Caravanning Now - What's the correct height for my Tow ball?
The Caravan club handbook and EC Directive 94/20/EC.
Both the Caravan club (handbook page 640 - 1999/2000
edition) and EC Directive 94/20/EC say that the coupling ball is 50
mm diameter and when measured from ground to ball centre should be
between 350 and 420 mm (vehicle laden).
This gives nearly 70mm (nearly 3 inches) of latitude in height.
NOTE: Laden is not specified what Laden means.
Is this fully laden as per vehicle manufactures definition or with
the passengers (at 68.5 kg per passenger) and 6.5 kg of luggage per
passenger.
See also the Witter
Trade article here (at time of writing) which states (and I quote):
" What height should the towball be?
The million Euro question! The EC Directive 94/20/EC states that the
towball height should be between 350 and 420mm with the vehicle in
the ‘laden’ condition. Laden condition may have been defined (by the
manufacturer) as either fully laden (the maximum technically permitted
mass of the vehicle as shown in the vehicle handbook), or, conventionally
laden (defined as 68.5kg per specified passenger seat and 6.5kg of
luggage per specified passenger and located in the centre of the luggage
storage area). Alternatively, the towball may be at the height or
height range specified by the vehicle manufacturer in the homologation
documents and possibly the vehicle handbook. Not so straightforward!"
NOTE 2: If the car is actually at its fully laden weight (GVW) then you would exceed the GVW by the weight of the down force on the tow ball. (Thanks to Lutz Schelisch for pointing this out.)
NOTE 3: It's actually far more complicated.
You have to take max axle weight into account and also the overhang
length.
For Example: A 75kg caravan nose weight on a 110 LandRover puts around
125kg on the back axle.
Since most cars carry most of their luggage behind the rear axle,
it's pretty easy to exceed the rear axle max weight and remain in
the gross vehicle weight.
75kg on a 110's tow bar actually takes ~50kg off the front axle.
Luggage behind the back axle also transfers weight from the front
axle to the back axle, exacerbating the problem.
See also the page on what weight caravan you can tow
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