Thanks for the reference. In additon to the additional weight of the 750i over the 550i, the 7 was tested with the 6-speed transmission. The 550i has an eight speed. This should cut even more time from the 550i. So, the estimated 550i times should be around 4.6-4.7 seconds which is just about what my E39 M5 was, ie 4.7 seconds. The 550i xDrive should be around 0.2 seconds faster.
Originally Posted by tadtaggert
Road and Track has a comparison of the 750i vs. LS 460, they quote the 750i as 0-60 in 4.9. I can't imagine the 550i not being at least a bit faster, so maybe it's faster than what I expected (which was about 4.9).
550i xDrive/ImperialBlue/Beige/anthracite/DHP/sport/vent seats/convience/cold weather/driver assistance/prem 2/sport trans/fold down rears/4 zone/ACC/HUD/cameras/night vision/ipod and smart integration.