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    Sunrise Caravans
    Education First

    Caravan Weights Explained

    Tare, ATM, GTM, ball weight, payload, GVM and GCM, in plain English. Ten minutes here could save you a world of pain at the weighbridge.

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    The Seven Numbers That Matter

    Every one of these is stamped on a plate somewhere on your van or car. Here is what each one actually means.

    Tare

    What the van weighs empty, straight off the line. No water, no gear, no gas bottles.

    This is the number builders quote because it looks lightest. It is also the most misleading.

    ATM

    Aggregate Trailer Mass. The most the van is allowed to weigh, fully loaded and not hooked to the car.

    This is the number that decides whether your car can legally tow the van. Always match your car to the ATM, never the tare.

    GTM

    Gross Trailer Mass. The most the van can weigh on its own wheels while it is coupled to the car.

    It is basically the ATM minus the bit sitting on the tow ball. You will see GTM stamped on the compliance plate.

    Tow ball weight

    The part of the van's weight that pushes down on your car's tow ball. Usually about 10 percent of the ATM.

    People forget this one. It counts against your car's payload, so it is not free capacity.

    Payload

    The difference between the ATM and the tare. This is everything you add: water, gas, batteries, clothes, tools and the dog.

    A van can lose 300 to 400kg of payload to water and gear before you have packed a single swag.

    GVM

    Gross Vehicle Mass. The most your car is allowed to weigh, fully loaded, including that tow ball weight.

    Add passengers, cargo and the ball weight. If that beats the GVM, you are over legal, even with a smaller van.

    GCM

    Gross Combination Mass. The most your car plus a fully loaded van is allowed to weigh, all up.

    This is the big one people miss. The car and van can each be legal while the combination is not.

    A Worked Example, With Round Numbers

    Say a couple buys a van and a car to match. Here is how the sums stack up. These are example figures, so run your own numbers with your own plates.

    • Van tare 1,850kg, van ATM 2,200kg. Ball weight about 220kg.
    • Car rated to tow 3,500kg. The van's 2,200kg ATM fits with room to spare.
    • Car GVM 3,100kg. Weighbridge weight with passengers and cargo sits at 2,500kg, leaving 600kg of payload.
    • Ball weight 220kg, plus a fridge and gear at 180kg, plus the couple at 150kg. That is 550kg, under the 600kg limit.
    • Car GCM 6,000kg. Loaded car 3,100kg plus loaded van 2,200kg is 5,300kg. Legal, and 700kg of breathing room.

    Notice the van only stayed legal because the car had enough payload. The same van behind a car with less payload can be over on the ball weight before you leave the driveway.

    The Four Mistakes That Catch People Out

    We see these every week, from first time buyers through to people doing their third lap.

    Matching the tare instead of the ATM

    A van quoted at 1,850kg tare can easily weigh 2,200kg loaded with water, gas and gear. Match your car to the ATM and you will never be caught out.

    Forgetting the ball weight

    Ball weight eats into your car's payload, along with passengers, a fridge and all the camping gear. Work it in from the start, not at the weighbridge.

    Ignoring the GCM

    Check the combined weight of the loaded car and the loaded van against your car's GCM. It is stamped on the plate, and it is the one number that catches full time tourers.

    Guessing instead of weighing

    Estimates about gear always come in light. A public weighbridge costs about 20 dollars and tells you the truth before you tow anywhere.

    Check Before You Tow

    1. Find the van's ATM on its compliance plate.
    2. Find your car's braked towing capacity, GVM and GCM on its plate or in the owner's manual.
    3. Make sure the ATM is under the towing capacity, with room to spare.
    4. Add ball weight, passengers and cargo, and check the total stays under the car's GVM.
    5. Add the loaded van to the loaded car and check the total stays under the GCM.
    6. If any number is close, weigh the rig at a public weighbridge before your first big trip.

    Want a second opinion on a van you already own or one you are looking at? Send us the details and we will tell you straight.

    Weights FAQs

    What is the difference between ATM and tare?
    Tare is what the van weighs empty. ATM is the most it can legally weigh loaded. When you are matching a van to your car, always use the ATM. Every van comes with its weighbridge docket, so you know its real weight, not a brochure guess. Use a public weighbridge for your loaded combination.
    What is GTM?
    GTM is the most the van can weigh on its own wheels while coupled to the car. It is roughly the ATM minus the tow ball weight, and it is stamped on the compliance plate.
    What is tow ball weight and why does it matter?
    It is the share of the van's weight pressing down on your car's tow ball, usually about 10 percent of the ATM. It counts against your car's payload, so it needs to be part of your sums.
    Does my licence cover a big caravan?
    In Queensland a normal car licence covers towing a caravan when your car's own GVM is 4,500kg or less. Heavier tow vehicles need a heavier licence class, so check with TMR if you drive a truck or a converted ute.
    How do I check my rig is legal before a long trip?
    Write down the ATM, your car's towing capacity, GVM and GCM, and run the sums in our towing guide. If you are not sure, send us your car details and we will check the match for you.

    Ready to put the theory to work? Use our towing guide and weight calculator to match your car to a van.

    Know Your Numbers? Now Find the Right Van

    Tell us what you tow with and we will match you to a van that fits, with the weights written down so you can check them yourself. No BS. No pressure.

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