What size tires should I get with 18x9.5 Z06 wheels with 53mm offset? My car is a 91 Z28 1LE. It's the factory ride height right now, but I want to lower it 1.5" with the Eibach Pro Kit. Will 2" adapters work?

275/35/18 is the most common and a good fit for a 9.5 inch rim. i dont know about the adapters tho.

www.tirerack.com doesn't seem to have tires that size, but they have 265/35 and 275/40. I'd like to get BFGoodrich g-force KDW's.

I am going to go with 275/40/18 Khumo MX tires for the back from tire rack when I sell my 17s and get 18s. They are a little taller thank stock hight. when your speedo says 60 it will actualy be at 62mph.
Plus less chance of denting a rim.

check this out too. http://www.miata.net/garage/tirecalc.html]Tire size calculator [/URL]

I guess I'm going with the Bridgestone Potenza S-03 Pole Position 275/35YR18. Killin me with the price of 18" tires.

yeah, that's why I like the Khumos, There supposed to be better than Good year Eagle F1s but only cost $174. each