All the information you need to understand weights so you can travel safe or choose the right tow vehicle. Understand your Caravan Weight and Tow Vehicle Weight.
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In order to tow safely and legally, you must tow within your car's towing capacity, which is the maximum amount of weight your vehicle is able to tow as recommended by the manufacturer. Unfortunately some of the abbreviations, acronyms and definitions regarding weights, can be confusing. And to make matters even more confusing, 3500kg towing capacity as advertised by the manufacturer, does not mean you can tow 3500kg legally.
The information and examples below, will hopefully help you understand weights and what it means for your towing capacity. If you need some help or advice, do not hesitate to contact us with your vehicle details.
Unhitched from Tow Vehicle
ATM is the combined weight of the trailer and its full load when it is not coupled to a tow vehicle.
ATM = Caravan Tare Mass + Max Payload (includes Tow Ball Mass)
Hitched to Tow Vehicle
GTM is the weight of the fully loaded trailer imposed on the trailer’s axle when it is coupled to the tow vehicle. Note, this is when the Caravan or Trailer is carrying its maximum load.
GTM will always be less than ATM as some of the trailer weight is transferred to the tow vehicle when the trailer is hitch to it.
GTM = ATM – TBD
Tare Mass is the weight of the Caravan or Trailer straight off the manufacturer line. This is the total weight of an empty caravan. It does not include people, luggage, water or gas.
Where this gets tricky, is the Tare Mass recorded on your plate, may not be your actual weight. Additional aftermarket accessories are not included in this measurement from the manufacturer, as they are not original components. This includes items like toolboxes, solar panels added and even additional batteries.
Payload is the trailer’s carry capacity. It’s the difference between its Tare Weight (un-laden weight) and its ATM. Payload is important for all trailers, however it is critical to campers and caravans, many of which have quite limited carrying capacity to start with. Modifications and additions to the trailer can very quickly eat into its carrying capacity and result in an overloaded trailer, or the inability to legally carry necessary items.
Max. Payload = ATM – tare mass – TBD
Tare Mass or Tare Weight is the weight of an empty standard vehicle with all of its fluids (oils, coolants) but with only 10 litres of fuel in the tank.
This is the same as Tare Mass, but with a full tank of fuel and without any accessories fitted (bull bars, tow bars, roof racks etc). Think of it as your standard vehicle literally parked at the kerb and ready for you to get in and drive away.
This is the maximum your vehicle can weigh when fully loaded as specified by the manufacturer. GVM is the Kerb Mass plus all accessories (bull bars, roof racks, winches etc) and payload.
Most importantly, if you're towing something, the GVM also includes the Tow Ball Download. (See above)
The GCM is the maximum loaded weight of the towing vehicle and any trailer or caravan being towed while driving on the road.
Payload is the vehicles carry capacity. It’s the difference between its Tare Weight (un-laden weight) and its ATM. Payload is important for all trailers, however it is critical to campers and caravans, many of which have quite limited carrying capacity to start with. Modifications and additions to the trailer can very quickly eat into its carrying capacity and result in an overloaded trailer, or the inability to legally carry necessary items.
Here is a break down of the towing weights for a Ford Everest using the terminology above. For this example the following manufacture specifications and Caravan Weights will be used:
Vehicle: 2021 Ford Everest Trend 4WD 3.2L
Max Towing Capacity: 3000Kg - the maximum amount of weight your vehicle can tow when pulling a trailer as determined by Ford
Caravan Weight: 3100 Kg Aggregate Trailer Mass (ATM) . This is the maximum weight of the Caravan when carrying the maximum load recommended by the manufacturer.
Ford Everest Trend 4WD 3.2L fully loaded to Max GVM
|Gross Combination Mass: This is the maximum combination weight of the vehicle and caravan. In the example, when the caravan is hitched to the vehicle, the total weight can not legally exceed 5800Kg.
|Gross Vehicle Mass: This is the maximum legal weight of the car fully loaded (Passengers, Accessories, Fuel etc). When the vehicle is hooked up to the van, the tow ball weight is calculated as part of the vehicles weight. We will add this below to make it clearer.
|The Kerb Weight is the empty car with a full tank of fuel. No accessories. (As defined by Ford). Each car fanufacture can be different here. Some only include 10L of fuel. In this case, Ford include a full tank.
|This is how much you can carry in/on the car. This includes passengers, accessories like bull bars, roof racks etc and luggage. It is calculated by deducting the Kerb Weight from the GVM. i.e. = GVM - Kerb Weight.
|Deduct Tow Ball Weight
|The Tow Ball Weight adds the weight to the vehicle when hitched. This deducts from your available payload in the car as it contributes towards your GVM. In this example, we assume 8% of fully loaded Caravan with an ATM of 3100 kg (8%-15% is average).
|Payload remaining for passengers, luggage and accessories before reaching the maximum GVM of 3100Kg
|So now assume you add 4 people and luggage to the car weighing 415kg. This means the car is now fully loaded to its maximum legal weight of 3100Kg (GVM)
|Reduced Towing Capacity
|Now we have to consider the Gross Combination Mass of 5800Kg. This can not be exceeded. So, when the car is fully loaded to 3100kg, there is only 2700Kg left before exceeding the Max Combination Mass of 5800 Kg. This means if your Van of 3100Kg is loaded to more than 2700 Kg, you would be overweight and towing illegally. Not to mention uninsured