Caravan Tow Weights Explained
(with real life examples)
Published: 23 Jan 22 Updated: 28 Sept 22
When it comes to towing, getting your vehicle and trailer weights right is one of the most crucial places to start. Discussion around tow weights often brings feelings of unease. Firstly because it’s confusing…ATM, GCM, GTM, TBM, GCM…we haven’t seen so many acronyms since high school Maths! There’s also a lot at stake when it comes to complying with weights. Being overweight puts strain on your vehicle’s drivetrain, chassis, suspension and brakes. It also becomes extremely difficult to control, which in turn can put yourself and other road users in danger. It can be a costly exercise if you get it wrong (as we have found) and you’ve probably also heard that if you’re in an accident, your insurance company will weigh your setup and void your policy if you’re overweight in any of the many weight categories.
In this article, we’re going to visually show all of the weights related to your tow setup and explain what they mean, where to find them, what can be upgraded and other important tidbits of information relating to each one. We then put that all in context by talking you through our own weight journey that we went on when we set up our rig to tour Australia. Stick around until the end where we list some of the most reputable weight companies as recommended by fellow travellers in the community.
This information can be a lot to digest. Our mates at Check Weighthave put together an awesome online coursebreaking down this topic. Their $97* course is broken down into 5 parts. In total these parts contain 35 minutes of video which is easy to understand, very thorough and professionally presented. 17 downloadable PDFs explain each section of the course in detail with what you have just learnt on video. We highly recommend this course and you can check it out here.
The two main takeaways from this article are:
Know your weights.
Check your weights.
So let’s jump into that first point and understand what all those acronyms mean!
Caravan Weight Acronyms:
Caravan Tare Weight (TARE)
The weight of your caravan as it leaves the factory new but with empty water tanks and gas bottles.
You can find your caravan’s TARE on the vehicle plate or in the manufacturer’s handbook.
If you’re buying a second hand van, you also need to consider what extras the original owner added to the van that may not be included in its listed tare weight. For example, an extra spare wheel, sway bars, solar panels, suspension upgrade etc
Your TARE is calculated when the caravan manufacturer puts your caravan over the scales on completion of its build and then records this weight.
Aggregate Trailer Mass (ATM)
The maximum weight your caravan can legally be when fully loaded and unhitched from the tow vehicle. This includes the tare weight plus everything else you put in your caravan.
You can find the maximum ATM for your caravan on the vehicle plate or in the manufacturer’s handbook.
Your ATM is measured by placing scales under the caravan’s wheels and adding on the towball weight.
You may be able to upgrade your ATM by visiting an engineer who’s also accredited with the relevant state authority.
The difference between your caravan’s ATM and TARE weight will equal your payload. Payload is how much stuff you can put in/on your caravan including water, gas, food, drinks, belongings, tools, bikes, firewood etc.
Be careful if your caravan’s tare and ATM only have a small difference between them eg 300/400kg. This is not a lot of payload, especially if you’re going to be doing any free camping. Think if your water tanks carry 200L of water, that’s 200kg of payload you’ve already used up. Everyone always says it and we’ll jump on that bandwagon too from our own experience…you will be so surprised at how much individual items weigh and how quickly it all adds up!
Towball Mass (TBM)
The weight the caravan imposes onto the vehicle’s towball.
You can find your TBM by purchasing a tow ball scale or getting a professional weight check company to come and weigh you - more on these companies further on.
This is one of the most confusing but important weights. It’s important because your TBM is included in your vehicle’s GVM (see GVM explanation below). If you’re already getting close to your GVM, adding an extra couple hundred kilos on for your TBM will often send you straight to being overweight.
The TBM can be confusing because it changes depending on how much is in your caravan and how you’ve loaded it. As a general rule, your TBM should be between 6-10% of the weight of your fully loaded caravan (see ATM above).
However, you also need to check your vehicle’s tow ball rating to ensure your TBM is less than your vehicle’s legal limit, which is usually 10% of your caravan’s towing capacity (see BTC below).
Gross Trailer Mass (GTM)
A measure of the weight the fully loaded caravan imposes on its wheels and axles when hitched to the tow vehicle.
You can find the maximum GTM for your caravan on the vehicle plate or in the manufacturer’s handbook.
