Weights buying guide · 7 min read
Caravan weights: work through the numbers before you shortlist
A plain-English example of tare, ATM and the load left for options, water and gear, with the checks to make on the actual caravan.
Start with the rating and the exact build
Aggregate trailer mass (ATM) is the manufacturer’s maximum loaded mass for the trailer, including the load imposed through the coupling. Tare is the unladen reference mass. On paper, ATM minus tare gives the maximum load that can be added to that reference build. The plate and figures for the caravan being supplied matter more than an indicative range page.
A published tare may describe a standard layout before selected equipment is fitted. A change in batteries, tanks, spare wheels or other options can change the actual empty mass and reduce room for what you pack. Ask what the manufacturer’s stated tare includes and obtain the individual unit’s plate and written weight information.
- Record the exact model year, floorplan and options beside each mass figure.
- Ask for the supplied unit’s plate and a written explanation of its tare, ATM and GTM.
- Do not treat an indicative tare as an independently measured mass.
Source: Australian Government VSB1 Revision 6: ATM, GTM and tare
A worked example, not a tow-vehicle check
Imagine a caravan with a published tare of 2,200 kg and ATM of 3,000 kg. Subtraction gives 800 kg of nominal load allowance for that published reference build. Suppose separately added equipment accounts for 100 kg, the water you plan to carry for 160 kg, and food, clothing and other gear for 120 kg. Those assumptions total 380 kg; 800 minus 380 leaves 420 kg on paper.
The arithmetic is useful for spotting questions, not for certifying a loaded caravan. The assumed equipment might already be in the stated tare, or the ordered van might weigh more than the reference. Ask what is included, then have the actual loaded caravan weighed through an appropriate service. ATM alone does not establish whether any particular tow vehicle and combination are compliant or suitable.
- Show every addition and its assumed mass in a written list.
- Check whether water, gas, batteries, accessories and dealer-fitted items are already in the tare figure.
- Keep a margin for items you have not yet counted.
Compare the same kind of figure across vans
A 2,200 kg estimated tare for one standard layout and a measured unit-specific tare for another are different kinds of evidence. Put the source, date, configuration and any “approximate” wording beside each number. If one model has no ATM, keep it unconfirmed in a filter rather than estimating it from another model.
GTM and tow-ball load are separate figures. The federal trailer guidance explains how ATM and GTM relate to the mass carried at the coupling. Obtain the actual ratings and seek a qualified assessment of the full towing combination when making a vehicle decision.
Source: Australian Government VSB1 Revision 6: ATM, GTM and tare
Questions to take to the dealer
Ask for the final model code, option list and individual unit identification, then request the plate figures and an itemised quote together. This connects the mass data to the build you would actually receive. If a brochure and current page disagree, ask the dealer to identify the controlling revision in writing.
- Which mass values are for this exact build and which are estimates?
- What changes if the ordered options or compliance-plate tare differ?
- Where can I have the loaded unit weighed after handover?
- What do the applicable vehicle, towbar, hitch and combination ratings require?