This may sound strange, but for how I use my Z, I'm quite pleased with the performance and look of the 16" 104's on a 2.5. Some of the 18", and 19" combinations make the car look like a tractor, or worse - a Solstice. I do like the OEM 18" 125's though, but I'm concerned about the effect on performance with the additional weight. Can anyone provide feedback regarding the effect on performance with the larger wheel/tire combinations. I'd prefer to stick with BMW wheels rather than other brands.

I went from the 16" non-sport wheels to 18" 107s to 18" 108s (okay, I never mounted those, I sold them on right after they got here) to 18" ZHP replicas (not shown - yet). Because of the choppy ride and heavy weight of run-flats, going to 18" wheels with regular tires results in ride improvement and no weight gain to speak of.