Your GTM is calculated while putting scales under the caravan wheels while hitched to the tow vehicle.
This is similar to the caravan’s ATM. The difference is:
GTM - maximum weight of caravan when hitched to the vehicle, therefore the towball mass isn’t included because that’s now on the vehicle’s GVM.
ATM - maximum weight of caravan when unhitched. The towball mass is included for this calculation.
Vechile Weight Acronyms: (table)
Gross Vehicle Mass (GVM)
The maximum weight your vehicle can be when it’s fully loaded. This includes the base weight of the vehicle plus fuel, water, passengers, belongings, any modifications you’ve added and if you’re towing, it also includes your towball mass(TBM)!
The manufacturer specifies the GVM and it can be found in your vehicle’s handbook.
You can calculate your GVM by putting your vehicle over a weigh bridge or using scales under the wheels.
You can legally upgrade your GVM in Australia and it’s often strongly encouraged if you’re going to be regularly towing. It is just so easy to chew up your GVM. Check out this real life example of the troubles Lapping the Island had with their GVM weight in both their 200 Series Landcruiser and Ford F350. You can read about their experience in this article here.
Vehicle Tare Weight (TARE)
The total weight of the vehicle empty from the factory. This does not include fuel.
You can find this weight in your vehicle’s handbook.
Your TARE is calculated when the vehicle manufacturer puts your new vehicle over the scales on completion of its build and then records this weight.
The difference between your vehicle’s GVM and TARE will equal your payload. Payload is how much stuff you can put in/on your vehicle including modifications, fuel, water, belongings and don’t forget: PASSENGERS!
Kerb Weight
This is the vehicle tare weight plus a full tank of fuel. The name ‘kerb weight’ comes from the thought that your new vehicle is parked on the kerb, ready for you to take off in it, without having loaded any gear or made any modifications.
This can be found in your vehicle handbook, or on your purchase papers if buying new.
Gross Combination Mass (GCM)
The total weight your vehicle and caravan/trailer can be when they are hitched together and both fully loaded.
The manufacturer specifies the GCM and it can be found in your vehicle’s handbook.
You can calculate this by taking your whole setup over a weigh bridge while fully hitched and loaded, or get a professional mobile weight company to come out to weigh your setup (more on them at the end of the article)
The golden question is can you upgrade your GCM? The answer is hazy! At the time of writing, the best information can be found from this article by Truck Friendly which was last updated 16/5/22. We did a bit more digging and found this post by Lovells Automotive Systemsfrom September 2021 which includes each state’s stance on GCM modifications. Basically, if you’re buying your vehicle new, you should be able to get a GCM upgrade pre-registration in all Australian states and territories. Post registration GCM upgrades are a different story and are only legal in some states and territories.
Another thing to consider is that these second stage manufacturers who perform the upgrades (eg Lovells) don’t have the upgrade kits available for every vehicle type. So even if a GCM upgrade is legal in your state, you still need to check if manufacturers can actually upgrade your chosen tow vehicle.
This weight can often be a killer and we were one of the ones that fell victim to it. Read about it in our real life case study below. The tricky thing is your vehicle might have a GVM of 3000kg and can tow 3200kg, so you might be thinking your GCM is 6200kg. However the GCM is usually lower eg 5700kg…That’s 500kg less! Therefore you can’t even legally load up your car to its GVM or caravan to its BTC.
Braked Towing Capacity (BTC)
This is the maximum weight that your vehicle can legally tow when an electric brake controller has been fitted to the vehicle. In other words, the total weight your caravan/trailer can be when fully loaded (the ATM of the caravan/trailer).
The manufacturer specifies the BTC and it can be found in your vehicle’s handbook.
It’s important to note that your BTC may reduce if you get a GVM upgrade. This is because the GCM usually still remains the same. So let’s say for example your GCM is 7000kg. If your GVM is 3200kg and you want to upgrade it to 3500kg, that’s an extra 300kg you’ve added but the GCM is still only 7000kg. This means if you want to load up your vehicle all the way to its new GVM of 3500kg, that extra 300kg needs to be taken off the BTC so that your combined weight doesn’t exceed 7000kg. Think of it like a seesaw effect.
