which caravan?

If the ATM is 1700kg, the GTM of 1550 kg and Tare Mass of 1300kg - does that mean that you can load up a max of 400k or only 150 kg. What does the axle load capacity of 1600kg mean?
You seem to know what you are talking about Ian...thanks
shameem

Hi Shameem,

Thanks for the compliment.

The Tare of 1300kg should be the dead-empty weight of the van as it left the factory gates - without gas in the bottle, water in the tank(s) or any post-factory (read: dealer fitted) accessories.

GTM (Gross Trailer Mass) is the maximum weight allowed to be supported by the wheels and axles of the trailer/caravan. That is, it is the total maximum weight (ATM) less the weight on the tow ball.

ATM (Aggregate Trailer Mass) is the maximum overall weight of the van - the weight on the axles plus the weight on the tow ball.

So, if this particular van actually has an empty weight of 1300 kg (that is the dead-empty weight on the axle(s) plus the dead-empty weight on the ball), you can quite legally put 400kg of gas, water and belongings in it, PROVIDED that when it's fully loaded the total weight is no more than 1700kg AND the weight on the axle(s) is no more than 1550kg. Therefore, if the total weight WAS 1700kg, there would have to be NO MORE than 1550kg on the axle(s) and AT LEAST 150kg on the tow ball.

[A different but related issue is that with a ball weight of more than 140kg, you should be using a 250kg weight distribution hitch. None of the round bar systems, either 2 or 4-bar, are rated for a ball load of more than 140kg.]

There is one other common figure on caravan spec. plates - maximum axle group rating. This is usually quite a lot higher than the GTM/ATM figures but is not a particularly usable figure. It refers to the strength and load capacity of the axle, hubs and bearings. For typical axles using 14" wheels, each axle can support 1450kg (with Ford 'slimline' bearings), so a tandem axle van with two of these axles, the axle group rating will be 2900kg. For 'off road' vans with 15" or 16" wheels running on 4WD type hubs with parallel bearings (usually Toyota, Nissan or Land Rover types), the axle group rating could be quite a lot higher.

But it is very unlikely the chassis manufacturer (who usually sets the GTM) or the caravan builder (who usually measures the Tare and sets the ATM will rate their construction anywhere near the maximum axle group rating.

Your example seems a little unusual for a couple of reasons: Firstly the 'axle load capacity' of 1600kg suggests a stronger axle/hub/bearing design than the typical 14" wheel type - perhaps one with 4WD-type hubs? But it also suggests we're looking at a single axle van.

The difference between Tare and ATM (the "payload") is 400kg. The de facto industry 'standard' is typically a payload (ATM minus Tare) of 300kg for single axle vans and 400kg for tandem axle vans - but there's no strict reason why this must be so. So a 400kg payload for a single axle van seems to suggest we are looking at a single axle van with strong 4WD type axle/hubs and perhaps built by an up-market builder who constructed the van to handle a larger than average payload. Am I close?

Ian...mate you are good!!
Just got a 2003 Olympic 2000 Series yesterday. With all the paperwork was all the details. It is a single axle. Wheel rim size/profile = 14 x 6; tyre size = 195 x 14, tyre pressure 320 kPa and all the previous information provided. Looks like a heavy duty setup (to the eye of someone with no experience). The weight distribution hitch "features the cam lock adjustable ball mount available in 250kg and 350kg hitch weights." It has two square bars and some pretty heavy duty chains (Hayman Reese). Who are you...what else can you tell me.
Regards
shameem

Hi Shameem,

Thanks again for the kind words - but don't get too carried away. We've picked up a bit in 5 /12 years living in and travelling extensively in caravans. [Please see About Us on our website for more details.]

But it's mostly stuff we've learned by reading the advice of REAL experts like Tom Olthoff. Tom was the technical writer for Caravan World magazine until they, in their infinite wisdom, dispensed with his services early this year - for very dubious reasons...

Malcolm Street's article on this site here has lots of good info, as do some of the other articles in the "Caravanning" section.

Your Hayman-Reese weight distribution hitch is excellent equipment, but must be set-up correctly to work properly. I'm frequently amazed at the number of caravanners with quality WD hitches which are doing next to nothing to level or stabilise the rig because of poor set-up. (Including many who say "But that's how the dealer set it up!")

Did you get the original H-R hitch instruction with the van and hitch? If not, I suggest you phone/email H-R to get a copy. Failing that, please feel free to email me for some tips on set-up. [Might even write it up into an article if there's enough interest.]

Ian

Thanks Ian,
I googled Tom Olthoff and lots of links come up. I might start of new track and ask the question again in a few weeks to flash out the issue sthat come up. This might provide you with more incentive to do a writeup on hitch & tow iisues.

I love your website.
Regards
shameem

Fine advice