Understanding caravan weights can feel a bit overwhelming, however, if you are looking to join the many people travelling around Australia in a caravan, I would strongly recommend you take the time to get your head around this subject.  Ideally before making decisions and purchasing a tow vehicle and caravan.  In this article I will do my best to demystify the subject of caravan weights and after reading, I hope you will have a better understanding of what all the acronyms mean and what you need to know before you go out and pick your car and caravan.

Caravan weights, in a general sense, refer to the various measurements (see fig. 1.) that quantify the mass of a tow vehicle and caravan.  In Australia, it’s important to know and follow weight limits for several reasons.   Caravan weight will impact performance, including braking and manoeuvrability. Being overweight can result in fines, penalties, and insurance problems if there’s an accident and claim needs to be made. So, paying attention to caravan weights isn’t just about safety, it’s also about following the law and allowing peace of mind when it comes to insurance.

So what are the key weights that you need to understand, I have prepared a diagram to help you visualise the key compliance requirements when it comes to caravan weights.  Each of these acronyms will have a limit as set by either the vehicle or caravan manufacturer.

 

Choosing your tow vehicle

Now that we have an understanding of all the acronyms lets have a look at how we should be thinking about choosing a tow vehicle.  The manufacturers are very misleading in their marketing, something you will hear from the sales man is the maximum tow rating.  Let me explain why you shouldn’t be using this value alone to guide you on your choice vehicle and caravan.

Let’s take the very popular Land Cruiser 200 series (LC200).  They have as standard a maximum tow rating of 3500kg.  A LC200 comes standard with a GVM limit of 3350kg.  The Kerb Weight of an LC200 series is 2740kg.  To work out the pay load we can subtract the Kerb Weight from the GVM (3350kg-2740kg=610kg).  So the LC200 has a payload of 610kg, sounds good right.  Well now lets consider what we have added, It’s not uncommon at all for a tourer to be fitted with a bull bar, a winch, a secondary battery system, a fridge, some draws, some tools and recovery gear.  Lets give all this a very
conservative estimate of 200kg (touring equipment of this nature could easily exceed 400kg).  Now we have Fuel 90kg,  Passengers 2 x 80kg (even more if you have kids).  If you then choose a 3500kg Caravan, you will be placing the tow ball mass onto the vehicle, TBM should be around 8-10% of the ATM so lets say its 350kg.  (200+90+80+80+350 = 800kg).  We are now over our GVM by 190kg (theoretical payload 800kg – payload limit 610kg = + 190kg).

It is worth mentioning that there are often options available to increase the GVM rating and the above calculations should highlight why this might be necessary.   In the LC200 series example it is possible to upgrade from 3350GVM to 3800kg.  This would give the vehicle a payload of 1060kg (3800kg – 2740kg = 1060kg).  So, in this example the payload limit is now 1060kg, our theoretical
payload was 800kg (800-1060= – 260kg), the vehicle is now with in its limits by 260kg.

So we managed to get our theoretical example compliant on GVM, but still there is more.  Now our GCM now comes into play, the maximum weight of our caravan is now our GCM-GVM.  In the example we have been using, the vehicle now weighs 3540kg, the LC200 GCM limit is 6850kg (6850kg – 3540kg = 3310kg).  Therefore, the maximum weight of a caravan this vehicle can now tow is 3310kg.  In some cases, you may also be able to increase the GCM depending on your state or territory and the vehicle, these are things you will need to consider for your own personal situation.

I hope I have highlighted that its not as simple as saying my vehicle has a tow rating of 3500kg, I’m going to go out and buy a 3.5 tonne van.  The things that you should be considering are the GVM, GCM, the tow ball mass of your intended caravan, the kerb weight of the vehicle and its allowable payload, then consider your intended payload (family + accessories).  I know this all sounds overwhelming, and the truth is it is very
difficult to get correct, hopefully I have given enough information for you to make some more informed decisions.

Choosing your Caravan

I have shared some information on choosing a suitable tow vehicle, now I would like to share some advice in regards to caravan weights for you to consider when selecting a caravan.  It is my opinion that payload is a very important consideration when selecting a caravan.  All vans should come with a plate that will list the Tare Mass.  Tare Mass should be the weight of the caravan with its accessories fitted, in this scenario the Water tanks and gas bottles will be empty and when filled will eat into your payload.

