Weight Distribution Hitch

How They Work

Weight distribution hitches add spring bars to the hitch system. These are used to apply leverage between the tow auto and also the trailer. This leverage transfers the load sitting on the rear of the truck to all the axles of the truck and trailer. With the trailer tongue and its weight & cargo distributed between the axles, the vehicle is leveled off and performance is greatly increased while increasing safety.

When To Use Them

Weight distributing systems ought to be used any time the trailer weighs more than 50% of the tow vehicle's weight.

What Size To Get

A weight distribution hitch will have two weight ratings, the gross trailer weight (GTW) and tongue weight (TW). The GTW capability of the weight distribution system should exceed or match the loaded weight of the trailer. The TW rating listed on weight distributing hitches refers to trailer tongue weight and the tow vehicle's cargo weight the rear of the rear axle. It's necessary to match the load distribution system tongue weight to your specific vehicle & trailer combo.

What's the Gross Trailer Weight (GTW)?

The load of the trailer fully loaded and ready to tow. GTW is found by means of driving the fully loaded trailer onto a vehicle scale.
 
What is the Tongue Weight (TW)?

The tongue is the force of the trailer AND the cargo weight behind the rear axle of your tow vehicle. Trailer tongue weight is the downward force pushing on the hitch ball through the trailer coupler. Usually it's about 10 to 15 % of the GTW.

...So the TW (Tongue Weight) = trailer tongue weight + tow vehicle cargo load behind the back axle of your tow vehicle.

Figuring the TW for a small trailer:

This may be done through the use of a bathroom scale. On a level surface, place the coupler of the loaded trailer on the scale at normal towing height.

Weight Distribution Components:

In addition to the class III, IV, or V trailer hitch on the vehicle, the weight distribution system is made up of the ballmount, spring bars (a.k.a. load bars or equalizing bars), and trailer mounted brackets. The ballmount is made up 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 different trailer heights.

Weight Distribution System

1. Hitch Assembly: The trailer hitch attaches to the frame underneath the vehicle and provides the receiver opening that the weight distribution shank slides into.

Trailer hitches are divided up into different classes based on weight carrying capabilities. A trailer hitch needs to 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 can not be used.

2. Shank Assembly: 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.

3. Head Assembly: The head unit holds the spring bars, provides a platform for the hitch ball, and attaches to the weight distributing shank.

4. Spring Bar Assembly: There are two types of spring bars - round and trunnion - which refer to the end of the bars that attach to the weight distributing head.

5. Chain and Bracket Assembly: Chain links are used to connect the spring bars to the trailer mounted brackets.

Sway Control:
A popular accessory to the weight distribution system is the sway control. Trailer sway can be caused by cross winds, poor trailer loading (load too far back), or not enough 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:

Friction Control
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 2 controls. Independent friction controls can also be used without a weight distribution system.

Dependant
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.

Active
Active sway controls also require a weight distribution system. They resist the start of sway by forcing the vehicle and trailer to ride in straight line. In tight turns it leans the tow vehicle and trailer into the turn. These are dual cam systems and can only work with weight distribution systems that have cams built into the spring bars.