My 2005 X5 exhibited vibration cruising from around 50 to about 70 MPH and it would get worse on braking at those speeds (steering wheel got pretty jumpy). Have had upper and lower control arms replaced as well as thrust arm bushing. Still presented as above. Local indie shop (Ace Auto, Norwalk CT) diagnosed as transmission mount. New tires at the same time were mounted and balanced. X5 feels like new with 164k miles. Hope this helps.