Mine do every once in awhile but nothing major--I have the Multicontour seats. I've located the problem on mine it's the plastic where the all of the seat adjustment buttons are at the bottom of the seat. I just move the seat a little forward or backwards etc and it goes away. I think the plastic just gets "stuck" in a certain position after awhile and starts to creak + I have the 20s so obviously over bumps the ride is stiff anyways.

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2008 X5 4.8
Jet Black/Black Nevada/Dark Burl Walnut
Adaptive Drive
Premium Pack
Tech Pack
Climate Pack
Sport Pack
20" Wheel Option
Premium Sound
Sirius Satellite
Rear DVD Entertainment
Multi-Contour Seats
Comfort Access
3rd Row Seat
Heated Front Seats
Running Boards
3M VentureShield Paint Protection Film