I am looking at a set of rims with tires and am just wondering if this size wil fit correctly. Thanks

 

Just perfectly, and your speedo hardly gets affected..

Check it out for yourself, http://www.miata.net/garage/tirecalc.html

 

Yes. But it depends on the width of the rim and the rim's offset. Just asking if 235-45-17 will fit is not a fair question becuase we do not know enough information. 17x8 rims w/ about 35-38mm offset on the 4-gen should be fine.