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Why are caravan weights and masses so confusing?

Article by · 9 January 2018 ·

Caravan masses and towing weights are two of the most confusing aspects of caravanning – and it’s not hard to see why. To ensure you stay legal when towing, you really need to know a lot of data, and only some of it isn’t actually what’s advertised on your compliance plate or in a sales brochure.

Aggregate Trailer Mass (ATM), for example, is completely irrelevant to your towing limitations, as it’s not an offence to tow a trailer with a higher specified aggregate trailer mass than the maximum braked towing capacity of your car. It’s only an offence to tow a trailer that actually weighs more than the braked towing capacity of your car. For example, you can tow a trailer with an AGM of 3.5 tonnes behind an Isuzu MU-X provided the trailer physically weighs less than three tones.

Other weight listings can be just as confusing. Take the trailer’s axle group loading, for example. In some cases, the axle or axles aren’t rated high enough to carry the full aggregate mass of the caravan themselves (the Coromal Appeal AP554S is one example – its axle loading is 1718kg, while the ATM is 1939kg). The caravan is relying on a certain amount of ball weight to bridge that gap, which means that you can only legally tow the van if the ball is loaded to a certain point (in this case, 202kg at ATM). You’ve either got to sacrifice load capacity (effectively reducing the ATM) or ensure your tow car can legally have that much weight on the ball.caravan weights atm gvm gcm

The most confusing towing weights dilemma of all is the relationship between Gross Combination Mass, tow ball download, trailer mass and Gross Vehicle Mass. Here’s the scenario – you own a Toyota Fortuner which has a kerb mass of 2120kg and a load capacity of 630kg which equals a 2750kg GVM. You’ve filled it to the brim for a trip. It’s an auto, so you are towing a caravan that weighs 2800kg with 300kg of that on the ball. The Fortuner has a gross combination mass of 5545kg. Even in this situation, you’re 5kg overloaded, because although the car can legally tow 2800kg, the two cant ever weigh more than 5545kg. 2750 + 2800 = 5550.

Gross Combination Mass is the maximum specified weight that the car and its load and its trailer can weigh. In reference to caravanning, you’d make sure you were under this limit simply by adding the actual towed weight of your caravan (not the ATM – that’s largely irrelevant), the actual kerb weight of your car, and the actual weight of your load, which includes people and personal effects. Simple enough. In the above situation, if you lose 5kg from the caravan (empty the water tanks a little), you’re set.

In practice, though, the tow ball download stuffs up the simple maths. Because once you drop the tow-hitch onto the car’s tow-ball, that’s taken mass from the caravan and transferred it as load to the car. It hasn’t changed the Gross Combination Mass – that’s still the sum of the caravan’s weight, kerb weight and load weight – but you have just overloaded the Fortuner by 300kg, thanks to the ball weight.towing weights tow ball download

What you have to do now is find 300kg of savings from somewhere – either in the ball weight (you could probably afford to find some there – maybe 50kg by redistributing the load in the van, but lowering the ball weight too much will likely lead to trailer instability) or in the car. But most of it has to be from the car. Even if you take 300kg out of the caravan (thereby giving yourself a spare 300kg in the GCM), the car is still overloaded as long as the ball-weight is more than 0kg, and that just can’t happen. It’s a balancing act.

Essentially, in a vehicle where the GCM is simply an addition of the GVM and maximum braked towing capacity, you could never responsibly or legally tow a caravan of that weight while your car is loaded to its own GVM.

None of this is to say ATM isn’t important, it is! Like GVM, which is the most a vehicle is permitted to weigh while being driven, Aggregate Trailer Mass is the most a caravan, camper trailer, box-, car- or horse-trailer is able to weigh while being towed, and is a mass that’s measured irrespective of the tow ball download. You can’t load up the ball to reduce ATM and if your aggregate trailer mass is more than what your car can tow, you are effectively reducing the potential load-capacity of your caravan.

No wonder towing weights are all so confusing, huh?

To make it all make sense, use our Car and Caravan Weight Calculator to make sure you’re not overweight, or to check the caravan and car combination you want to use are compatible.

