I was told that the extra equipment on a euro spec X5 includes stiffer springs at the rear to prevent too much sag and to allow for more vertical weight on the hitch. If you order the hitch from the factory, than you are allowed to tow 3500kgs, if it's an aftermarket install, you are only allowed to tow 2700kgs...
Anyways, I have a friend who tows a 5000kg boat+trailer with a X5 35d... other than it being not legal, he's had no problems with the car whatsoever...

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