To understand what size of caravan you can tow with your tow vehicle it is important to understand the meanings of the terminology used.
The following terms are the most common used when discussing towing possibilities and weight ratings related to small trailers. These are the official ADR definitions:
AGGREGATE TRAILER MASS (ATM) – the total mass of the laden trailer when carrying the maximum load recommended by the ‘Manufacturer’. This will include any mass imposed onto the drawing vehicle when the ‘Combination Vehicle’ is resting on a horizontal supporting plane.
GROSS COMBINATION MASS – value specified for the vehicle by the ‘Manufacturer’ as being the maximum of the sum of the ‘Gross Vehicle Mass’ of the drawing vehicle plus the sum of the ‘Axle Loads’ of any vehicle capable of
being drawn as a trailer.
GROSS TRAILER MASS (GTM) – the mass transmitted to the ground by the ‘Axle’ or ‘Axles’ of the trailer when coupled to a drawing vehicle and carrying its maximum load approximately uniformly distributed over the load bearing area, and at which
compliance with the appropriate Australian Design Rules has been or can be established.
GROSS VEHICLE MASS (GVM) – the maximum laden mass of a motor vehicle as specified by the ‘Manufacturer’.
LIGHT TRAILER (TB)
A trailer with a ‘Gross Trailer Mass‘ not exceeding 3.5 tonnes, other than a trailer of Category TA.
MEDIUM TRAILER (TC)
A trailer with a ‘Gross Trailer Mass‘ exceeding 3.5 tonnes but not exceeding 10 tonnes.
RATED TOWING CAPACITY – the lesser of either;
– the rating given to the towing equipment fitted to the motor vehicle or,
– the difference between ‘Gross Combination Mass’ and ‘Gross Vehicle Mass’.
TARE MASS – mass of a vehicle other than a L-group vehicle ready for service, unoccupied and unladen, with all fluid reservoirs filled to nominal capacity except for fuel, which shall be 10 litres only, and with all standard equipment and any options fitted.