The Black Art of Towing Part Two - The Weight Distribution System

So, what is a weight distribution system and do I really need one?

Well, it's a method of spreading the weight of the trailer's tongue around a bit and yes, I really do need one. 

If I were to hitch the trailer to my car without weight distribution then the entire 1000 lbs or so of the trailer's tongue weight would be resting at a point some three to four feet behind the rear axle, putting all the weight on that rear axle. Quite apart from exceeding the axle's weight limit, the back of the car would be almost on the ground and the front would be pointing skywards. Even if I could stiffen up the rear suspension to stop the back of the car from dropping so low, the front axle, which is the drive and steering axle, just would not function as it should.

What's required, then, is a set up where I can push that load forward so it can be spread across both front and rear axles, and for good measure transfer some of it back to the trailer itself. Fortunately, there are weight distribution systems to do just that.

Above is a photograph of the system we use, shown without the trailer. The hitch head is to the right, with the ball clearly visible. The two spring bars fit into the bottom of the head and provide the "lift", whilst the chains on the end of the spring bars attach to two hooks which are fitted to the A-Frame of the trailer. This is a relatively unsophisticated system and deals only with weight distribution; there are others like the Hensley or the Propride PPP that deal with both weight and sway. However, the Eaz-Lift is lighter and cheaper and for us, seems to do the job perfectly well. I'll deal with the sway aspects of the hitch in another blog entry.

The next photograph above shows the system fitted to our trailer, the spring bars are under tension and providing lift. Also pictured is one of the sway control bars and the safety chains, neither of which has any function to support weight distribution system but are both very important in their own right; more of that later.

The picture also shows the hitch head very close to the rear of the car's bumper. When not under tension, the hitch head sits a few inches lower and a few inches away from the bumper, but the action of the spring bars is enough to lift the trailer's tongue (all 1000 lbs of it) up and push it forward, clearing demonstrating the lift and weight forward transfer properties of the system.

The method to attain the tension on the system is a process that I've never been comfortable with but it is the recognised way of doing things. Firstly I back the car up to the trailer and using the trailer's jack, I lower the ball receiver onto the ball and lock it into position. Then I use the jack to lift the tongue of the trailer and the car, up to a point where the car's rear wheels are just about to leave the ground. The trailer's coupler is holding the weight of the car and it's being supported by the hitch receiver! I fit the spring bars into the hitch head and attach the chains to the hooks on the trailer's A-Frame, to a point on the chain that was pre-determined by our hitch riggers, thus establishing the correct amount of lift and forward weight transfer. Then I lower the trailer and car by retracting the trailer's jack. As the weight is lowered, the spring bars take up the tension and start the lift and weight transfer. Once the jack is off the ground and the car is settled on its suspension, it looks like the picture above, with the hitch head up and forward rather than down and back as you might expect.

It's now that about two-thirds of the tongue weight is being transferred to the car and about a third back to the axles of the trailer. If the hitch is rigged correctly then the weight transferred to the front axle of the car should keep it in proportion to the weight on the rear axles and the car and trailer should appear level, or thereabouts. The weight on that front axle needs to be in proportion to the weight on the rear axle for it to function properly and that's the aim of the weight distribution system.

Now we see the whole combination sat level on the road (in Bayfield, Ontario), just to show how it all works.

If you're wondering about the principles of weight transfer, I've best heard it explained as being like a wheelbarrow. You couldn't pick up a wheel barrow full of bricks just by grabbing the barrow bit, but by using the arms of the barrow as a lever and the axle of the wheel as a fulcrum, it's easy to lift up. The levers on the weight distribution system are the wheel barrow's handles, the fulcrum for the lever is the point(s) at which the hitch receiver is bolted to the car and your feet are the trailer wheels. I think that's easy to understand and sums it up nicely!

In assessing if a tow vehicle will work, rather than fixating on the manufacturer's tow rating, you should be looking at what load the axles and the tires will take. When you're doing that, you have to consider the two-thirds of the trailer's tongue weight that is now spread across your car because it will affect what you can carry. Fortunately, that 'payload' figure is quite generous for the Sienna so I do have the ability to take passengers and luggage without overloading the axles; it's not the same for all prospective tow vehicles, though, and sometimes the much vaunted pick up truck will be tight on what the axles can handle when loaded and hitched.

One of the less well documented advantages of having weight distribution is that it really makes the two parts, the car and the trailer, act as one with the weight spread over all four axles. The trailer is responsive to the movements of the car and vice-versa, and when towing something that weighs three and a half tons, any advantage you can get is always very welcome.

The Toadmobile couldn't tow this trailer without weight distribution, but some vehicles are sufficiently strongly built that you could just hang the trailer on the hitch and drive off. Similarly, I could tow a light weight trailer without weight distribution. However, without the system, all the weight of the trailer is weighing on the rear axle, taking weight from the steering axle at the front, which is never good. It matters not how big your tow vehicle or how small your trailer, weight distribution will always help the towing process.

I have to point out here that I didn't set the weight distribution system up myself, although it's a reasonably easy thing to do. I prefer to use the services of an expert, for us Can Am RV, and know that everything will work as intended.

My next blog entry will be about the hitch receiver, the bit bolted onto the car. That's as critical as the weight distribution system and needs to be set up correctly for the weight distribution to work effectively. So, look out for the next instalment in The Black Art of Towing, coming to a device near you....