Our Weight Dilemma
Now that was a lot of acronyms to remember! Don’t worry, once you start applying this to your setup, it starts making a lot more sense. That’s why we’re going to run through our tow rig weight journey now to help give more real-life context when understanding what all this means.
We decided we wanted to travel around Australia in a caravan and the time had come to find ourselves a tow vehicle. Personally, we were pretty set on getting a Toyota and our initial pick was a Prado. The Toyota Prados could tow 2.5 tonne (the new ones have since been upgraded to 3 tonne) and we began thinking that might be a bit limiting, especially hearing many say you don’t want to tow right on your limit. The caravans we were looking at that had ATM’s of 2.5 tonne had tiny payloads, so we were more realistically looking at an ATM around 3 tonne. We said goodbye to the idea of a Prado and changed our focus to the Hilux.
We found ourselves an awesome 2019 SR Toyota Hilux which we purchased at the beginning of 2021. It could tow 3.2 tonne which was more than enough for what we needed…right?! We spent the best part of 2021 setting up our Lux for the big lap. We added on extra modifications like a snorkel, lights and solar panel, we upgraded the suspension, put on some bigger all terrain tyres and spent countless hours on the weekends fitting out the canopy with draws, boxes, carpet, battery systems etc. The hard work was worth it though because we were going to be travelling around Australia in this thing soon right?
WRONG! No we would not! …Okay so what happened?
The secondhand caravan market was crazy. Out of the blue we were put in touch with a lovely couple selling their immaculate Kedron caravan. Being a Kedron, it wasn't all that lightweight but the condition and layout of the caravan, plus the timing, was just perfect for us so we had to jump at the opportunity.
Getting a heavy, full off-road caravan like a Kedron was initially never on the cards for us. But once it became an option, we obviously couldn’t resist and began preparing ourselves for the fact that we’d probably have to upgrade our tow vehicle. The Kedron we found was a 2016 XC3 Cross Country model. These were designed to be a lighter alternative to your typical Kedrons and were able to be towed by the likes of Prados and Hilux’s. Our Kedron had a TARE of 2450kg and ATM of 3500kg. The Lux can tow 3200kg but that still left us with about 700kg in payload. It was sounding good so far!
That was until we hit the next hurdle - the Gross Combined Mass. The GCM of the Hilux was 5650kg. Now to show you why that was a bad thing, let’s have a look at these stats:
Hilux GVM - We weighed ours and it was 2800kg.
Hilux GCM - 5650kg. If the vehicle was weighing 2800kg, that left us 2850kg for the caravan. Knowing that the caravan’s TARE was 2450kg, we would have a payload of 400kg. Now this is on the lower side but also doable. We just weren’t sure how much payload we would actually need to use. As soon as we picked up the Kedron, we took it to a weighbridge to find out where we were at.
The results were in and it wasn’t good. We were at a GCM of 5660kg - 10kg over and the only thing we had put in the caravan was water! So where did the weight come from? Well water alone counted for about 300kg. The caravan also had an additional spare tyre, as well as a weight distribution hitch and bars fitted, which account for a fair bit of extra weight. We were on holidays at the time so had a lot of our belongings in the car too. We’d prepared ourselves for this to probably happen but it still really stung. Thankfully we were 7 months out from starting our trip so we had time to fix this issue.
Onwards & upwards! Our focus changed again and now we were looking at the ultimate tow vehicle from Toyota - a Single Cab 79 Series Landcruiser! We purchased our next rig a year after we purchased the Hilux and now were the proud owners of a 2014 79 series Landcruiser. Having shot ourselves in the foot with the Hilux, we analysed and checked every single weight we could think of before we made this purchase. Here are the stats:
79 Series GVM: 3630kg (The vehicle we purchased has had a 10% GVM upgrade certified). We had it weighed professionally before purchase and it came in at 3020kg with a full tank of diesel plus its 70L water tank filled to the brim. We then added an estimate of 560kg to count ourselves as passengers (160kg), our fridge and draws (100kg) and the TBM from the caravan (300kg). This brought the new estimate of the ute to 3580kg - 50kg under its GVM and with all modifications we would want already added, you beauty!
