I like this tire calculator
http://www.miata.net/garage/tirecalc.htmlI’ve had 185/60r/14 Cooper Cobra G/T tires on 87 RX7 rims. They were a nice all season tire that really squealed when spun out.
Later I replaced the rims with 17” RS limiteds with a 42mm offset and put 215/35r/17 Yokohama S Drive tires on them. Awesome handling that rode smooth and quiet, but my speedo still read fast.
They wore out after 30K miles and I replaced them with Kumho Ecsta Sports with a 40r wall height to make the speedo read correctly.
I must admit that these tires are smoothest and quietest tire I’ve had and perform well over 110+ mph. Too bad they only seem to last 20-25K miles.
My next set of tires will probably go with Yokohama again.