let me explain, i want 18's (hre's to be exact) but i do not want my speedometer to be inacurate, nor my car to be slower, so what size tires do i need to get so that 18 inch wheels and tires are as big as the stock 17's with teh stock tires.
P.S does anybody knoe what the power distribution is for the 01 (how much % in back and front), because i kind of want somewhat of a lip.

 

oh c'mon nobody?

 

Typicaly everyone runs 225/40/18. That could argueably give a little more wheel gap. Do a search im sure its been researched to death.

 

You want to stay within +/- 3% of the original wheel/tire combo. Go to http://www.miata.net/garage/tirecalc.html and put in your stock tire size. Then put in the tire size for the 18's and compare the difference. But as said before 225/40/18 or 235/40/18 are probably going to be the most popular sizes.