Caravan and tow vehicle weights explained for NZ roads.

How caravan and tow vehicle weights work

Towing a caravan should feel relaxing, not stressful. But to tow safely and legally, it’s important to understand what your vehicle and caravan can actually handle.

If your setup is overweight or poorly loaded, you risk insurance not covering you, breaking the law, or dealing with dangerous sway when braking or swerving. It can also put unnecessary strain on your engine, tow bar, suspension, and running gear, and in some cases lead to fines or being taken off the road.

The good news?

Once you know your numbers, it all becomes much simpler. Sorting your weights early gives you confidence on the road and helps you enjoy the trip, knowing your setup is safe and compliant.

Where to find your caravan weights

Every caravan has a compliance plate fitted by the manufacturer. This shows the key weights you need to know, including tare weight, tow ball weight, aggregate trailer mass (ATM), and gross trailer mass (GTM).

You’ll usually find it in the front boot or tunnel boot. If you’re not sure where to look or what the numbers mean, just give us a call, we’re always happy to help.

Where to find your tow vehicle specs

Your tow vehicle’s towing limits are set by the manufacturer and depend on the exact make, model, and variant. These include towing capacity, kerb weight, tare weight, maximum tow ball mass, gross vehicle mass (GVM), and gross combination mass (GCM).

You can find this information on a plate inside the door frame, in the owner’s manual, or online. Just make sure you’re looking at the correct vehicle details.

Keep in mind that accessories like bull bars, roof racks, tow bars, and extra spares all add weight, even if they’re not included in the factory figures.

Mobile weighing, wherever you are

Weigh Safe is a mobile weighing service, so we come to you. We’re based in Timaru and regularly service Christchurch, with trips throughout the wider South Island. Whether you’re at home, in storage, or getting ready for a trip, we bring certified scales to your location and give you clear, accurate weights.

Got questions about your setup? Get in touch and we’ll talk it through.

Key tow vehicle weights

Towing capacity – The maximum your vehicle can legally tow. Your caravan’s ATM must be under this.
Braked towing capacity – The legal limit when towing a braked caravan, assuming a working brake controller is fitted.
Kerb weight – Vehicle weight with fluids and a full tank of fuel, no people or gear.
Tare weight (vehicle) – Similar to kerb weight, but with only 10 litres of fuel.
Maximum tow ball weight – The downward load on the tow ball. Both the vehicle and tow bar have limits.
GVM (Gross Vehicle Mass) – The maximum your vehicle can weigh fully loaded, including people, gear, fuel, and ball weight.
GCM (Gross Combination Mass) – The maximum combined weight of the vehicle and caravan, fully loaded.
Payload – How much you can load into the vehicle.
GVM minus kerb weight = payload.
Tow bar rating – Your tow bar has its own limit. The lowest-rated component always wins.

Caravan weights made simple

Tare weight – Empty caravan as built, with factory options only. Water and gas empty.
Tow ball mass (TBM) – The weight the caravan puts on the tow ball. This changes depending on loading, water, gas, and gear. Best checked with a scale.
ATM (Aggregate Trailer Mass) – The maximum the caravan can weigh when fully loaded and unhitched.
GTM (Gross Trailer Mass) – The weight carried by the caravan axles when hitched.
ATM minus tow ball weight = GTM.
Caravan payload – How much you can load into the caravan.
ATM minus tare weight = payload. Everything you add eats into this.

See what's covered in the Weighing Report.