To work out your payload you simply need to subtract the Tare Mass from the ATM limit.  Using our van as an example our Tare Mass is 2126kg the ATM limit is 2750kg (2750kg-2126kg=624kg), we therefore have a payload of 624kg.  Any accessories you add on like additional batteries and solar panels, diesel heaters etc are going to eat into your payload.  The other thing about tare mass is that it is measured with everything empty, i.e. your water tanks and your gas bottles.  We have 2 x 95l water tanks, and 2 x 8kg Gas bottles, if we subtract this from our payload (624kg – 206kg = 418kg), our payload is now only 418kg.  I can tell you that we find our payload of 418 kg very difficult to manage, we really have to compromise as to what we can have in our caravan. 

It is important that you have a close look at the payload of prospective caravans, I have come across many caravans with a payload of 400kg before you even consider water and gas.  For anything more that a short weekend away, it would be very difficult to be compliant with this payload.  So my advice when choosing a caravan is to pay carful attention to payload to ensure you get a caravan that is going to be suitable to your needs.

Loading your car and caravan

Where you load your payload into your car and caravan can have a significant impact on the overall performance of your combination.  In many cases simply re-distributing your load can be the difference between being compliant with limits or not. 

The most common issue we encounter on tow vehicles is an overweight rear axle (particularly in Ute setups).  When setting up a vehicle for touring its pretty common to load the boots and trays with a ton of gear that makes touring life more enjoyable.  The issue with this is the majority of the weight of these items end up on the rear axle.  On top of this we will be placing our caravan on the tow ball, at this point TBM is then transferred onto vehicle, but its not just the TBM, due to physics the amount of weight transferred onto our rear axle can be as much as 160% of the TBM.

For these reasons when setting up your towing vehicle it is best to position heavy items as far forward as possible.  In Ute trays, its best to try and position heavy items like fridges, batteries etc forward of the rear axle.  A trick I use personally is to take advantage of the storage that’s often located behind the rear seats.  This is where I tend to story heavy items like my bottle jack and recovery equipment.

For your caravan, you’re going to want to try and store heavy items down low and as close as possible to the axles.  You will also want to aim to distribute your weights as evenly as possible across the East to West axis of the van.  This is why you will often find on well manufactured vans that the batteries will be above the wheels on one side and the fridge and kitchen will be above the wheels on the other side.  There will often be 1 water tank forward of the axle and another behind the axle.   Good Manufacturers are trying to evenly distribute the weight following this principle.  Its now up to you to continue this, any heavy items should be stored down low and close to the axle, save your higher cupboards for light items like clothes and snacks.

Another important consideration when loading your van is controlling the TBM.  The ideal range for your TBM is between 8-10% (unless otherwise specified by the manufacturer).  For compliance only a maximum TBM is specified, so this is more of a guide rather than legislation.  Positioning too much weight forward in your caravan can lead to a heavy TBM, and as explained above this can lead issues with your tow vehicles axles weights.  To much weight to the rear of a caravan can lead a light TBM, it is this situation which can be the most dangerous.  Too much weight in the rear of the caravan can lead to something truckies refer to as “the death wobbles”.  This is when a caravan starts swaying left to right, and once it starts it can be very hard to recover and the consequences can be catastrophic.

Know your weights

Ignorance isn’t bliss, unfortunately the old Ausie adage of “she’ll be right mate” isn’t an approach you should adopt when it comes to caravan weights.  Not only can overweight setups impact performance and wear and tear, but there can be legal and insurance ramifications as well.

The issue of overweight caravans on the road is something that has been largely ignored in the past.  However, in the last few years, QLD launched a blitz weighing caravans as part of an education program, it was reported that 9 of 10 caravans were found to be overweight, however as this was an education program no fines were issued.  A subsequent blitz was completed in Maryborough QLD where 17 rigs were weighed, of those 12 were found to have issued and 5 fines were issued.  You should expect given the data that has been published that this trend will continue.

Perhaps the bigger reason to ensure you know your weights is for insurance purposes.  Most if not all insurance agencies will state in their PDS that they will not cover you if your vehicle / combination is found to be unroadworthy.  An overweight setup is no longer roadworthy, and if an insurer was to weigh your setup in relation to claim and if the combination is found to be overweight, you can expect the insurer to void your insurance cover.

To understand your caravan weights, you could visit a local public weighbridge.  With some fiddling around driving on and off and unhitching you could give yourself a reasonable ball park number for your GVM, ATM and GCM.  However, to really get accurate information on all of your caravan weights, I would recommend finding a specialised service provider.  At Svedos Weigh we will provide you with accurate values for your GVM, ATM, GTM, GCM, axle weights and tow ball mass.  Working with a specialised service provider like us will also allow you to assess your load distribution to ensure your TBM is in its ideal range, and receive expert advice on how any issues identified can be addressed.  It is most definitely a worthwhile investment.