I have 235 on 8.5 rim right. With 245, how much will my speedo be off? Anyone have that tire calculator software that they can plug in the numbers for me?

 

Always had tha link handy for me, maybe he can help Tony

 

here is the site

http://www.miata.net/garage/tirecalc.html


it is about 1.602115414527936 % to slow..


that site is very percise with there numbers..

 

From my calculation, the stock (215/55/16) diameter is 79.5" va the 245/40/18 diameter of 80.8". A difference of 1.6%. Hope that helps.

 

Hmmm...with 235/40/18...it's .35xxx % to slow
with 245/40/18 it's 1.6xxx % to slow.

Wow...i guess 235/40/18 is the most optimal choice. But I do want a wider tire for more wheel protection, so I guess I can live with the speedo/gear ratio more off.

Ok...245/40/18 will be my next set of tires.

 

nm