If you’ve got a specific question about your own towing masses, weight distribution, limits or loads ask it in the comments below and we’ll answer, or find answers to your questions. The information will help out other caravanners confused by it all.

mm

About Time To Roam

Australia's premier magazine focused on the people and culture of caravanning and camping.

27 Comments

  • comment-avatar

    Another important weight is the Tare. There has been significant misunderstanding around the legal definition and how it is applied. It is important because Tare is used to calculate your maximum payload.

    The legal definition of Tare in VSB-1 is:
    “Tare Mass is the total mass of the trailer when not carrying any load, but when ready for service, unoccupied (if relevant) and with all fluid reservoirs (if fitted) filled to nominal capacity except for fuel, which shall be 10 litres only, and with all standard equipment and any options fitted. This includes any mass imposed onto the drawing vehicle when the combination vehicle is resting on a horizontal supporting plane. (Fluid reservoirs do not include water tanks and waste water tanks fitted to caravans).”

    The key points here are that Tare is measured at the point that the caravan/trailer is ‘ready for service’ i.e. the point of registration. Not at the factory unless it is being supplied directly from the factory to the customer.

    It must include ALL standard equipment i.e. what is advertised in the brochure.

    It must include ALL options i.e. what you included in your contract and paid for as options such as solar panels, extra batteries, awning, extra spare wheel, bike racks etc.

    For a great explanation of ALL the ratings and masses, go here:
    http://docs.wixstatic.com/ugd/74afe1_b5e04665a68442208d9142a2a77b479e.pdf

  • comment-avatar

    David

    Thank you for confirming what I already knew. ” It’s only an offence to tow a trailer that ACTUALLY weighs more than the braked towing capacity of your car”. At the caravan show today I had two salespeople swear that the ATM of the caravan, irrespective of the actual weight of the caravan as towed, could not be greater than the towing capacity of the tow vehicle. I have a 2000kg towing capacity, the caravan I want has a tare of 1740kg and an ATM of 2120kg. I argued that if I loaded the van to a total weight of 1999kg then I could legally tow the caravan. They said I could not and would not sell me a caravan. Both of these poor imbeciles missed out on a $70,000 caravan sale.

  • comment-avatar

    Ralph

    I have a Subaru 2008 tribeca with gvm 2000kg and towball weight 160kg can i tow a caravan with gvm 1600 tare1420 towball 140

    • comment-avatar

      Sean

      Yes. I think you’ll find that the Tribeca has a braked towing capacity of 2000kg and a GVM of 2586kg. Add those two together and you get your GCM of 4586kg. The van is under the cars towing/towball limits being 1600kg/140kg. This leaves you with available payload of around 400kg. Keep in mind as soon as you load the van you could potentially go over the cars towball limits.

  • comment-avatar

    noel wheeler

    I have a 2007 Navara rx manual and tow a 1999 Jayco westport van. Usually with 2 mountain bikes on the A frame and 2 15ft kayaks on the roof rack of the Navara and fridge genny and assorted junk in the back. how do I weigh it on a weighbride as a single unit? or weight car and van seperately? I have never worried before as it tows OK.

  • comment-avatar

    Tony

    I have a 2007 Coromal 618 Lifestyle Tare 1661 GTM 2003 ATM 2140 Fully loaded water & Gas Etc. Van weight unhooked 2200 Ball Weight 160 hooked up to a Toyota Landcruiser (Troopy) GVM 3035 when weighed was 2040 which ment I was 60K over on the Van but they tell me I can take the 160 ball weight off the Van giving me an extra 100k to put in the Van providing I don’t exceed the car wieght of 3035 is that correct

    • comment-avatar

      Sean

      Towing capacity of 3500kg Tony? Your Gross Combination Mass (GVM) will then be 6535kg. If you add your current weights Troopy – 2040 (I would assume your kerb weight is a lot higher??) and Coromal 2200kg your combined weight is only 4240kg. Well under.

