I rub some with my +43mm 18x7.5" wheels with 225/40-18 tires on my 6th gen Sedan. Chances are you will have some rubbing, and it may or may not be a problem depending on how much weight you carry on a regular basis, whether or not you have rear camber correction, and what your rear spring rates are...
I suggest you get 215/40-18 to eliminate rubbing, but you will have less sidewall (don't know if that'd be a problem). However, 215/40-18 tires will fit nice and square on the 7.5" wide rim, so it could reduce sidewall flexx and improve cornering if you're feeling adventurous
Also the 0.1" decrease could help imrove your gearing, lol
http://www.miata.net/garage/tirecalc.html
Originally Posted by MrChad
My Racing Hart M5's are +42mm offset running Eibach Prokits and camber kit, I don't rub at all in the rear. But I'm a coupe.
yeah, the 6th gen coupes seem to have even more clearance than the sedan. That's also the reason why a 1.5" drop looks lower on a sedan than on a Coupe (coupe has more wheel gap due to higher cut fenderwells).
Just seems as though people with your setup who claim they don't rub have coupes :dunno: