Article from Caravan and Camping Australia
Anyone who’s toughed it out ‘til stumps at any happy hour around this country will testify, the one topic which invariably comes up is weight. And they’re not talking about the size of your co-pilot, partner or your rather rotund, portly neighbour; they’re talking about Tare, GVM, GCM and payload.
For some reason, when it comes to getting our head around these rather important figures, some of us struggle. A quick perusal of any caravan or camping Facebook group will confirm the confusion. What begins as a seemingly simple query by some unsuspecting newbie member foolish enough to pose the question soon escalates into a full blown debate about whose tug can handle what weight and tow which caravan while carrying whatever accessories while arguing whether the TBM is to be subtracted from the GVM or the ATM, are accessories included in the caravan TARE…. #%*@+* …On it goes, ad nauseam.
Meanwhile, the unsuspecting newbie, reeling from the violent debate still raging, has left the group and is most likely in search of some form of counselling while considering whether to sell the tug and the caravan and buy a motorbike and a 2 man tent.
So why the confusion?
I think it stems, in part, from the misinformation provided by some caravan manufacturers and/or car sales folk. For example, almost anyone who has bought or looked at buying a Ford Ranger/Mazda BT50/Holden Colorado will have been told they have a braked towing capacity of 3500kg, and while this is true, what they don’t tell you is the vehicle has to be almost empty for this to happen, such are the constraints of the pesky and oft maligned GCM.
Likewise, your caravan manufacturer might write your caravans TARE on the contract of sale but neglect to mention the you-beaut accessories he has just sold you, such as the extra gas bottle, solar system, roof mounted television satellite etc. will not be included in the TARE weight, but will in fact be eroding your payload.
So let’s look at the terminology used and how it applies to your set-up.
Tare Mass: We will start with this one because it seems to be the one which creates the most confusion. Tare should be the weight of your caravan as it leaves the manufacturer. This doesn’t include gas in the gas bottles, water in the tanks or, in most cases, any extra accessories you’ve had factory fitted, such as the ones mentioned above. Some manufactures, and I stress some, will include accessories such as air conditioners and awnings etc. in the TARE but this is the exception to the rule not the norm. ALWAYS make sure you know how the accessories will be treated in relation to your TARE and make doubly sure it’s written on your contract before you sign it.
Likewise, your vehicle TARE will not include passengers, fuel or accessories. In the case of the Ranger for example, a payload of 900kgs is soon eaten away when you start fitting bull bars, winches, canopies passengers, fuel etc.
GVM/GTM Gross Vehicle Mass/Gross Trailer Mass: Is the combined Tare and Payload, the maximum weight which can be imposed on the axle or axles when the caravan is fully loaded and connected to the tow tug. It’s the same for your vehicle but remember, your vehicle GVM also includes tow ball mass (TBM) when the car is connected to your caravan.
ATM Aggregated Trailer Mass: Is the maximum your caravan is allowed to weigh when DISCONECTED from your tow tug. This should be equal to your Tare Mass plus your maximum payload.
Payload: This is anything you add to your caravan or vehicle tare except occupants of the caravan when the caravan is stationary. In the case of your caravan this will include things like gas, water, clothing, food, cutlery, crockery, toiletries etc. Where your factories accessories such as solar systems, batteries or awnings are not included in your tare, they must be included in your payload.
Your vehicle payload will include aforementioned accessories such as bull bars, canopies etc. it will also include any occupants.
TBM Tow Ball Mass: This is the weight that is applied to the tow ball when you connect your caravan to your tug. As mentioned above, this figure is included in your vehicles Payload. As a rule of thumb the tow ball mass of a caravan in Australia is roughly around 10% of the caravans ATM. To me, this is a much underappreciated figure. Too little TBM can affect the towing dynamics of the caravan resulting in sway. Likewise, too much TBM can have detrimental effects on the tugs steering and braking stability and also limit your control of the vehicle. Most vehicle handbooks will specify a maximum TBM and it is sometimes marked somewhere on the vehicles towbar.
GCM Gross Combined Mass: This is the maximum weight of your caravan, tug and the payload in both. As a rule you will never have to worry about GCM if, and it’s a big IF, you’re within the limits of the previously mentioned GVM/ATM/Payload.
There are other factors which may impact the actual number written on your vehicle or caravan compliance plate which can bring an unsuspecting nomad to grief. For instance, some vehicle manufacturers stipulate a reduced speed when towing above a certain weight.
Bottom line is do your research, ask loads of questions before opening your wallet, make sure your contract is clear and defined before signing off and most importantly, know where your local public weigh bridge is located. Because at the end of the day, regardless of what the used car salesman or caravan manufacturer told you, you’re responsible for your weights when you hit the road.