There are now around 938,000 caravans and campervans registered in Australia. That figure comes from Tourism Research Australia's 2025 data, and it's up roughly 32% on 2019, an all-time record. More vans on the road than ever. More gear packed into them than ever. And here's the uncomfortable part: surveys and roadside weigh-ins keep finding that a large share of them are towing overweight, usually without the owner having any idea.
Towing weights are where a lot of good trips quietly go wrong. Not because people are reckless, but because the numbers are genuinely confusing. GVM, GCM, ATM, GTM, tare, kerb, payload, tow ball mass. Nine terms, several of which sound almost identical, all interacting in ways that aren't obvious until someone lays them out properly.
That's what this guide is for. Plain English, Australian conditions, every towing weight that actually matters. We'll cover the maths that connects them, the law (which catches out even careful people), how to weigh your rig properly, and the part almost nobody mentions: what all that weight does to your tyres and wheel bearings.
You don't need to be an engineer to follow this. By the end you'll be able to read your compliance plate, work out whether your setup is legal, and know exactly what to check before the next big trip.
One thing to get straight early. Being "legal" on paper and being "under every limit and safe" are not the same thing. The gap between those two is where most people come unstuck, and we'll keep coming back to it.
Every towing weight acronym, in one table
Before we dig into each one, here's the whole vocabulary in a single place. Your tow vehicle has its own set of weights. Your caravan or trailer has its own set. And then there's one number that governs the two of them together. Get those three groups straight and the rest falls into place.
| Term | Stands for | What it means in one line | Where to find it |
|---|---|---|---|
| Tare Mass | (tare) | The empty weight of the vehicle or trailer, with about 10 litres of fuel and nothing loaded | Compliance/trailer plate, owner's manual |
| Kerb Mass | (kerb) | Like tare, but with a full fuel tank and usually all standard fluids | Manufacturer specifications |
| GVM | Gross Vehicle Mass | The most your loaded tow vehicle is allowed to weigh | Vehicle compliance plate (door jamb) |
| Payload | (payload) | What's left over for people, fuel, gear and tow ball weight (GVM minus kerb) | You calculate it |
| GCM | Gross Combination Mass | The most your loaded car and loaded trailer are allowed to weigh together | Vehicle compliance plate / manufacturer |
| ATM | Aggregate Trailer Mass | The most your loaded caravan is allowed to weigh, measured unhitched | Trailer plate |
| GTM | Gross Trailer Mass | The weight carried on the caravan's own wheels when it's hitched up | Trailer plate (confirm at a weighbridge) |
| Tow Ball Mass | also "ball weight" (TBM) | The downward weight the coupling presses onto your tow bar | Ball scales or a weighbridge |
| Braked towing capacity | (braked) | The most you can tow when the trailer has its own brakes | Vehicle specifications |
| Unbraked towing capacity | (unbraked) | The most you can tow with no trailer brakes (capped at 750kg) | Vehicle specifications |
Every one of these is a manufacturer rating except payload, which you work out, and the actual loaded weights, which you only know once you put the rig on a scale. Hold that thought. It matters more than almost anything else in this guide.
The four definitions worth memorising are GVM (your car's limit), ATM (your van's limit), GCM (the combined limit), and tow ball mass (the bit that links them). The rest support those four.
Your tow vehicle's weights: tare, kerb, GVM and payload
Start with the car, because every towing decision flows from it. Four numbers matter, and two of them get mixed up constantly.
Tare and kerb both describe an "empty" vehicle, but they're not the same empty. Under the Australian Design Rules, tare is the vehicle with all fluids topped up except fuel, which sits at just 10 litres, and with no occupants and no accessories. Kerb mass is the more real-world version: a full tank, all fluids, ready to drive. On a ute with an 80-litre tank, the fuel alone is around 58kg of difference between the two. Diggermate spells this out well, and it catches people out because manufacturers don't all quote the same figure.
Why does this matter? Because the payload printed on or implied by your plate is usually calculated from tare. So the moment you fill the tank, you've already spent roughly 58kg of your budget before a single esky goes in the boot.
GVM, Gross Vehicle Mass, is the headline limit for the car. The NHVR defines it as the maximum loaded mass of the vehicle as specified by the manufacturer. Everything the vehicle carries counts towards it: you, your passengers, fuel, the bull bar, the drawers in the back, the water in the tank, and the tow ball weight of the caravan once you're hitched up. That last one surprises people. The weight pressing down on your tow bar isn't carried by the van. It's carried by your car, and it counts against your GVM.
Payload is simply what's left. Take your GVM and subtract the kerb mass and you've got the weight you're allowed to add. A dual-cab ute might show 600kg to 950kg of payload on paper. Sounds like plenty. Then you add a canopy, a second battery, recovery gear, a fridge, full water tanks, two adults and a dog, and a 300kg tow ball download, and suddenly that "plenty" is gone.
Here's the practical takeaway. Your accessories and your tow ball weight eat your payload first, before you've packed a thing for the trip. 4X4 Australia makes a sensible suggestion: aim to sit comfortably under your ratings, not right on the line, because the line is easier to cross than you'd think.
Your caravan's weights: ATM, GTM and tow ball mass
Now the van. This is where ATM and GTM cause more confusion than any other pair in towing, so let's settle it properly.
ATM, Aggregate Trailer Mass, is the most your loaded caravan is allowed to weigh. The federal Vehicle Standards Bulletin 1 (Revision 6, September 2024) defines it as the total mass of the trailer carrying its maximum load, measured when the trailer is not coupled to the car. It's the weight acting down through both the trailer's tyres and its coupling. In other words, the whole loaded van, standing on its own.
GTM, Gross Trailer Mass, is different. VSB1 defines it as the mass transmitted to the ground by the trailer's axles when it's coupled to the tow vehicle and carrying its maximum load. So GTM is only the weight sitting on the van's wheels once it's hitched up.
Here's the relationship that ties them together, and it's worth reading twice:
ATM = GTM + tow ball mass.
When you hitch the van to the car, some of its weight transfers off the van's wheels and onto the tow ball. That transferred weight is the tow ball mass. So the weight still on the van's axles (GTM) is always less than the van's total weight (ATM). The difference between them is exactly what's now pressing on your car.
A worked example makes it click. Say a van has a tare of 2,000kg and you load it to an ATM of 2,700kg. If 200kg of that is sitting on the tow ball when hitched, the GTM is 2,500kg. ATM 2,700, minus 200 on the ball, equals 2,500 on the van's wheels. Without a Hitch uses this same kind of breakdown, and once you've seen it laid out, you won't forget which is which.
One more thing, because it trips up newcomers. ATM and GTM are ratings stamped on the trailer's plate by the manufacturer. They're the limits, not your actual weights. Your real loaded weights could be higher or lower, and the only way to know is to weigh the van. We'll get to how shortly.
GCM: the number that ties it together (and trips everyone up)
If there's one weight that catches good, careful people out, it's this one.
GCM, Gross Combination Mass, is the most your fully loaded car and fully loaded trailer are allowed to weigh together. The NHVR defines it as the total maximum loaded mass of the tow vehicle plus any trailer it's towing. Simple enough on its own. The trap is what it does to the other numbers.
You can be under your GVM. You can be under your van's ATM. And you can still be illegal, because the two of them added together bust your GCM. GVM and ATM are each measured in isolation. GCM is the ceiling on both at once, and it's almost always lower than your GVM and ATM added together.
That means you usually cannot load your car to its GVM and tow a van at its full ATM. As you add weight to the car, the weight you can legally tow drops by the same amount. CarsGuide lays out the logic cleanly: a vehicle with a 2,500kg kerb, a 3,500kg GVM and a 5,000kg GCM can tow 2,500kg when it's empty, but only 1,500kg once it's loaded to GVM. The headline towing number and the full payload can't both be true at the same time.
Two real-world examples, both common Australian tow rigs. Treat the figures as illustrative and check your own plate, because they vary by model year and variant.
A Toyota LandCruiser 200 Series with a GVM of 3,350kg and a kerb of around 2,740kg has roughly 610kg of payload. Knock off a 350kg tow ball download from a big van and you're left with about 260kg for people, fuel, a fridge and everything else. Two adults and a full tank can almost use that up on their own.
A Ford Ranger Wildtrak with a 6,000kg GCM gives you another way to see the squeeze. To legally tow a 3,500kg van, the loaded Ranger can't weigh more than 2,500kg (6,000 minus 3,500). With a kerb around 2,250 to 2,280kg, that leaves only about 220 to 250kg of payload. So the famous "3,500kg tow rating" is real on paper, but the moment you actually load the van to 3,500kg, you've got almost no room left in the car. RV Buyers Guide and Loaded 4x4 both work through versions of this, and it's the single most useful thing to understand before buying a tow vehicle.