  • comment-avatar

    Bill

    We have a ford ranger XLT that can tow 3.5 ton. We pull a Jayco Silverline with a GVM of 2889, a TARE of 2579 and a towball weight of 220kgs. When van was weighed fully loaded with gas, water, food and everything we were taking, disconnected from Ute & on jockey wheel it weighed 3006 kg. We were told we were 117kgs overweight. Should the towball weight have been taken into consideration.

  • comment-avatar

    WARWICK

    just clarifying towing rates, 2010 dmax 2WD GVM 2900 GROSS COMBINATION WEIGHT RATING (BRAKED) 5300 MAX AXLE REAR 1680 TOWING A Coromal 605 LIFESTYLE Caravan ATM 2010 GTM 1900 TARE MASS 1592 AXEL GROUP LOAD CAPACITY 2600. IS THIS OVER/UNDER ALLOWABLE REGULATIONS? I NEED HELP IN UNDERSTANDING ALL THESE NUMBERS.

  • comment-avatar

    Martin

    If my van is loaded to its capacity, 3.5T and I have a tow ball weight of 300kg, essentially 300kg being transferred as load to the car, can I then add another 300kg to the van ? If not, how can I ever reach my legal GCM ?

  • comment-avatar

    Geoff Connelly

    I would appreciate confirmation, or corrections, to my calculations, based on your advice:
    1. My tug is a 2005 Land Cruiser (4.2 TD Auto.) The unladen (tare) is 2,500kg and GVM is 3,260kg. So, I can add 760kg of weight. If we assume 2 adults and 2 fuel tanks is 260kg that leaves me with 500kg of additional gear – in the back and on the roof rack, etc.
    Once I hook up the van, with 215kg on the ball, my available weight (for luggage) is now 285kg – is that correct?
    And, the car is legal to tow 3,500kg.
    2. The van I’m buying is a 2018 Lotus Trooper (20.6’). Tare weight is 2,845kg and ATM is 3,495kg. This means I can add, up to, 650kg incl. the weight of the (after market) stability control system, the water in the tanks, bbq, food, tools etc.
    If I’m right, a (20kg) generator may not find its way into the genie slide built into the van!
    Thanks for a great site. Geoff.

  • comment-avatar

    Bruce

    I have a Pajero Sport with tow capacity 3100, GVM actual is 2320 (max is 2710) and ball weight with van is 302 (max 310).
    My caravan is ATM 2923 and GTM 2621. Recommended GCM is 5400 and current is 5240. Does this calculate ok for me to be compliant?

    • mm

      Brendan Batty

      Sounds like it – all the numbers are below the limits stated by the manufacturer. How are the rear springs with that much weight on it – or have you had the upgraded?

  • comment-avatar

    Bruce Swaffer

    HI I have a cell peninsula caravan atm is 3200kg gtm is 2890 tare mass is 2834kg and axle group load capacity is 3500kg ????? the tow vehicle is a lexus wagon lx570 towing capacity 3500kg towball download 350 kg ????? many questions how much water food clothing is allowed in the van and or what can be put in the vehicle ie people etc etc this is bloody confusing to say the least your help would be appreciated thanks.

    • mm

      Brendan Batty

      Hi Bruce, if the numbers you quoted are correct, you can travel with 366kg of load in the caravan, made up of water, clothes, stuff you need to use like kitchenware etc.

  • comment-avatar

    Ken

    Hi, I have a 2005 Pajero 3.2did with a tow capacity of 2500, 250 max ball weight, kerb mass 2240, GVM 2810, GCM 5310.
    I am looking at purchasing a Coromal caravan which from the spec plate has the following…..GTM 2459, TM 1970, ATM ..??, ball load at Tare 133, axle group rating 2951,max permissible ball load 259.

    Will I be compliant to tow this van?

