights.
The best in weight distributing systems and the best in trailer sway control has been combined in the Strait-Line system. The High Performance trunnion weight distributing hitch offers spring bars with the most flex ensuring the load is always evenly distributed, even on rough terrain. The serrated washers on the weight distribution head make it easy to fine tune installation of the system, while the Dual Cam system keeps the trailer in a straight line behind the tow vehicle. When only the best will do, then it has to be the Strait-Line Weight Distributing Hitch by Draw-Tite, Hidden Hitch and Reese.
When trailer sway is not a problem, the High Performance Weight Distribution System, used in the Strait-Line system, is available by itself. Independent friction control or the dual cam sway control can always be added later if it is necessary. The High Performance Trunnion style system offers the most spring bar flex and the easiest to tilt head.
The Heavy Duty Round Bar weight distribution system was developed by Reese and is now carried by Draw-Tite and Hidden Hitch. The system uses spring bars that are tapered like the trunnion bars to provide excellent flex. Aside from the way the bars attach to the head, the other difference between the trunnion style is the rotating washer design used to control the tilt of the head. The system will work with an independent friction sway control while the spring bars include the cams to work with the Dual Cam system.
The Reese SC with dependent sway control maintains 6 points of friction to control trailer sway and utilizes easy-to-install clamp-on trailer brackets. The adjustable brackets do have a wider mounting range as they can be installed between 17" and 30" (depending on weight capacity) but the biggest improvement is in the design of the spring bars. The Reese SC utilizes more tappered trunnion bars offering superior spring bar flex and therefore superior performance. The system will also work on boat trailers with surge (hydraulic) brakes.
For smaller and lighter trailers, such as pop-up campers, there are other options still available. The single spring bar systems are rated to match trailers that weigh up to 4,000 lbs The 3205 is designed for trailers with a straight pole tongue while the 3204 is for A-frame trailers. The hitch head will accept left or right hand friction style sway controls. A two arm weight distribution style is also available with dependent sway control. These systems are designed for trailers that weigh up to 3,500 lbs with 300 lbs of tongue weight. Part # 66041 is designed especially for Fleetwood and Coleman pop-up campers.
Pole Tongue Adapter - for use on trailers that do not have an A-frame tongue. The pole tongue adapter clamps around the straight or pole tongue of the trailer and provides hook-up locations for the uplift brackets of the weight distribution system.
Weight Distribution Clamp On Chain Hanger Kit - a slimmer uplift bracket designed to take up less space on the trailer tongue and installs without drilling. #RP58306
Weight Distribution Bolt On Hanger Kit - does not take up any space on the top of the trailer frame allowing plenty of room for toolboxes, propane tanks, winches, batteries or anything else. #RP58305
Hitch Balls - sold separately on all weight distribution systems.
Weight Distribution Parts- Replacement parts and accessories are available for most of the weight distribution systems. etrailer.com offers replacement brackets, head assemblies, replacement spring bars and much more.
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I am very impressed. I ordered my sway control adapter on Sunday night and recieved it on Wensday morning by UPS ground the same week. Great job! Thanks, Gene
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