I have the Sport button on my Z4 (6speed manual) it does nothing to the suspension - no dampers to change, it adjusts the electric "boost" of the steering and changes the throttle response. Remember all these cars have a "drive by wire" throttle so a sport button can change the responsiveness to your right foot. It is a lot of fun, but I turn it off in heavy traffic as it can make the car behave like a greyhound (not the bus) - as i see an opening go for it NOW!

Weather permitting I will report on how the sport button behaves in my 4.8 - 22hours to go.

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07 X5 E70 4.8i
04 Z4 E85 3.0