on the subject...
a few months ago, I ended up placing a full size spare in the trunk on my 08: M5. I bought a BMW tire jack kit form local dealer. I already had a M5 wheel with a tire from my earlier E-60: 550 conversation of wheels. Even though, it is taking up space in the trunk but I have a slight little comfort in my mind that I have a spare which I can possibly change in case of emergency. Hope that I never need that service but just in case..
Thought that I let everyone know about this matter...