Towing Basics

All vehicles, caravans and campers have a certain weight they can safely – and legally – weigh. All components of every vehicle, camper and caravan is is engineered to withstand a certain weight, with a safety margin, before it fails. These legal weights cover several different parts of the rigs – their empty weight, how much load they can take, their total weight, and more.

When a vehicle or caravan manufacturer specifies weights, it becomes a legal requirement for the driver to adhere to this. As soon as you wheel the rig out on the road, you’re in charge of it and it is assumed you have taken adequate steps to ensure your rig is safe and legal. If you are randomly weighed by the state roads authorities or have a crash due to overloading, you can’t claim you didn’t know that the vehicle or van was overloaded. You’re supposed to check. And your insurance may be voided if you didn’t.

Generally, the caravan industry ‘standard’ that you can load into a van (called payload) is 300kg for a single-axle van and 400kg for a tandem-axle van. However, this is being strongly challenged by many modern caravanners who consider it severely insufficient.

As a consequence, some manufacturers are starting to give vanners a much more generous payload, in some cases up to 600 or 700kg – or even 1000kg in some cases! If you choose to load the van up to its maximum ATM, however, this obviously impacts on your choice of tow vehicle.

And this often causes confusion among vanners. Legally, the vehicle must be rated for the actual loaded weight of the van, not necessarily the stated ATM.

Vehicle Weights

Tow vehicle weights are crucial to know, so you can figure out what van you can tow. All of this information should be in your owner’s manual or freely available online.

Your vehicle will have two weights that represent its maximum towing capacity, given as unbraked and braked. ‘Braked’ means what the vehicle can tow with trailer brakes used; this is the most relevant to caravanners, as trailers can only be ‘unbraked’ if they weigh less than 750kg.

This means the maximum allowed weight of the caravan or camper’s coupling pressing down on the vehicle’s towball.

A rule of thumb ‘generally’ allows for a TBM of 10% of the towing maximum, however not all vehicles follow this rule. You might find, for example, that a vehicle with a 2000kg towing maximum has only a 100kg towball download capacity, limiting your options.

Towbars also have a maximum amount they can bear – and this won’t always be the same as the vehicle’s maximum capacity, especially in the case of it being an after-market accessory. There should be a placard on the towbar stating what the maximum weights are and also in a door jamb of the vehicle.

This is also the case for the towball. While most are rated to 3500kg, not all are. If you have a 2500kg-rated tow ball, and you’re towing more than that, you’ll strike trouble.

Vehicles also have a maximum axle capacity, and the important one to note is the rear axle. Your vehicle, all loaded up with gear in the back and the caravan hitched up, cannot weigh more than the maximum axle mass specified by the manufacturer.

The empty weight of the vehicle in running order – sometimes with 10L of fuel in the tank, and sometimes it’s with a full tank of fuel. However, it doesn’t include any extras like towbars, canopies or nudge bars that may be additions to the vehicle, nor portable items like tool boxes or fridges.

This is the maximum allowable total mass of a fully loaded vehicle, which is the Tare (empty) mass plus the load, including the passengers. It’s specified by the tow vehicle/cab chassis manufacturer.

GCM is specified by the tow vehicle manufacturer and is the maximum combination weight of the towing combination – ie, the maximum laden mass of the tow vehicle and the maximum laden weight of the trailer.

Trailer (Caravan Or Camper) Weights

ATM refers to the maximum legal total loaded mass of a trailer – be it a box trailer, caravan, camper trailer or fifth-wheeler – when it is not coupled to a tow vehicle. It specified by the trailer or chassis manufacturer, is usually stamped on the compliance plate and can not be exceeded.

Specified by the trailer or chassis manufacturer, the GTM is the legal total weight that can be supported by the wheels of a trailer when it is supported by a tow vehicle.

The actual unladen weight of a trailer, with no gear loaded, and all water tanks and gas cylinders empty. Note that this should include all extra fittings like awnings that are attached to the van. However, it often excludes additions made once a van leaves the factory, such as by a dealer.

Otherwise referred to as tow ball weight or just ball weight, this is the weight imposed on the tow vehicle’s tow ball by the RV’s coupling.

Only relevant to fifth wheelers, this is the weight imposed on the hitch on the tow vehicle’s tray. This means that the maximum tow rating and the maximum TBM don’t apply but what does become relevant are maximum payload and maximum axle ratings.

Payload is calculated by subtracting the Tare Mass from the ATM. What’s left is the amount of gear, water and gas you can legally load into a van.

The legal weights for your van will be specified on the compliance plate: