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Battle of the Bulge

May 17, 2019
Battle of the Bulge

How much do you really know about the loaded weight of your van?

In other words, if your van was loaded up for a holiday, water tanks and gas cylinders full, and you put it on a weigh-bridge, its coupling supported by the jockey wheel, what would the ticket say? In kilograms, would the final number be equal to or less than the ATM engraved on the van’s compliance plate?


Alphabet Soup

But why, you might ask, should I pay attention to this number? An in-depth explanation would have to take into account ball weight and Gross Trailer Mass (GTM).

GTM is the maximum weight that can be transmitted to the ground by the van’s tyres – think of it as the loaded weight of the van minus the weight supported by the jockey wheel or tow bar. As with ATM, GTM must never be exceeded. The same goes for the tow ball maximum set by your tow vehicle’s manufacturer.

Say your van has an ATM of 2500 kg and, when loaded, the ball weight is 240 kg. This means the weight being transmitted to the ground (the GTM) must not exceed 2260 kg.

Crucial components of the trailer, especially the suspension and the axle(s), are rated by their manufacturers to carry a certain amount of weight. In the above example, these components should be rated to carry at least 2260 kg.

The trailer’s manufacturer has taken these ratings into account when setting the overall ATM. Exceeding these weights, therefore, puts your trailer, your life and the lives of your passengers and other motorists, at risk. Is that generator you could perhaps do without really that important?

There’s a slight wrinkle worth discussing. Depending on the ratings of the axle(s) and suspension, it may be possible for the van’s manufacturer to increase the ATM in order to provide more payload capacity. It’s not unheard of, also, for a caravan manufacturer to ‘de-rate’ a van’s ATM to make it appeal to owners of certain vehicles. This is not unethical – provided after the ‘de-rating’ the van retains a realistic payload capacity.

If you’ve overloaded your van, there’s a good chance you’ve also exceeded your tow vehicle’s legal (and safe) ability to haul it. Let’s face it: many of us match the ATM of our vans to our vehicle’s towing capacity. If you have a 2500 kg-capable Prado, for example, you might have shopped for a van with an ATM of 2500 kg. Guess what? If the van weighs 2501 kg, that Prado is now towing illegally.


Weighing it up

The common advice to ensure your van is not overweight is to visit a weigh-bridge. I believe this remains sound advice. But it does mean the trip to the weigh-bridge could be illegal.

Before heading off to the weigh-bridge, therefore, run some basic numbers. An exercise I’ve conducted before was to individually weigh each item in my van. It took some time but the results were eye-opening.

Now knowing that six beers weigh roughly 3.5 kg and that our family’s sleeping bags have a combined weight of 10 kg, for example, means I can make some educated guesses each time I load up. Obviously, I take into account the weight of the water and gas, too.

The bottom line: there are very good reasons not to overload your van. You can bet that should the worst happen, the police have their ways of determining whether or not you’ve done so. And I suspect they would take a very dim view if you have.