Weight distributing hitch

Tech > Weight distributing hitch


The simplest connection between tow vehicle and trailer is a weight-carrying hitch (WCH) system where the tongue weight of the trailer (typically be 10-15% of the trailer's total weight) is placed on the hitch and, by extension, the TV's rear axle. With large trailers come heavier tongues, and without a weight distributing hitch (WDH) system, the rear axle may become overloaded and the front axle underloaded:

Weight carrying hitch

WDH systems distribute the tongue weight over all of the axles in a rig:

Weight distributing hitch

The WDH ensures that proper steering control of the tow vehicle is maintained and that the rear axle is not loaded beyond its capacity.

Our system is the ProPride 3P. For more information, check out our 3P page.

A word about airbags

There's plenty of confusion about airbags and weight distribution.

The primary goal of a WDH is to distribute weight. A level tow vehicle is a by-product of a correct WDH setup.

By leveling the tow vehicle, airbags address the most visible symptom of tongue weight. However, they do nothing to redistribute the weight imposed by the trailer tongue to the front wheels of the tow vehicle.

Weight carrying hitch with

You may question the above statement. I did; I was one hundred percent confident it was true but didn't know how to prove it. I wanted to stand on firmer ground than the quicksand of "because I said so," so I conducted an experiment to prove my hypothesis: With tongue weight applied, leveling the tow vehicle will not redistribute weight to the front wheels.

I used one of my favourite camping toys: a radio controlled rock crawler.

Making tracks

It has a solid sprung axle and a point on the frame behind the axle to which I could clamp weight to model tongue weight. I just needed a small block of wood to replicate the airbags and a couple of scales.

Step 1 - unloaded and level

Airbag analog - undeployed

I set a board on each scale to accommodate the track of the test vehicle. I zeroed the scales, then set down the chassis on the boards. I placed the block of wood - the "airbag" - flat and undeployed so that its weight would be included. The frame sat level and I noted the weights: Front 1626 g | Rear 1315 g

Step 2 - loaded and sagging

Tongue weight - no airbag

I clamped a pair of locking pliers to the back of the frame. The "airbag" remained in place but still laid flat and undeployed. The "tongue" weight compressed the rear suspension completely and I noted the weights: Front 1414 g | Rear 2038 g

Step 3 - loaded and level

Set up - 1

With the pliers still locked to the back of the frame, I deployed the "airbag" between the frame and the axle, restoring the frame to the same level position as it enjoyed in step 1. I noted the weights: Front 1414 g | Rear 2037 g

Hypothesis proven. Leveling the frame had no effect. The 1 g difference (0.05%) in rear axle weights between steps 2 and 3 I put that down to a slight shift in the longitudinal position of the block of wood.

A good analog for an airbag. Yes, airbags hold air and wood holds, well, wood. Both accomplish the same purpose: supporting the rear of the frame and restoring the frame to level. The length of the block of wood is the same as the distance between the axle and the unloaded frame.

Now I know for sure... and you do too!

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