Welcome to the Werkz
Have a look at this site, its worth book marking. It will give you the details of your current wheels, the factory tire sizes etc, and then you can compare that to the gear your looking at.Felgen-Katalog - BMW-Treff - der Treffpunkt für alle BMW-Fans und -Fahrer
Another useful site to add to your favourites is Wheel-Tire size comparer - WWW.RIMSNTIRES.COM
it lets you insert your current tire and wheel details and then compares it to what you are looking at.
Good luck with it all, and post some before and after photos.