One problem related to suspension noise has been reported for the 2006 BMW 5 Series. The most recently reported issues are listed below.
The front suspension makes loud noises when the car goes over bumps. I also find that I have to perform wheel balancing every 2-3 months, which is a lot more than other vehicles I have owned. I have taken the car in to the dealer, who stated that there is nothing wrong with the suspension, except for dirty bushings. I find this hard to believe.