So my X5 has been back to the dealer for the third time now. I'm OK with it because I get a loaner car (2006 325i last time 2006 X5 3.0) Last time they replaced:
front both sides axle sensors - the theory was that the sensor was faulty, it regulates the outside/inside wheel as slow/fast and would adjust
front both sides ride height sensors - regulates when the vehicle is low/high (they did check the air bags and last time set the vehicle to level and reset the "brain")

So this was last week. When I first picked up the vehicle it was fine, the svc tech told me they test drove it and the shop/tech foremen seemed to know his stuff. After driving a couple of days my parking garage guy told me that my X5 seemed to be lower again on the front passenger side...PISSED! I started to test the "axle rubber/grinding thing" it came back.

So it was discussed the grinding sound might be rubbing on/in the fender well but that was not the case.

Currently: they are replacing wheel/rotor sensors same concept slow/fast when turning. The ride height is still a mystery and they get back to me.

-pierre