Driving and operating 177The permissible trailer loads arespecified in the vehicle documents. Ingeneral, they are valid for gradientsup to max. 12 %.The permitted trailer load applies upto the specified incline and up to analtitude of 1000 metres above sealevel. Since engine power decreasesas altitude increases due to the airbecoming thinner, therefore reducingclimbing ability, the permissible grosstrain weight also decreases by 10 %for every 1000 metres of additionalaltitude. The gross train weight doesnot have to be reduced when drivingon roads with slight inclines (less than8 %, e.g. motorways).The permissible gross train weightmust not be exceeded. This weight isspecified on the identification plate3 229.Vertical coupling loadThe vertical coupling load is the loadexerted by the trailer on the couplingball. It can be varied by changing theweight distribution when loading thetrailer.The maximum permissible verticalcoupling load (75 kg) is specified onthe towing equipment identificationplate and in the vehicle documents.Always aim for the maximum load,especially in the case of heavytrailers. The vertical coupling loadshould never fall below 25 kg.Rear axle loadWhen the trailer is coupled and thetowing vehicle fully loaded, thepermissible rear axle load (seeidentification plate or vehicledocuments) may be exceeded by60 kg, the gross vehicle weight ratingmay be exceeded by 60 kg. If thepermissible rear axle load isexceeded, a maximum speed of60 mph applies.Towing equipmentCautionWhen operating without a trailer,remove the coupling ball bar.Stowage of coupling ball barThe bag with the coupling ball bar isstowed in the rear stowagecompartment on the floor.Place the strap through the lashingeye, wrap around twice and tightenthe strap to secure the bag.
