Does anyone know what various tires fit a stock wheel for the P5?

I've done a search and learned about what the measurements mean and found the calculator: http://www.miata.net/garage/tirecalc.html

But what I couldn't find was whether a slightly taller tire, such as a 195/55R16 would fit. Would it rub against anything? What about 185/55 or 60 series. Do they even make them? I know it would probably throw the speedo off a bit. Would it look silly?

Basically, I was just curious if there was a good tire that would give me a little more clearance if I drive on some dirt road trailheads. Would you recommend going with a smaller wheel instead, and if so, what size wheel/tire combinations do you recommend.

Thanks in advance!!

P.S.: What does "offset" mean?
thanks

 

You could put 205/50 on if you don't mid going wider as well as taller.

Compomotive has a good discussion of wheel measurements:
http://www.comp.co.uk/info/technical.htm