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Caravan Weights: Frequently Asked Questions
What is the difference between tare weight and ATM?
Tare is the caravan's weight as it leaves the factory — empty water tanks, no gas bottles, no luggage. ATM (Aggregate Trailer Mass) is the maximum the loaded caravan is legally allowed to weigh, including everything you pack, full tanks and the downward load it puts on the tow ball. You must keep the actual loaded weight at or under the ATM stamped on the compliance plate.
What is GVM and GCM?
GVM (Gross Vehicle Mass) is the maximum your tow vehicle is allowed to weigh fully loaded — passengers, fuel, cargo, accessories and the tow ball load from the caravan all count. GCM (Gross Combination Mass) is the maximum legal weight of the vehicle and caravan combined, as set by the vehicle manufacturer. You can be under both individual limits and still exceed GCM, so all three numbers need checking.
How much can I legally tow?
Your limit is the lowest of four figures: the vehicle manufacturer's braked towing capacity, the towbar's rated capacity, the caravan's ATM, and what keeps you under GCM once the tow ball load is added to the vehicle's GVM. Exceeding any of them is illegal and can void insurance after an accident.
What is tow ball weight and why does it matter?
Tow ball weight (or ball download) is the downward force the caravan coupling puts on the tow hitch — typically 8–12% of the caravan's loaded weight for stable towing. Too little ball weight causes sway; too much overloads the vehicle's rear axle and lifts the steering. Crucially, ball weight counts toward your vehicle's GVM, and on many utes it eats 1.5x its value from remaining payload once leverage is considered.
Do I need a weight distribution hitch?
A weight distribution hitch (WDH) transfers some of the ball load from the rear axle toward the front axle and the caravan's wheels, restoring steering feel and headlight aim. Many vehicle manufacturers require or recommend one above a certain ball weight — check your owner's manual. A WDH doesn't increase any legal weight limit; it only redistributes load.
Where can I get my rig weighed?
Public weighbridges charge a small fee and give you axle-group figures for the whole combination. Mobile caravan weighing services come to you and produce a detailed report comparing every measurement against your compliance-plate limits — worthwhile after fitting accessories or before a big trip, since most caravanners underestimate their loaded weight by 100–300 kg.
