catalin
This tractor weights in probably at about 8 tons and is allowed to be loaded up to 26 tons (7.5 on front wheels, 11.5 on drive and 7.5 on the rear lift axle, but total no more than 26 tons) so there are about 18 tonnes needed on the tractor to fully load it. the trailer adds on the truck 3 or 4 tonnes, maybe, so lets say 14 tonnes of that load need to rest on the tractor so I think this is about right.
That what happens when is raining and the truck was pointing uphill which made the ramps steeper.