ADVICE - What is a Weight Distribution Hitch

Words & Photos: Courtesy of  PracticalMotoring.com.au

When it comes to towing heavy loads, like a large caravan or boat, a weight distribution hitch can help to stabilise your trailer and towing vehicle. But what is a weight distribution hitch and how does it work?

There are a lot of myths around weight distribution hitches, so let’s start by dealing with the big one - a weight distribution hitch allows you to tow more because it transfers weight. It doesn’t; fitting a weight distribution hitch DOES NOT allow you to tow more than your vehicle’s specified braked limit.

What happens when you connect a trailer?

When you hook up a trailer or caravan to your towing vehicle, weight is transferred onto the towbar - this is referred to as the towball download. If you’re towing a trailer at your vehicle’s maximum allowed towing capacity, you’ll have a lot of weight bearing down on the towbar, which in turn puts pressure on the rear axle, causing the vehicle to ride with a rear-down, nose-up attitude and the trailer to be dragged in a nose-down and rear-up fashion.

This generally becomes an issue when what you’re towing weighs around 50 per cent of your vehicle’s weight. But a poorly loaded trailer weighing much less than that can also cause issues with the towing vehicle. For example, if your 4x4 has a towball download rating of 350kg, but the towball download being applied by the trailer - because of poor loading - is 400kg, then you have a problem.

Why is it bad to overload the towball?

Because, as mentioned, you get an unbalanced towing profile which can cause all sorts of problems, from reduced effectiveness of your vehicle’s braking and steering, along with compromised vision when the vehicle’s in a nose-up, tail-down stance. Another byproduct of an overloaded towball is increased and unnecessary wear and tear on your vehicle, especially the rear suspension and tyres.

Worst of all, an unbalanced towing profile can also increase the risk of trailer sway, which is when your trailer begins to wag from side to side. This is both frightening for the driver and potentially dangerous.

How do I weigh the towball weight of my trailer?

There are a couple of ways to do this.

You can use the bathroom scale method, which I’m not a fan of because there’s too much fiddling around and you can’t always be sure of the accuracy. The best way is to purchase a dedicated ball weight scale. To get an accurate measurement, you'll need to weigh your trailer or caravan’s towball download when empty and again when loaded, as if you were heading away with it.

It’s recommended you do this well before heading off with the trailer to ensure you’ve got plenty of time to make adjustments, ie. repack or remove gear, as needed, rather than fussing around doing this at the last minute.

How do I know I need a weight distribution hitch?

Ideally, you’ll be considering a weight distribution hitch if your trailer, when loaded, is around half the weight of your towing vehicle. Any more than that and you will need a weight distribution hitch for trailer stability.

Can all towbars take a weight distribution hitch?

No. You need to check with the manufacturer of your vehicle if it’s a factory fitted towbar, or the towbar maker if an aftermarket addition. Some simply aren’t designed to incorporate a weight distribution hitch.

Also, if you aren’t using a factory fitted towbar, you need to check what the manufacturer says about maximum braked towing capacity. Many vehicle manufacturers list a reduced amount when not using a factory-approved towbar.

What is a weight distribution hitch?

These are a set of spring bars that are fitted to the caravan or trailer’s drawbar and the towing vehicle’s hitch. Once fitted and adjusted, they create a lever effect that spreads the weight (but not the mass) being applied to the towbar evenly across the axles of your tow vehicle and trailer.

This means that the weights being applied remain identical, so, if the towball download was 300kg to begin with, it will still be 300kg after the weight distribution hitch has been fitted. The weight distribution hitch spreads the applied weight but doesn’t increase the mass.

By spreading the weight, your tow vehicle and trailer should sit level and thus reduce the risk of trailer sway, ensuring you have proper control over your towing vehicle. It’s a clever system and the action of how it works is often likened to raising a wheelbarrow via the handles or pushing down on a set of scales while standing behind it.

So, a weight distribution hitch solves all problems?

Not quite. While your vehicle and trailer might be sitting level and sway potential is reduced with a weight distribution hitch fitted, it’s not eliminated. And that’s why many people also fit a sway controller, too, but we’ll look at that in another article.

A minor negative byproduct of fitting a weight distribution hitch is that the bars can reduce the turning circle of your rig.

Want to know more?

The aim of this article is to dispel the myth that fitting a weight distribution hitch allows you to tow more. It doesn’t. It just ensures the weight you’re towing is evenly spread across the trailer and towing vehicle.

There are different types and brands of weight distribution hitch available, and some are designed for certain types of drawbar. Also, depending on the height of your vehicle and trailer, you may need to fit an adjustable towbar. Again, you’ll need to check with your vehicle manufacturer to see if this affects the maximum braked towing capacity of your vehicle.

As with any other element of vehicle – or in this case, trailer – modification, if you’re unsure what you’re doing, seek professional advice or entrust fitting to an expert. The implications of a botched DIY job can be very serious.