As a general rule , when the van is loaded for a trip , you should aim to have a towball mass of about eight to 10 per cent of the total weight of the trailer . The ratings on the compliance plate should reflect that . As an example , a caravan with an ATM of 3500kg will normally have a maximum

towball mass of 350kg . If its less than seven per cent , there ' s a good chance you are reading the figure for the unladen towball mass . Some European caravans , however , have particularly low maximum towball mass ratings .

Another potential issue to be aware of is the effects of a weight distribution hitch ( WDH ). As the name suggests , a WDH redistributes the towball weight of the trailer from the rear of the tow vehicle to the front wheels of the tow vehicle as well as the trailer axles . In other words , you could exceed the trailer ’ s GTM using a WDH . If you have any doubt when fitting your WDH , especially for the first time , seek advice from an expert .

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KERB MASS

The Kerb Mass or Unladen Mass of a vehicle , according to the Australian Design Rules ( ADRs ), is the mass of the vehicle in running order , unoccupied and unladen , with all fluid reservoirs filled to nominal capacity , including fuel , and with all standard equipment . It is generally not stated on a vehicle compliance plate .

Obtaining the Kerb Mass of your particular tow vehicle can be a difficult process . If you obtain it from the vehicle manufacturer ' s website in Australia , it should comply with the requirements of the ADRs . If it comes from an overseas website , it may or may not include fuel .