Updated 16 March 2016
The maximum caravan weight safe to tow has no simple answer. This article by Collyn Rivers explains why – and how to know what it is.
Historically, the caravan weight safe to tow was taken to be any that weighed the same or less than the towing vehicle. But this was at a time when most caravans were 3.5-4 metres long, weighed 900-1200 kg on road, and rarely towed above 80 km/h. Where that length and weight still applies, as with light (sanely laden) camper trailers that trailer/tow vehicle weight is still fine.
The maximum caravan weight safe to tow becomes more complex with caravans that are longer than 4 metres. With these the limiting weight is very much a function of where weight is distributed along the caravan’s length.
Caravan weight safe to tow
Here’s how to feel for yourself why this matters.
Hang any suitable bar (a broom handle will do at a pinch) by a rope. Add a couple of weights as shown below.
This is a simplified model of a caravan with the weight close to the centre. If you hold the bar and turn it as if it were a caravan swaying you will find that, even with heavy weights, it can be turned and stopped with ease. Pic: caravanandmotorhomebooks.com
But try it now with the weights like this:
This is a simplified model of an end heavy caravan (of exactly the same weight). Hold and turn it as before and you will find it surprisingly hard to start and stop. Pic: caravanandmotorhomebooks.com
You will also find the lighter the person doing the turning, (or the tow vehicle controlling the caravan) the harder it is to stop and start it moving. Why this happens is all to do with what engineers call ‘Moments along a Beam’. This too is readily demonstrated.
As shown by a see-saw the ‘effect’ of weight on a pivoted beam (e.g. a caravan chassis) is related to its distance from the pivot (axle). Pic: original source unknown.
What this means in terms of caravan weight safe to tow is that a short heavy van is safer to tow than a long van of the same weight (unless much of the weight is centralised). The see-saw effect also shows that is not a good idea to have anything heavy (such as a tool box, batteries, spare wheels or a bicycle rack at the rear of any caravan – especially a long one.
Owners have some control over this – the heavier whatever you load, the closer it needs to be in front of and behind the axles. Do not for moment load heavy stuff way up front and ‘balance’ that heavy stuff way back.
There are too many variables too give any but a general guide of the caravan weight safe to tow, but a long end-heavy ‘van needs a much heavier tow vehicle than a centre-heavy ‘van of the same length. Some locally made ‘vans are (in my opinion) now far too long and end-heavy to be towed safely by any vehicle short of the big Ford 250s etc.
Caravan weight safe to tow
I would have no problem towing a correctly laden 3.5 metre caravan of the same laden weight as the laden tow vehicle, but were that to be a typical 6 to 6.5 metre end-heavy local product I would only tow it with a vehicle at least 30% heavier.
If seeking a caravan longer than 7 metres I seriously advise readers to consider the dynamically more stable fifth-wheel caravan format.
For a warning and explanation of why many caravans are overweight see http://caravanandmotorhomebooks.com/caravan-tare-weight-issues/
For a more technical explanation see http://caravanandmotorhomebooks.com/caravan-and-tow-vehicle-dynamics/
For information on tow ball mass see: http://caravanandmotorhomebooks.com/caravan-nose-weight/
See also http://caravanandmotorhomebooks.com/making-caravans-stable, also http://caravanandmotorhomebooks.com/reducing-caravan-sway. For info on fifth-wheelers see http://caravanandmotorhomebooks.com/fifth-wheel-caravans-safer/
If you found ‘caravan weight safe to tow’ helpful you are likely to find my books even more so. They include the Camper Trailer Book, Caravan & Motorhome Electrics, Solar That Really Works for RVs), Solar Success (for home and property systems), and the all new Caravan & Motorhome Book. For information about the author – Bio.
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