Words and Images by: Collyn Rivers N8054

The cult of what Bill Gates calls ‘biggerism’ is seemingly escalating in the RV field, generally speaking. Some manufacturers are adopting new materials and saner design, but many attempt to produce virtual home units on wheels, yet maintain their mantra that strength requires weight.

One unfortunate result is that the delivered weight of some RVs turns out to be much higher than expected, leaving little over for anything that is added by owners.

Insurers and police are aware of this. The former may disallow claims if a vehicle is found to be grossly overweight, the latter may take even sterner action.

In the determination of this weight, there are some major differences between caravans (a fifth wheeler is legally a caravan) and campervans and motorhomes.

Defining the weight

The so-called Tare Mass of a caravan includes the weight of factory supplied  water tanks and gas bottles - but not of the water and gas.

There is no obligatory Personal Effects Allowance for caravans (including fifth wheel caravans) but there is an industry ‘recommendation’ that single axled caravans under 1500 kg will have 250 kg, twin axled caravans 300 kg and twin axled biggies will have 400 kg.

Bearing in mind that 100 litres of water weighs 100 kg, some RVs carry over 200 litres and have substantial tankage for grey water (dirty stuff) and black water (filthy stuff), and that gas weighs 9 kg per bottle, much of that allowance is illusory.

Campervans and motorhomes have a vaguely similar system except that a small part is legally enforceable.

The Dept of Infrastructure and Transport’s Circular 0-4-12. ‘Certification of Campervan and Motorhomes’ (issue 4, June 2005) requires water tanks to be full, and the fuel tank to contain 10 litres. There is an obligatory Personal Allowance of 60 kg per person for the first two people, and 20 kg per person thereafter.

To quote The Campervan and Motorhome Book, ‘an RV’s permissible weight (Gross Vehicle Mass) includes everything in it: toilet, fridge, shower, gas bottles, water, plus driver and passengers.

If exceeded, the vehicle may not legally stand on a public road, let alone be driven on one’. This can (and on one known occasion did) result in a motorhome in a dealer’s showroom being not drivable on road, as the showroom weight less driver, let alone passenger/s, was its GVM.

A caravan’s weight rating is complex. The Gross Trailer Mass (GTM) is the total carried by its tyres, carrying the maximum permitted load when coupled to the tow vehicle.

It is whatever is the least of the wheels/tyres/suspension/axle ratings recommended by the associated manufacturers.

The Aggregate Trailer Mass (ATM) is the total permissible mass when carrying the recommended maximum  load – including the mass imposed on the tow vehicle.

Must be hard to find a park that will accept this monster US fifth wheeler. Pic: courtesy www.dieselpowermag.com  

Tare Mass in practice

According to its 2013 Owners Handbook, Recreational Vehicle Manufacturing Australia (RVMA) members ‘are required to weigh each product as it leaves the factory and to have the tare mass stamped on the Consumer Information Plate which is affixed to the vehicle.’

This, however, can trap first time buyers because, ‘items fitted to the caravan after it leaves the manufacturer’s factory are not considered part of the tare mass’.

It is not widely realised that many RV makers produce standard base products and all ‘optional extras’, even if included when placing the order, are supplied and fitted by the supplying dealer.

These may include extra gas cylinders, extra spare wheel,  batteries, solar, generators, air conditioning, microwave oven, TV, washing machine, awning and alternative spring mattresses etc.

None of the above is included in that ex-factory Tare Mass, nor necessarily made known to the buyer.

That weight does, however, form part of the maximum legally permissible on-road weight.

The result can well be (for a caravan or fifth wheeler at least) a product that has no allowance left over for personal effects.

Campervan and motorhome buyers, legally, are marginally better off in that the Personal Allowance is inviolate. It has to be there.

None of this really matters if the obligatory or ‘recommended allowance’ were realistic.

But even before taking the bikes, boats, outboard motors etc: the reality for two people touring for any length of time is unlikely to be less than 300 kg or so.

I do not suggest that all this is needed. My wife and I eventually travelled with far less, but years of observation shows that most people do carry a fair load.

I strongly advise anyone buying a costly RV to specify in writing, the spare capacity of that RV ex dealer. Further, to not accept delivery until that RV is weighed in your presence on a certified weighbridge.

Category: Advice
Written: Thu 31 Oct 2013
Printed: November, 2013
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