Opel 2015 Combo Owner's Manual page 128

126 Driving and operating
The permissible trailer loads are
specified in the vehicle documents. In
general, they are valid for gradients
up to max. 12 %.
The permitted trailer load applies up
to the specified incline and up to an
altitude of 1000 metres above sea
level. Since engine power decreases
as altitude increases due to the air
becoming thinner, therefore reducing
climbing ability, the permissible gross
train weight also decreases by 10 %
for every 1000 metres of additional
altitude. The gross train weight does
not have to be reduced when driving
on roads with slight inclines (less than
8 %, e.g. motorways).
The permissible gross train weight
must not be exceeded. This weight is
specified on the identification plate
3 165.
Vertical coupling load
The vertical coupling load is the load
exerted by the trailer on the coupling
ball. It can be varied by changing the
weight distribution when loading the
trailer.
The maximum permissible vertical
coupling load (75 kg) is specified on
the towing equipment identification
plate and in the vehicle documents.
Always aim for the maximum load,
especially in the case of heavy
trailers. The vertical coupling load
should never fall below 25 kg.
Rear axle load
The permissible axle loads (see
identification plate or vehicle
documents) must not be exceeded.