Probably not a fit issue, but your speedometer will read slower than actual speed by a small percentage. Use this tool to do a comparison of different sizes to see how much:
http://www.miata.net/garage/tirecalc.html
FWIW, BMW speedos read higher than actual and can be 5%-7% off and still remain “within spec.” So, running a slightly taller tire would reduce that error, if yours is the same – which I’m sure it is.