Understanding ATM and Tare Weight on your Caravan

Two figures on your caravan compliance plate are critical for safe and legal towing in Australia: Tare Mass and ATM. Understanding these numbers helps you match your hybrid caravan correctly to your tow vehicle, pack within limits, and remain compliant on Australian roads.

Arctic Glacier Hybrid Caravan

Key definitions


Tare (Tare Mass)

Tare is the mass of the caravan as manufactured, including all standard equipment fitted at the time of manufacture. It does not include personal belongings, water in tanks, food, clothing, or aftermarket accessories added after delivery.

  • Water is not included in tare.
  • Gas bottles may be included only if declared as standard equipment by the manufacturer and listed accordingly. Always refer to your compliance plate and owner documentation.


ATM (Aggregate Trailer Mass)

Aggregate Trailer Mass is the maximum allowable total mass of the caravan when standing on its own wheels and jockey wheel and not connected to the tow vehicle.

ATM includes the caravan’s tare mass plus all load carried for travel. This includes water, gas, personal gear, accessories, and any aftermarket additions.

Important: ATM includes the portion of weight that will transfer to the tow ball when the caravan is hitched. The caravan’s total mass does not change simply because some weight shifts to the vehicle.


Why these numbers matter

Operating above rated capacities can result in:

  • Increased braking distances
  • educed stability at highway speeds
  • Increased stress on suspension, tyres, chassis, and coupling
  • Potential legal, insurance, and compliance consequences


Payload

Payload is the amount you can add to the caravan. Payload = ATM minus Tare

Example

If your caravan has a tare of 2,200 kg and an ATM of 2,800 kg, your payload capacity is 600 kg.

Keep in mind:

  • 1 litre of water weighs approximately 1 kg
  • Aftermarket accessories reduce available payload
  • Lithium batteries, additional solar, toolboxes, generators, and extra spare wheels all count toward total mass
Arctic Glacier 16 HR Hybrid Caravan

Other Important Weight Terms

GTM

Gross Trailer Mass is the maximum mass permitted on the caravan’s wheels and axles when the caravan is hitched to the tow vehicle. It excludes the tow ball mass.

When hitched and correctly loaded: ATM equals GTM plus tow ball mass


Tow Ball Mass

This is the downward force applied to the tow vehicle’s tow ball when the caravan is connected.

A common guideline is approximately 8 to 15 percent of ATM, however the correct value must not exceed the lowest rated limit of:

  • The tow vehicle
  • The tow bar
  • The coupling

Incorrect loading distribution can significantly affect tow ball mass and vehicle handling.


Vehicle Ratings

GVM

Gross Vehicle Mass is the maximum allowable mass of the vehicle when loaded, including passengers, fuel, cargo, and tow ball mass.

GCM

Gross Combination Mass is the maximum allowable combined mass of the loaded vehicle and loaded caravan. Your legal operating limit is determined by the lowest applicable rating across:

  • Caravan ATM and GTM
  • Vehicle towing capacity
  • Vehicle GVM
  • Vehicle GCM
  • Tow bar rating
  • Tyre load ratings
Arctic Frost 13 Hybrid Caravan

Where to Find Your Caravan’s Weights

Your caravan compliance plate lists Tare, ATM, GTM, and tyre specifications.

For Arctic Campers, the compliance plate is typically located on the drawbar. Location may vary between manufacturers.

Important: The compliance plate reflects the caravan as manufactured. If you have added accessories or made modifications, your real world weight may differ.

How to Check Your Weights

The only way to confirm compliance is to weigh your setup.

Recommended method:

  • Load the caravan and vehicle as you would for travel.
  • Weigh the full combination.
  • Weigh the vehicle alone.
  • Calculate the caravan mass.


Alternatively, use a professional weighing service for the most accurate interpretation, particularly after modifications or before extended remote travel.

Common Mistakes to Avoid

  • Assuming tare equals real travel weight
  • Ignoring GVM or GCM while focusing only on towing capacity
  • Forgetting that aftermarket accessories count toward mass
  • Incorrect loading that alters ball weight and stability
  • Failing to re weigh after upgrades

FAQ

What is ATM in simple terms

ATM is the maximum total weight your caravan is legally allowed to weigh when fully loaded and unhitched.

No. Water is not included in tare.

Yes. ATM includes all load carried for travel, including water and gas.

ATM is the total allowable mass of the caravan unhitched. GTM is the allowable mass on the caravan wheels when hitched, excluding tow ball mass.