Measuring the distance between the
wheel arches and the ground – seen
here at an Everything Caravan and
Camping safety inspection – when
hitched and unhitched is the ideal
way to assess whether a WDH is
necessary.
PAYLOAD
To determine the maximum amount of weight
you can store in your trailer, subtract the Tare
mass from the ATM. As an example, if the ATM is
3500kg and the Tare weight is 2800kg, the total
payload for that van is 700kg.
The difficulty starts when determining how to
load your trailer in such a way that you do not
exceed either the GTM or the maximum towball
mass. Fortunately, most modern caravans
manufactured by the better known brands
are computer designed, so that when the van
is packed properly, the weight of the load is
distributed appropriately. To be certain that you
have packed your trailer properly, the only way to
check it is to put the van on a weighbridge.
As a general rule, 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.
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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 both 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.
Always seek advice from an expert when fitting
and adjusting a WDH.
Next month, we will look at what happens
when you couple the trailer to the tow vehicle,
particularly the effect of transferring the towball
mass to the towing vehicle.
GETTING HELP
Understanding this weight issue and applying it
to your specific situation is difficult to say the
least. Nowadays, there is a concerted effort to
give RVers access to expert advice on assessing
their rig and understanding what they need to do
to be legal and safe.
Caravanning Queensland has been offering free
caravan safety-check events around the state
for a number of years. It publishes a schedule of
events and locations for each year on its website.