148 Driving and operatingFor trailers with low driving stabilityand trailers with a permitted grossvehicle weight of more than 1300 kga speed of 50 mph must not beexceeded; the use of a stabiliser isrecommended.If the trailer starts snaking, drive moreslowly, do not attempt to correct thesteering and brake sharply ifnecessary.When driving downhill, drive in thesame gear as if driving uphill anddrive at a similar speed.Adjust tyre pressure to the valuespecified for full load 3 207.Trailer towingTrailer loadsThe permissible trailer loads arevehicle and engine-dependentmaximum values which must not beexceeded. The actual trailer load isthe difference between the actualgross weight of the trailer and theactual coupling socket load with thetrailer coupled.The 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 198.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 by90 kg and the gross vehicle weightrating by 75 kg. If the permissible rearaxle load is exceeded, a maximumspeed of 62 mph applies.Towing equipmentCautionWhen operating without a trailer,remove the coupling ball bar.
