Understanding Your Caravan Weights — Why ATM, GTM & GVM Matter
Understanding ATM, GTM, and GVM is essential for safety, legality, and optimal towing. You need to understand your caravan or trailer’s weight specifications, so that you can choose the right hitch for your towing needs.
ATM (Aggregate Trailer Mass) refers to the maximum permissible weight of your caravan when fully loaded and ready to tow. It includes everything: gear, water, luggage, and accessories. Your Caravan/RV’s ATM is set by the manufacturer, and can be found on your van’s compliance plate. Your coupling must be rated to tow your ATM even if the van is not loaded to the maximum allowed by the ATM. Above 3.5 tonne in Australia the suitability of the coupling is defined by its certified D-value and V-value. The formula for calculating the required D-value and V-value is available on request. Hitch-Ezy’s 5 tonne version has a D-Value of 30.2kN and a V-Value of 16.1kN
GTM (Gross Trailer Mass) refers to the weight on the caravan’s axles when the caravan is fully loaded. This number will be lower than the ATM because some weight is born by the tow vehicle when the coupling presses down onto the tow-ball or tow-pillar.
GVM (Gross Vehicle Mass) is the maximum allowable weight of your tow vehicle when fully loaded. The load includes occupants, fuel, cargo, and the weight pressing down on the tow-bar from any caravan or trailer you are towing. It’s determined by the vehicle manufacturer, and is usually found on a compliance plate or in the owner's manual. Towing a loaded caravan pushes your vehicle’s chassis, brakes, suspension, and drive train.
Why does all this matter? Because you want to arrive at your destination safely. Overloading is not just illegal and may invalidate your insurance; it is DANGEROUS. Overloading impairs braking and handling. It reduces towing vehicle and van stability, which may culminate in uncontrollable sway and van rollover.
Hitch-Ezy’s unlimited articulation means that a caravan rollover does not force the towing vehicle to rollover. In the event of a trailer rollover, having an unlimited articulation hitch may even save your life. Because Hitch-Ezy tows on a unique pillar there is also no slop between the trailer and the towing vehicle. Consequently there is none of the clunking commonly associated ball type couplings and pintle hooks; just smooth silent towing. Hitch-Ezy’s patented design ensures smooth uncoupling is always possible regardless of any angle between the tow-vehicles and the trailer being on sloped terrain or the presence of a residual load between towing-vehicle and trailer when you come to a halt. Hitch-Ezy’s automatic double locking also minimises the chances of failing to make a secure connection.
So whether you’re bashing along Aussie outback tracks or cruising US highways it’s important to use a coupling suited to your needs, and rated to your rigs ATM, GTM, and GVM.