    Will

  • comment-avatar

    Darryl P Goodwin

    Hi….my GCM is 5750. and my car and van hitched weighed 5140…
    towball 220
    so from what i can work out i still can put 390kg in van and car

  • comment-avatar

    Burrell Glasspell

    I have an Isuzu MUX and looking at buying a caravan with a Tare 2318 and GTM 2631.
    I am totally confused re all of the weight stuff and hoping someone can tell me that the above combination works

  • comment-avatar

    Leisa

    Hi,
    Purchased a volkswagen Amarok ultimate earlier this year.
    Ordered a 23 ft caravan with a atm of 3300 & ball weight 330kg.
    Was told by salespeople the Amarok would be no problem.
    Pick up the van in 2 weeks. Have just discovered with a lot of research that it will not be fine.
    Now looking at the new Nissan Patrol or Ram.
    Would prefer the patrol.
    GCM is 7000kg
    GVM is 3500kg
    Towball Download 350kg
    Payload is 750kg
    Kerb weight is 2800kg with full tank of fuel and 1 x 70kg person included

    Can you please tell me if this will be legal.
    All I care about it being covered by insurance.
    Used your calculator last night , but there seems to be a problem with it now.
    Thanks,Leisa

    • mm

      Brendan Batty

      Hi Leisa, yes, unfortunately you’ve been given bad advice on the Amarok – it can only tow 3000kg. The Nissan Patrol might be able to handle it. The RAM 2500 definitely will. The image below are the results from the calculator if you bought the Patrol and loaded everything to its maximum. Note, the GVM will be exceeded, so you’ll have to account 330kg for ball weight and take that weight out of your car.
      Caravan Calculator
      However, that ball weight is concerning, as if it’s already that heavy without anything in the caravan, it will only get heavier when you load things into it. As the Nissan has a sliding scale on ball-weight capacity (the more load in the car, the less ball weight you’re allowed), you might find it’s just on the edge of it’s ability. If the sales people told you your car (Amarok) will be suitable, you might have grounds to cancel the sale. Can you email me more details? editor@timetoroam.com.au.

  • comment-avatar

    Ian

    Is your calculator working correctly ?

  • comment-avatar

    Isn

    Is your calculator working correctly. Your GCM figure does not seem to minus the tow ball weight from the ATM when calculating the weight of the towing vehicle.

  • comment-avatar

    Grace

    I have a caravan with Tate 950 , I drive a v8 Holden wagon , my tow ball is 1600kg can I tow this van .. do i need heavy-duty suspension

  • comment-avatar

    Leslie

    I have a New Age MR16ES2. Compliance is listed as : Tare – 2030. ATM – 2340. GTM – 2200. I took this over a weighbridge on the way back from a trip and discovered Gross Combination Weight – 4780 and Caravan alone – 2560. I would still like to load two bicycles. I tow with a VW Touareg diesel rated: Towball – 280, Kerb Weight – 2185, Gross Vehicle Rating – 2880, Gross Combination – 6390.
    Is this OK?

  • comment-avatar

    Kevin

    We have a 20′ Newage OzClassic Slider in WA: ATM 3140, GTM 2970, Towball 170 Tare 2740 and an Axle Group Loading of 3200. Not surprisingly with 205lt of water and all the other bits and pieces we are overweight.
    I tried to get the ATM upgraded by first getting the brake check and was told that we need to upgrade from 10″ to 12″ brakes.
    From the research which i have done it seems that the GTM can be increased to the lowest rated component ie brakes/springs/coupling.
    If that is the case i should be able to increase the GTM to 3200 and therefore increase the ATM to 3370.
    Would this be correct??
    They are the standard Alko 10″ electric brakes with 16″ rims (Factory fitted).

  • comment-avatar

    Brenton

    Hello i have a 2016 Hyundai Tucson xtreme, it is apparently towing capacity 1600 kg what weight caravan can I tow.

  • comment-avatar

    Geoff

    My caravan (Jurgens Skygazer) has an ATM of 1800kg. In it’s current configuration there is 1560kg load on the axle and 180kg on the tow ball.

    Clearly 1560kg is part of the ATM. Does the tow ball down weight also count? If it does the weight is 1740kg leaving only 60kg for additional gear. If it doesn’t then I have a much more respectable 240kg available.

    I do not want to load up to the ATM but I do want to carry at least 60kg for bikes and bike gear.

    Hope you can clear this up for me.

    Thanks…..Geoff


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