GVM, ATM, TBM? Caravan Weights Explained
If you’re thinking about getting into caravaning but haven’t bought a van or a tow vehicle yet, you’re in the perfect position to get things right from the start. Before you fall in love with a caravan at the dealership or grab that dual cab ute on sale, you need to understand one thing: weights.
Acronyms like GVM, ATM, TBM, and GCM aren’t just red tape, they’re make-or-break numbers that will decide what you can tow, how safely you can do it, and whether your setup is even legal.
In this guide, we’ll break down each of the key towing terms, show you how they fit together, and help you avoid the common traps that leave new caravan owners stuck, overloaded, or frustrated.
What All the Caravan and Towing Acronyms Really Mean
Before you buy a caravan or a tow vehicle, get yourself familiar with these key weight terms. They form the rules of the game when it comes to safe and legal towing.
Let’s start with the “empty weights,” but keep in mind—no one tows empty. The loaded figures are what actually matter on the road.
Kerb Weight (Car, Ute, SUV)
- The weight of the tow vehicle with a full tank of fuel, all standard fluids, and no passengers or cargo and no accessories, not even a tow-bar.
- Why it matters: It’s your starting point to work out how much payload (stuff) you can carry.
Tare Mass (Caravan)
- The weight of the caravan or tow vehicle when it leaves the factory. Includes standard equipment but no water, gas, luggage, food, or people.
- Why it matters: Tells you how much capacity you have before hitting your legal limits.
Reality check: Kerb weight and Tare are rarely what you’re driving or towing with. You’ll always be over those numbers. In theory, they’re useful. In reality? They’re mostly academic.
GVM – Gross Vehicle Mass
- The maximum legal weight of your tow vehicle, fully loaded with driver, passengers, fuel, gear, and if towing the tow ball weight (TBM)
- Set by the manufacturer. You can get this upgraded, but bear in mind there are a lot of caveats, like it may not include GCM or rear Axle loads upgrades, then there is pre / post rego, and each state has different rules.
- Why it matters: Many people exceed GVM without realizing it, especially when towing.
ATM – Aggregate Trailer Mass
- The maximum loaded weight of the caravan when it’s not hitched up.
- Includes everything: water, gas, food, clothes, bikes, annexes.
- Why it matters: This is the top limit stamped on your caravan compliance plate. Exceed it and you’re illegal. This is where the caravan payload comes in. Too small and you will blow it easily.
TBM – Tow Ball Mass
- The downward force the caravan applies to the vehicle’s tow ball.
- Usually 8–12% of the ATM, but it depends on loading and caravan design.
- Why it matters: It counts toward your car’s GVM and rear axle load. Too heavy, and you could be overloaded even if your van is “legal.”
GTM – Gross Trailer Mass
- The caravan’s total weight when hooked up, meaning part of the weight is on the car via the tow ball.
- GTM = ATM – TBM
- Why it matters: GTM sits on the trailer’s own wheels, so it’s what your caravan axles and suspension are handling.

GCM – Gross Combination Mass
- The maximum total weight of the tow vehicle and the caravan combined.
- Set by the tow vehicle’s manufacturer.
- Why it matters: Even if both your car and van are under their own limits, you can still be over GCM. That’s a common mistake.
Rear Axle Load
- Even if you’re under GVM and GCM, you can still be overloaded if your rear axle is carrying too much.
- Tow Ball Mass (TBM) transfers directly to the rear axle.
- Add a canopy, drawers, fridge, tools, and passengers, all of that piles onto the rear.
- Most utes and wagons have lower rear axle limits than you’d expect.
Payload
- How much weight you can add to the car or caravan before hitting the GVM or ATM.
- Payload: Car=GVM – Kerb (Caravan= ATM – Tare)
- Why it matters: Accessories, tools, people, food, water, camping gear—all this eats into your payload.
Where to Find Towing Specs for a Vehicle
Sometimes it is not easy to find on the manufactures website. You can try the handbook for your car or my favorite way is a search through Google on Redbook.com.au, I would do a search like below –
Google search i.e redbook Isuzu D-max 2023, or use the search on redbook.com.au

Find the particular model of car that you have, then scroll down and go to Overview –> Specifications –> Dimensions & Weights
Below are the main specifications we are concerned about for this example vehicle.
- Tare Mass 1960 kg
- Kerb Weight 2015 kg
- Gross Vehicle Mass (GVM) 3000 kg
- Gross Combination Mass (GCM)5850 kg
- Payload 985 kg
- Towing Capacity (braked) 3500 kg
- Maximum Towball Download (TBM) 350 kg
- Maximum Front Axle Load 1450 kg
- Maximum Rear Axle Load 1910 kg
For the caravan you should be able to get the ATM from the manufactures site, or the compliance plate.
Summary
Whether you’re towing a small pop-top or a full-size off-road caravan, your tow vehicle needs to match the weight, the purpose, and the legal limits. Here’s a breakdown of the main classes of tow vehicles in Australia with one or two examples for each.
Also you need to consider how long your road trips are going to be, a few weeks/year, then you probably want an all rounder vehicle, longer time frame say a year + then probably might want to move up a size or two.
For maximum stability when towing, you want the tow vehicle to be heavier than the towed vehicle.
1. Dual Cab Utes (Most Common for Touring)
Great balance of towing capacity, payload, and versatility. Perfect for towing most caravans under 3,000 kg.
- Isuzu D-MAX — 3,500 kg towing, 6,000 kg GCM, known for reliability and simplicity.
- Ford Ranger — 3,500 kg towing, strong GCM and tech, great all-rounder.
2. Large 4WD Wagons (Comfort + Capability)
More comfortable for long-distance touring with the family. Often slightly lower payload than utes, but better ride quality.
- Toyota LandCruiser 300 Series — 3,500 kg towing, strong GCM, built for towing big vans.
- Nissan Patrol Y62 — 3,500 kg towing, reliable, great option under $90k, same as the Landcruiser, built for towing and off-road conditions.
3. American Pickups (Heavy Towing Power)
Ideal for big caravans, toy haulers, or towing with high payload. Expensive, but very capable.
NOTE: If your GVM goes over 4,500 Kg, you will need to get a LR truck license.
- RAM 2500 — up to 12,000kg GCM, with correct setup
- Chevrolet Silverado 2500 — Heavy-duty towing, over 12,000 kg GCM, engineered for serious loads.
4. Light Trucks (For Big Vans or Conversions)
For those towing extremely heavy rigs or converting to motorhome/truck + fifth-wheeler setups. Higher GVM and GCM than most utes or 4WDs.
- Isuzu NLR 45-150 — 4,500 kg GVM, 8,000 kg GCM, car licence legal.
- Hino 300 717 — 6,500+ kg GVM, great base for truck camper builds or heavy towing.