Actually, the stock tire is 215/45/R17 NOT 215/40/R17 like you listed.Originally posted by Daniel Isaiah@Aug 24 2005, 02:31 PM
Thats a rather big change in the wheel size/shape. according to this tire calculator: http://www.miata.net/garage/tirecalcold.html, a 225/40/R18 is 5.5% slower when it comes to Revolutions per minute at 60mph. Is this calculation wrong? the formula looks legit. So what it basicly is saying is that when the speedo is at 60mph, its actually going 63.3mph compared to the 215/40/R17 stock tire size.
what do you all think?
also, according to that same calculator, a 245/30/R18 would be the closest fit to stock diameter. But who on earth makes a 245/30/R18 ????