Hi all,
Don't know if it's been posted before, anyway if it was here it is again.
As I'm mucking around with my suspension at the moment I was trying to work out the tyre sizes and came across this site:
http://www.miata.net/garage/tirecalc.html
You plug in what tyre you have and what you want and it will give you the dimensions and also how much your Speedo will be out by (much easier than working it out with a calculator)
Bill