79 Series GCM: 6800kg (that’s over 1100kg more than what we had with the Hilux!). Now let’s say we fully load up the caravan (I doubt we’ll have that much stuff in it but we’re provisioning for worst case scenarios here!), that would be 3500kg. We then add that to the weight of the ute: 3280kg* and we’re at a GCM of 6780kg. We’re under!!! But only by 20kg and that’s with a 79 Series! It’s crazy to think how many setups out there must be overweight, especially when you’re looking at adding rooftop tinnies and bigger vans (our caravan is only 18 foot in length!).
*For the purpose of calculating the GCM, we put the 300kg from the tow ball back onto the caravan.
Final Rig Weigh in Day before our big lap:
Predictions are one thing but actually getting your setup professionally weighed is so important to see exactly where you’re at with weights. Once we finally loaded up the cruiser and caravan ready for our trip, we got John from Ezi-Weigh on the Gold Coast to come and weigh our setup a week before we hit the road for good. Read through how we went below.
Overall we were stoked with our results! Kedron caravans are HEAVY and we had just condensed our whole life into this setup. Statistics from QLD police also show that 90% of caravanners are overweight in some form, so your chances of not complying are pretty high!
You’ll notice we ticked off 6/7 weight categories you need to comply with. We fell short on the vehicle’s GVM when the caravan was hitched, which was 43kg over. However we were 250kg under in the caravan’s ATM and we still had 200kg up our sleeve in the weight of our entire setup (GCM), meaning we had an easy fix for this problem. We just had to move some weight from the ute into the caravan. Brad had a lot of spare parts in the back of the ute so he moved them, along with some tools, into the caravan toolboxes instead.
Now that we’ve actually hit the road and have been travelling full-time for a few months, we understand that our weights are always fluctuating. You can feel it when you drive off after a big shop or when you’ve filled the tanks up from empty. It’s a good idea to drive over a weigh bridge every now and then on your travels to give yourself a little recalibration. We went over one recently and our GVM was back up to 3640kg (10kg over). It was a good reminder to shift things from the ute to the caravan again (we have a habit of leaving cartons of beer in there). You also tend to accumulate a few extra things in your first few months of travelling as you settle into being on the road full-time, so it’s a good idea to be mindful of that and counteract it by shedding the gear you don’t need while you’re at it. Yes, you will always bring too much stuff!
Have you weighed your setup?
That brings us to the second takeaway of this article. Check your weights! And no that doesn’t mean estimating how much you think you weigh! Take your rig over a weigh bridge at a minimum but ideally, get a professional to do a weight check for you. Getting a professional to weigh your setup, in our opinion, is invaluable and essential to know before starting your trip. There are a few great mobile weight companies that will come to you, weigh your rig and give you a comprehensive report showing how you’re meeting all of the weight compliances to be legal. They will even provide suggestions on how to reload your caravan if some of your axle loadings are a bit off. These guys usually cost a couple hundred dollars and it is money well spent to know that a) you’re legal and b) you can have peace of mind knowing that if you have an accident, your insurance will still cover you. You wouldn’t not insure your van, so don’t unknowingly void your insurance by being overweight.
Here are the most recommended companies according to the travel community, depending on where you’re based:
SE QLD - Ezi-Weigh Professional Mobile Caravan & Vehicle Weighing
SE QLD - Weightcheck Mobile Caravan Weighing
SE QLD -Mobile Weight Check
Central Coast/Newcastle/Mid North Coast*, NSW - Check Weight
*These guys have also just opened up their first franchise in Sydney.
Sydney, NSW - Your Weigh Mobile Vehicle Weighing
VIC - Weighstation
NT - The Territory Weigh
If you’ve had a great experience with a mobile weight check company, comment below your recommendation!
Throughout our journey with tow weights, we found it really interesting and helpful hearing about other's experiences with their particular set up. It gave us better understanding when we could see the acronyms put into context, it prompted us to check weights we may have overlooked and it also provided a great insight into what individual items can weigh. We hope you found us sharing our real life example helpful. We’ve also linked a video here from Now or Never which showcases their experience with getting their Ford Ranger and JB Gator X caravan weighed, finding they were overweight and the process of culling a lot of belongings!
If you’ve also shared your tow set up situation somewhere, contact us here so we can also add you to this article!
We feel like we’ve had our heads in this weight game a lot over the past few months so if you have any thoughts or questions, please pop them in the comments below!