The lesson isn't "buy a bigger truck." It's that the tow rating on the brochure assumes an almost empty vehicle. Plan around your GCM, not the marketing number.
Tow ball weight: how much is right?
Tow ball weight (or tow ball mass) is the downward load your coupling puts on the car's tow bar. Get it wrong in either direction and the van becomes harder to control.
As a general guide, aim for around 10% of the loaded trailer's ATM, and treat 350kg as a hard ceiling on most light setups unless your tow bar and coupling are rated higher. RACQ frames 10% as a figure that generally shouldn't be exceeded; in practice the AU industry works within a band of about 8% to 15%, with 8% to 12% the sweet spot for stable towing. Whatever the percentage, defer to the lowest rated component: your vehicle, tow bar, coupling and hitch each have a limit, and the smallest one wins.
Too little ball weight and the van starts to sway, that horrible side-to-side snaking that can build until you lose the trailer. Too much and you overload the car's rear axle, lighten the steering on the front, and change how the car brakes. The rig can also start to pitch, the bouncing nose-up-and-down motion towing circles call "porpoising." RACV's towing guidance covers the same ground: load heavy items low and over the axle, and don't overload the rear. Neither extreme is where you want to be at 100km/h on the Bruce Highway.
Here's a quick reference for the 10% guide across common van weights:
| Loaded trailer ATM | 10% guide | Typical 8–15% band |
|---|---|---|
| 1,500 kg | 150 kg | 120–225 kg |
| 2,000 kg | 200 kg | 160–300 kg |
| 2,500 kg | 250 kg | 200–350 kg* |
| 3,000 kg | 300 kg | 240–350 kg* |
| 3,500 kg | 350 kg | 280–350 kg* |
*The 350kg cap applies to most light tow setups. Even where 15% would be higher, don't exceed 350kg or your tow bar/coupling rating, whichever is lower.
Remember where that ball weight goes. It doesn't vanish into the van. It lands on your car, counting against both your rear axle limit and your GVM. A 300kg ball weight can swallow half the payload of a typical dual-cab before you've loaded a thing. That's the quiet link between your van's weight and your car's legality, and it's why people who think they're fine often aren't.
Braked vs unbraked: when your trailer legally needs brakes
Trailer brakes aren't optional once you're past a fairly low weight, and the thresholds are set nationally.
An unbraked trailer is capped at 750kg for all light tow vehicles, full stop, regardless of what your car is rated to tow. Above that, the trailer needs its own brakes. For braked towing, where a manufacturer hasn't specified a figure, the common regulatory benchmark is 1.5 times the unladen mass of the tow vehicle, but the manufacturer's stated rating always governs when it exists.
| Trailer mass (loaded, by GTM) | Brake requirement |
|---|---|
| Up to 750 kg | No brakes required |
| 751 kg to 2,000 kg | Brakes required on at least one axle |
| Over 2,000 kg | Brakes on all wheels, plus a breakaway system that applies the brakes if the trailer disconnects and holds them on for at least 15 minutes |
These thresholds come from the Australian Design Rules and VSB1, administered by each state. Most caravans sit in the "over 2,000kg" band, which is why they run electric brakes and a breakaway battery. If you're shopping for a camper trailer or box trailer near the 750kg line, this is worth checking before you buy.
The "lowest rated component" rule applies here too. Your car might be rated to tow 3,500kg, but if your tow bar or coupling is rated lower, that lower number is your real limit. RACQ is blunt about it: the combination is only as strong as its weakest towing-related part.
The GVM upgrade myth: why more payload can mean less towing
This is the section that surprises people, so let's be precise.
A GVM upgrade lets your vehicle legally carry more. New springs, sometimes new shocks, and a fresh compliance plate with a higher GVM. What it usually does not do is raise your GCM or your towing capacity. 4WDing Australia and the road-safety program Truck Friendly both make the same point: don't assume a GVM upgrade lifts your braked towing capacity, your tow ball download limit, or your GCM. Most don't.
Run the maths and it gets worse than "no change." Say a GVM upgrade lifts your GVM from 3,000kg to 3,220kg, but your GCM stays at 5,950kg. Your maximum towing capacity at full GVM is now 5,950 minus 3,220, which is 2,730kg. That's well down on the original 3,500kg rating. By using the extra payload the upgrade gave you, you've eaten into what you can legally tow. More carrying capacity, less towing capacity, unless the GCM is also revised.
There's history here worth knowing. In October 2018, the Commonwealth's vehicle safety standards branch wrote to suspension manufacturer Lovells to clarify that they had never held GCM upgrade approvals, only GVM ones. Truck Friendly documents that correspondence. The position has moved on since: a small number of GVM kits now come paired with an approved GCM revision, and Lovells today lists specific GCM revisions. So the honest, current picture is this. GVM upgrades are common and legitimate. Genuine GCM increases are rare, separate, and only valid when a manufacturer holds a specific approval for your vehicle. If a salesperson tells you an upgrade lets you "carry more and tow more," ask to see the GCM approval in writing.
There's also a registration wrinkle. A GVM upgrade fitted before the vehicle is first registered (a Second Stage Manufacture approval) gets federal sign-off and is recognised nationwide. One done after registration is a state-based engineering certification, and the rules vary between states. Worth confirming before you spend the money.
Is it illegal to tow overweight in Australia? Penalties by state
Short answer: yes, and the penalties are real. The longer answer fixes a mistake almost every blog on this topic makes.
Most caravans and trailers (anything with an ATM of 4.5 tonnes or less) are governed by state road law and the federal Australian Design Rules, not by the National Heavy Vehicle Regulator. The NHVR and the big numbers you'll see quoted around it (mass-breach fines that climb past $5,000 and into the tens of thousands) apply to heavy vehicles, which the NHVR defines as those over 4.5 tonnes GVM or ATM. Big American rigs and fifth-wheelers can cross that line. Your average dual-cab-and-van combination does not. So if an article scares you with a $22,000 fine for an overweight caravan, it's quoting the wrong rulebook.
The penalties that actually apply to light setups are set by your state or territory. They're smaller, but they come with demerit points and, in serious cases, a defect notice that takes your rig off the road until it's fixed.
| State / Territory | Indicative penalty for overloading | Demerit points |
|---|---|---|
| NSW | Around $469 per offence (indicative) | 3 |
| QLD | Around $333 per offence (indicative) | 3 |
| VIC | Around $238 to $1,580 depending on severity (indicative) | Varies |
| SA, WA, TAS, ACT, NT | State-based fines apply, several with demerit points | Varies |
Treat those figures as indicative, not gospel. They're compiled from weighing services and news reports, they change most years, and they vary with how far over you are. Before you rely on a number, check your own state road authority. The point isn't the exact dollar figure anyway. It's that being overweight is an offence everywhere in Australia, and enforcement is getting tougher: Queensland police now carry portable scales and issue fines where they used to give warnings, and a NSW roadside operation found close to 40% of caravans were overloaded.
Then there's the part that hurts more than any fine. Insurance. If you have an accident while overweight, your insurer can decline the claim, because an overloaded vehicle is treated as unroadworthy, and unroadworthiness is a standard exclusion. CIL Insurance, through its Without a Hitch site, is upfront that claims can be refused when a van is loaded beyond the ATM or ball weight on its plate, or towed by a vehicle not rated for the job. A $400 fine is annoying. A declined claim on a $90,000 van after a rollover is life-changing.
Why compliance plates can't be fully trusted, and how to weigh your rig
Here's the catch that undoes a lot of careful owners. You can do all the maths off your compliance plate and still be wrong, because the plate itself may be inaccurate.
The Caravan Council of Australia has estimated that around 90% of caravan and camper-trailer makers and importers have plates that aren't fully compliant, often with inaccurate tare and empty ball-loading figures. That's an industry-body estimate rather than a measured audit, so take it as a strong warning rather than a hard statistic. But the implication is the same either way: the only way to know what your rig actually weighs is to put it on a scale, loaded the way you really travel.
How overweight is the fleet? Honestly, the data is messy. RACQ has estimated around half of caravans are overweight (that figure is from 2019). Roadside police operations have reported anywhere from 40% to as high as three-quarters overweight on at least one measure, depending on where and when they weighed. The numbers bounce around because everyone measures differently. The safe conclusion: a lot of vans are over, and assuming yours isn't is a gamble.
So weigh it. You've got three main options.
A public weighbridge is the cheap path. You'll do a few passes to get the full picture: the whole rig together, then just the van's wheels for GTM, then the tow vehicle on its own. It gives you actual axle and combined weights, though it won't directly read your tow ball mass without a separate measure. RACQ recommends weighbridges for exactly this reason.
A mobile caravan weighing service is the thorough path. They come to your home or storage and measure axle, tow ball and combined weights, hitched and unhitched, then hand you a written compliance report. Cost runs roughly $150 to $450 across Australia depending on operator and location. For a van you're about to take around the country, that's cheap insurance. (TTWeigh, one of iCheckTPMS's stockists, is itself a caravan weighing business, which makes for a tidy one-stop "weigh it, then keep an eye on it" approach.)
For tow ball mass at home, you have two DIY methods. Dedicated tow ball scales are the accurate option and handle up to around 300 to 350kg. The cheaper trick uses bathroom scales and a plank: set the scales and a brick of equal height 90cm apart, lay a plank across them, rest the coupling at the 60cm mark, read the scales and multiply by three. Get the geometry right or the answer's meaningless, and note that most bathroom scales tap out around 130 to 150kg, so heavy vans will read off the scale. For those, use proper ball scales.
When should you weigh? Loaded for a real trip, with full water, full fuel, the lot. An empty van tells you nothing useful about how you actually travel.
What your weights do to your tyres and bearings (the bit nobody mentions)
Most weight guides stop at the law. But the reason these limits exist isn't to give police something to fine you for. It's because weight does real, physical things to the two parts of your rig most likely to fail on a hot highway: your tyres and your wheel bearings.
Start with tyres. Every tyre has a load rating, and Australian rules require your tyres to carry a load index at least equal to your placard. Push past what a tyre is built to carry, or run it under-inflated for the load, and it builds heat. Tyrepower Australia puts it plainly: overloading a tyre, or running it at lower-than-specified pressure, causes heat build-up that can destroy the tyre. Toyo's Australian technical notes say the same thing in different words: under-inflation cuts the tyre's effective load capacity while pushing its operating temperature up. An overloaded tyre behaves like an under-inflated one. More flex in the sidewall, more friction, more heat, and eventually a blowout. Heavier loads also need higher pressures to start with, which is one more thing to get right and keep an eye on.
Now the bearings, which get talked about even less and arguably matter more. Your wheel bearings carry the van's weight through the hubs. Load each hub beyond its rating and the hubs run hotter. Enough heat and the grease breaks down, the bearing fails, and in the worst cases the wheel separates or the hub catches fire by the roadside. As a rough touch test, a hub that's warm (around 55 to 60°C, comfortable to hold a hand on) is normal; one too hot to touch (past about 90°C) is a warning. The trouble is you can't feel any of this from the driver's seat until it's too late.
That's the real argument for monitoring. You weigh the rig once to get it legal and balanced. Then you monitor it continuously, because pressure, tyre temperature and bearing temperature all change as you drive, load up, air down and climb into the heat. You simply can't see them otherwise.
This is where a tyre pressure monitoring system earns its place. An iCheckTPMS kit reads the pressure and temperature of every tyre and shows it on a solar-powered display, updating every five minutes whether you're rolling or parked up at camp (the brand calls this InstaData™). Setup is close to zero thinking: you screw the sensors onto cold tyres and IntelliData™ sets the alarm thresholds for you, so you're not punching in numbers. For a 4WD towing a single-axle van the IC008 eight-sensor kit covers car, van and spares; for a dual-axle van the IC010 ten-sensor kit does the job.
The bearing side is where iCheckTPMS does something the others don't. Its wheel bearing temperature sensors are physically mounted on the hub and report hub temperature on the same display as your tyres. That's a real, distinct sensor reading the bearing, not a guess inferred from a valve-stem cap. Given that overloaded hubs are exactly what overheats, having that number in front of you closes the loop between "I loaded the van heavy" and "I'll know before it lets go." Pair this with our 4WD tyre pressure guide for the pressure side, and the pre-trip caravan safety checklist for everything else.
Weight, in other words, isn't just a paperwork problem. It's a tyre problem and a bearing problem, and those are the ones that strand people.
Special cases: boat trailers, horse floats, camper trailers and EV tow vehicles
The same rules apply across every kind of trailer, but a few setups have their own quirks worth a mention.
Boat trailers spend their lives backing into salt water, which is hard on bearings and brakes. Many smaller ones sit under the 750kg unbraked line, but a loaded tinnie plus fuel, batteries and gear adds up faster than people expect, so check the axle and tyre loads.
Horse floats carry a live load that moves. A horse shifting its stance changes your ball weight on the fly, and an underinflated or overloaded float gives the animal a rough, unsafe ride. The weight principles are identical; the variable is that your load literally walks around.
