My tires are 225/60R15. The spare is a 240/45ZR415 which is about a 16" rim. The rims on my car are steel with BMW hubcaps but the spare is an aluminum rim, so I don't know if they are the original wheels.
By the way, Thanks a lot for the parts info. Now I can have less headaches about buying parts. Getting them through a dealer can be very expensive.