I am thinking of getting a 5th gen. Can 225/40/18s be used on a 5th gen? According to the miata tire calculator site, 225/40/18 is 3% smaller than the oem 225/50/17 tire. Is this too small? Who here is running 225/40/18 on their 5th gen?

Thanks

 

3% isn't too far off. although 235 would probably be optimal.

 

I don't see any reason why you couldn't run 225/40/18, since it'll work just fine. 235/40/18 is the optimal size, and I'm running 225/45/18 with no problems.