Camper trailers have lower ATMs, which lulls people into a false sense of safety. They're easy to overload with water, a fridge, recovery gear and a rooftop tent, and a small trailer at 120% of its ATM is just as illegal as a big van.
EV and plug-in hybrid tow vehicles change the maths before you've loaded a thing. Battery packs are heavy, so the kerb mass is high and the payload and GCM headroom can disappear quickly. Many EVs also carry lower tow ratings and GCMs than the diesel equivalents. None of that makes them bad tow vehicles, but it does mean you should read the plate carefully rather than assuming a big, powerful vehicle has big towing numbers to match.
Different trailers, same discipline. Know your numbers, weigh the loaded rig, and keep an eye on the tyres and bearings once you're moving.
Where the kilos actually go: a worked payload budget
It's easy to nod along to "watch your payload" and still get a shock at the weighbridge. So let's actually spend a payload and watch it disappear. The numbers below are illustrative, and yours will differ, but the shape of it is real for a lot of touring setups.
Take a dual-cab ute with a GVM of 3,200kg and a kerb mass of 2,300kg. That's 900kg of payload to play with. Sounds generous. Now load it for a trip:
- Bull bar and winch: 80kg
- Rear drawer system and fridge slide: 60kg
- Second battery and solar gear: 30kg
- Recovery gear, tools, jack: 40kg
- Onboard water (40 litres): 40kg
- Two adults: 160kg
- Clothes, food and camping gear: 90kg
- Tow ball weight from the van (around 250kg): 250kg
Add that up and you're at 750kg of an available 900kg. You've got 150kg left, and you haven't packed the kids, the dog, or the camp kitchen yet. Notice the single biggest line: the tow ball weight at 250kg, more than a quarter of the entire budget, gone to the van before you loaded anything for yourself.
That's the whole point of doing this on paper before you do it at the weighbridge. The payload that looked like plenty was mostly committed before the fun stuff. Most people find their accessories and ball weight have quietly eaten two-thirds of the budget, and the only question left is how disciplined they are with the rest.
Already overweight? Here's how to get back under
If you weigh your rig and find you're over, don't panic and don't ignore it. The fix depends on which limit you've busted, so step one is knowing whether it's your car's GVM, the van's ATM, an individual axle, the tow ball, or the combined GCM. Each points to a different solution.
Redistribute before you remove. Often the total is fine but the balance is off. Moving heavy items in the van so they sit over or just ahead of the axles (rather than at the back) changes your tow ball weight and can pull an overloaded rear axle back into line. In the car, keep heavy gear low and central. Sometimes you don't need to take anything out, just put it in a smarter spot.
Cut your water. Water weighs 1kg per litre, and it's the easiest weight to manage. Travelling with a 150-litre tank full is 150kg riding around for no reason if there's a tap at the other end. Fill closer to camp and you've freed up serious payload instantly.
Do an honest gear audit. Everyone tows a "might need it" pile. The second spare you've never used, the third camp chair, the toolbox that could be half the size. It adds up fast.
Consider a weight distribution hitch, but understand its limits. A WDH spreads some of the tow ball load back across the van's axle and the car's front axle, which improves steering feel and reduces sag. What it does not do is raise any legal limit. You're still bound by your GVM, GCM, ATM and ball rating. A WDH is a balance and comfort tool, not a get-out-of-overweight card.
A GVM upgrade can help, with the GCM caveat. As covered earlier, more payload is genuinely useful, just don't assume it lets you tow more. Check the GCM.
If after all that the van is simply too heavy for the car, the honest answer is that you've got the wrong combination. Either a lighter van or a tow vehicle with more capacity. It's not what anyone wants to hear, but it beats a declined insurance claim.
Your pre-trip weight checklist
Before every big trip, run through this. It's the whole guide boiled down to actions.
- Find your four limits: GVM and GCM on the vehicle's compliance plate, ATM and GTM on the trailer plate.
- Weigh the rig loaded the way you actually travel, with full water, fuel and gear, at a weighbridge or with a mobile weighing service.
- Check the car sits under its GVM, the van under its ATM, and the two combined under your GCM.
- Check each axle is under its own rating, not just the totals.
- Measure your tow ball weight: aim for 8 to 15% of the van's ATM, and stay under 350kg or your tow bar and coupling rating, whichever is lower.
- Confirm your tyres' load rating meets the placard, and set pressures for the load you're carrying.
- Test the trailer brakes, and on anything over 2,000kg, the breakaway system.
- Don't take the plate's tare and ball figures on trust. The scale is the only number that counts.
- Re-weigh after any big change: new drawers, an extra water tank, a different van.
- On the road, keep an eye on tyre pressure, tyre temperature and hub temperature, so a problem shows up as a number rather than a noise.
Frequently asked questions
What's the difference between ATM and GTM?
ATM (Aggregate Trailer Mass) is your loaded caravan's total weight, measured when it's unhitched and standing on its own. GTM (Gross Trailer Mass) is the weight carried on the caravan's axles when it's hitched to the car. The gap between them is the tow ball mass that transfers onto your tow bar, so GTM is always lower than ATM.
How much should my tow ball weight be?
Aim for around 10% of your loaded trailer's ATM, within a practical range of about 8% to 15%. Never exceed 350kg on most light setups, or your tow bar and coupling rating if it's lower. Too little ball weight causes the van to sway; too much overloads your car's rear axle and lightens the steering.
What's the difference between tare and kerb weight?
Tare is the empty vehicle with only about 10 litres of fuel and no accessories or occupants. Kerb weight is the more realistic figure, with a full tank and all fluids. On an 80-litre tank the difference is roughly 58kg, which matters because your payload is usually calculated from tare, so filling up spends some of it before you load anything.
Does a GVM upgrade increase my towing capacity?
No. A GVM upgrade raises how much your vehicle can carry, but it doesn't automatically lift your GCM or braked towing capacity. Because the heavier vehicle uses up more of your fixed GCM, an upgrade can actually reduce how much you can legally tow. Only a separate, vehicle-specific GCM revision changes the towing side, and those are far less common.
Is it illegal to tow an overweight caravan in Australia?
Yes. For caravans under 4.5 tonnes it's a state offence (not an NHVR matter), with fines and demerit points that vary between states, plus the risk of a defect notice that grounds your rig. Being overweight can also let your insurer decline a claim, because the rig is considered unroadworthy. Check your own state road authority for current penalties, as they change.
Can I be over my GCM even if my GVM and ATM are both legal?
Yes, and it's the most common mistake people make. GCM is a separate ceiling that's almost always lower than your GVM and ATM added together. So a fully loaded car and a fully loaded van can each be legal on their own, yet illegal the moment they're combined.
How do I weigh my caravan?
Use a public weighbridge, doing separate passes for the whole rig, the van's wheels and the car on its own, or book a mobile caravan weighing service (around $150 to $450) that measures axle, ball and combined weights and gives you a report. Either way, weigh it loaded the way you actually travel, with full water and fuel.
Where do I find my weight limits?
Your vehicle's GVM and GCM are on its compliance plate (usually in the driver's door jamb) and in the owner's manual. Your caravan's ATM, GTM and tare are on the trailer's plate. Remember these are the manufacturer's rated limits, not your actual weights, so you still need to weigh the loaded rig.
At what weight does a trailer need brakes?
Up to 750kg, no brakes are required. From 751kg to 2,000kg, the trailer needs brakes on at least one axle. Over 2,000kg, it needs brakes on all wheels plus a breakaway system that applies the brakes if it disconnects. Unbraked trailers are capped at 750kg regardless of what your car can tow.
Can my tyres handle my loaded towing weight?
Only if each tyre's load rating meets or exceeds the actual weight on its axle, and it's inflated correctly for that load. Overloading or under-inflation makes a tyre run hot, which is the main cause of blowouts. That's why monitoring pressure and temperature on every wheel, including the van's, is worth doing once you're carrying a full load.
The one habit that ties it all together
If this guide leaves you with a single action, make it this: weigh your loaded rig, then check it against the four numbers that matter, your GVM, your van's ATM, your GCM, and your tow ball weight. Most people who think they're fine have never actually done it, and a fair few get a surprise when they do.
Getting legal is a one-off job. Staying safe is ongoing, because the weight you're carrying keeps working on your tyres and bearings every kilometre you drive. Weigh it once. Then let a tyre pressure and bearing monitoring setup watch the parts you can't see, so the only surprises on your trip are the good ones. Travel with confidence, and protect more than just your tyres.
Weights, penalties and regulations referenced here were current at the time of writing (2026) and vary by state. Always confirm figures against your vehicle's compliance plate and your state road authority before relying on them.
