The pressure that a tourer's coupling exerts on the car's towball is called 'noseweight', and it's crucial to outfit stability. If it's too low, a van may be unstable, but too heavy and the towcar's handling will be impeded.
Caravans are designed with the axles at the optimum distance from the coupling, taking into account the cooker, fridge, toilet, and other built-in equipment but a mnaufacturer cannot control how the owner will load the van and it's this which is most likely to affect noseweight. Storing light items in the roof lockers, medium weight items under the bunks and heavy items over the axle or forward of it will maximise stability but it's vital to ensure the noseweight is correct before setting off.
Working out an appropriate noseweight values requires a bit of detective work. For the caravan, the chassis manufacturer stamps both the maximum noseweight and the maximum load that the coupling is designed to carry on the coupling itself, designated 'S' and 'GA', respectively. For your towcar, the owner's manual will list the vehicle's maximum noseweight. Since 1998, towbar manufacturers must state a maximum noseweight on the towbar plate. When loading, work to the lowest of these figures. Using them, you can experiment until you find the loading which gives you the optimum stability.
There is also evidence that the noseweight should be around 7% of the tourer's MTPLM. A van with an MTPLM of 1200kg ought to have a noseweight of 84kg. Remember, however, that the noseweight figures from the chassis, tow vehicle and towbar manufacturers take precedence. Exceeding the lowest noseweight could invalidate your warranties in the event of an accident, and put you at risk of breaking the law.
Gauging noseweight
There are two ways to check a caravan's noseweight but both require the caravan to be on level ground, with the corner steadies so the caravan is on its road wheels and the jockey wheel. You can then use either a noseweight gauge
– available in caravan accessory shops for around £30 – or bathroom scales, plus a piece of wood to spread the load on the scales, and a 14-16.5in length of broom handle.
Whichever method you use, wind down the jockey wheel until the noseweight gauge or the broom handle can be fitted into the head of the coupling. Once the weight of the nose is supported, the jockey wheel can be raised off the floor and weight recorded from the scales or gauge, depending on what you are using.
AL-KO's Premium Jockey Wheel has a built-in gauge for calculating noseweight. For the best effect, it does require some work the first time it is used. It entails measuring the distances from the centres of the coupling head and the jockey wheel to the centre of the road wheel in centimetres. Then use
this formula:
R = Maximum noseweight allowed for this van/towcar combination.
S = Smallest of four possible weight limits, such as of the towbar, the caravan drawbar, the ball coupling, or the over-run device. (The information, which should be found in the handbooks, is likely to be 75-100kg.)
LS = Distance from the centre of the coupling head to the centre
of the caravan road wheel.
LR = Distance from the centre of the jockey wheel to the centre
of the caravan road wheel.
In the case of a twin-axle van, the LS and LR distances are to the mid-point between the road wheels.
Once you have established the maximum load, mark the jockey wheel gauge with a permanent marker, so the same calculations aren't needed every time you load the caravan.
All three methods are helpful for assuring stable towing, be aware that any reading you get is approximate and best used as
a guide.
Adjusting the weight
Getting a correct noseweight is normally a matter of adjusting the loading. If the reading is, say, less than 50kg, move items loaded in the van forward of the axle line to increase the noseweight. If it is too heavy, move them back, but not more than 2ft behind the axle line. If that doesn't fix it, move items into the towcar or leave them at home.
Other factors such as passing HGVs, cross winds and tyre pressure affect stability but getting the highest noseweight possible within the various limits will go a long way to minimise these and make towing safer.
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