BMW Z4 Forum : “My rear tires tip in at the top- or out at the bottom. Why”

Hi Roger! What you are referring to is camber. There is a tilt, if you will, to tires on all cars to ensure the proper amount of tread meets the road. Only your mechanic can tell you if the camber is properly set on your rear tires however one symptom of a problem is uneven or accelerated  wear on your tires. If you are concerned put it in front of your favorite wrench to check it out. Good luck!