Image

The modern touring caravan is a sophisticated home from home.

Loaded to the gunwales with all the equipment needed to make sure that the owners are protected and cossetted whatever the weather makes sure that very few models are what can be termed lightweight.

The trend with car manufacturers is to use lightweight materials wherever possible so as to make the vehicles as light, but consistent with strength, as possible.

Bearing all this in mind the caravanner has a difficult choice in finding out which towcar  will be heavy enough to tow his caravan.

This partly explains the enormous growth in the use of 4 x 4 vehicles used as towcars.  Other reasons are the many attributes of a four wheel drive.  Its ability to tow off a wet grass field, virtually impossible with front wheel drive, the higher driving position – it is really surprising how much more is visible by being those extra inches higher and the inherent feeling of safety that the 4 x 4 engenders.

To try to make a very grey area a little clearer we must run through the requirements of the match between tow vehicle and caravan.
 

Weight Matching

The 85% rule – this is not really a rule but a recommendation that has been arrived at after lengthy discussions between leading experts, the caravan clubs and the National Caravan Council.

This ‘rule’ states that the weight of the laden caravan should not exceed 85% of the kerbweight of the towing vehicle.

Laden weight of caravans is the weight of the caravan with all the goods and chattels ready for the road.  This figure must not exceed the MTPLM, This is Eurospeak for “Maximum Technical Permissible Laden Mass”.

Kerbweight of the tow vehicle is the weight of the empty car but with all fluids at their correct level and a full tank of fuel.
As an example, let’s take a laden caravan as weighting 1120kg.  To find out what weight of tow car you should have divide 1120kg by 85 and multiply the result by 100, this works out at 1318kg.  In this example therefore to stay within the rule a car such as Subaru Legacy or Ford Mondeo could safely tow our mythical caravan.

The weight of 4 x 4 vehicles which can be over 2000 kg ensures that virtually all caravans on the British Market can be towed easily and with rock steady stability.

The “rule” states that It is acceptable for an experienced driver to be able to tow up to 100% of his vehicles kerbweight.

Noseweight

The noseweight of a caravan is without doubt one of the most important things contributing to the safety and stability of the complete outfit.  It is also one of the least understood with experienced and beginners alike.
We will explain what noseweight is, how to measure it and most importantly what it should be.

The noseweight of a caravan is the force exerted in a downwards direction onto the towball of the towing vehicle when they are both stationary.

A caravan is far more sensitive to noseweight than a normal trailer because of its ‘slab sides’ which act like a sail and can cause swaying in a wind.  These winds can cause a badly loaded caravan having an incorrect noseweight and a towcar that is too light to go out of control and turn over.  The most common cause of these sidewinds is the ‘bow wave’ of a fast overtaking coach or lorry.

Some caravan handbooks state an ‘ex works’ noseweight.  This is fairly useless and to all intents and purposes can be ignored as the important noseweight is the laden one.  This is the noseweight when the caravan is loaded ready for the road and this weight can be adjusted to a certain extent by moving objects backwards or forwards inside the caravan.

How do we measure noseweight?

The accurate measurement of noseweight is of vital importance to the stability of the outfit and the safety of our families, and ideally it should be measured before each journey.
Noseweight is measured on level ground with the caravan also in a level position loaded ready for our holiday or weekend.  A noseweight indicator, which can be purchased at most accessory shops, is placed under the hitch and down to the ground, the corner steadies are wound up and the weight of the hitch is shown on the indicator by winding up the jockey wheel.  The resultant reading can be read off the indicator’s scale.

As a cheaper but just as accurate alternative a pair of bathroom scales and a piece of broom handle can be used.

In either case the reading can be adjusted by moving items about inside the caravan-don’t forget to wind the steadies down before getting back in the caravan however.


What should the noseweight be?

The National Caravan council sets a guideline of seven per cent of the loaded caravan’s weight.  This can only be a guideline because in a great many cases this would exceed the weight allowed by the vehicle manufacturer on the towball of their car.

The starting point in setting the noseweight is to look in the vehicle’s handbook, the section ‘technical data’ is where the allowed noseweight of the vehicle will be found.  It is this figure that must not be exceeded and it will be this figure that the police will go by in their increasing number of roadside checks.

So for the best stability the caravan’s noseweight should be as heavy as it can be within the confines of the car makers allowance.

 So you buy a 4 x 4 with an enormous allowance on the towbar, QED, not quite, the allowance of the caravan chassis manufacturer comes in here.  The brake overrun device on the ‘A’ frame of the caravan can be damaged or become ineffective if the caravan chassis manufacturer’s figures are exceeded.  Oh dear, it all seems so complicated!

The major chassis maker Al-Ko Kober sets two limits on its towbars, 75 kg and 100 kg.  If in doubt a call to them would establish your limit.

The discussion so far only refers to stationary outfits.  What happens when they are on the move?  Very little research has been carried out covering this subject but in general the faster the speed, the lighter the noseweight, and this explains why outfits start to become unstable at higher speeds.

Under braking, the noseweight increases dramatically, going uphill or accelerating it will decrease significantly.

To a certain extent the shape of the caravan has an influence on this, the more old fashioned the shape the larger effect speed has on the decrease of noseweight, and the more steamlined the smaller effect speed has.

Manual or Automatic?

Towing with an automatic gearbox offers several advantages over manual gearboxes, the main one is that the vehicle is always in the right gear.  So many drivers never seem to know which gear that they are in or even should be in.  This is where the automatic box comes into its own.

Automatic gearboxes are also far more gentle on the drive train of the car and on the caravan in general.

Automatic vehicles will creep along slowly and are remarkably good at hill starts. Their disadvantages are a very slight increase in fuel consumption and the generation of more heat than manual boxes.  It is this latter point that causes problems if there are to be any.

For serious towing, long distances in hot weather or in mountainous regions a gearbox oil cooler is absolutely essential.  Most automatic cars will have a transmission oil cooler fitted as standard but an additional one might well be necessary. A serious discussion with the technical department will be in order here.

It is very important that you have not been put off by our little dissertation, none of this is complicated if you give it some thought, your safety might depend on it.

Adrian H French

 

 « go back