Well, I've been kicking around the idea of getting some new wheels, so I started putting together all of the smart fortwo (451 specifically) wheel specifications I could. After rummaging through a few threads and compiling information, I thought I would post up a thread with all of the information in one convenient place for all to see and reference.
Correct me if I am wrong, but here is what I know of our wheels:
Front Wheels:
4.5 J x 15 H2
Wheels Offset: 0.93 in (23.5 mm)
Tires: 155/60 R15 74 T M+S
Rear Wheels:
5.5 J x 15 H2
Wheel Offset: 0.87 in (22 mm)
Tires: 175/55 R15 77 T M+S
Bolt Pattern: 3 x 112.5 mm