Apparently a few of us were interested in G35 rims so this may apply to several members:
What are the implications of getting tires at 215/50-17 over 235/45-17? Both produce an almost identical diameter according to the link in the 4th gen FAQs
(http://www.miata.net/garage/tirecalc.html)

Also, I read the reviews on tirerack.com, but I was interested if anyone here has experience with Kumho tires.

TIA