I now have 275/65/18 and was going to buy new tires and go a little bigger.
However the dealer only has 285/60/18. Can anyone tell me the how much taller and wider the new tires would be from my stock? Should I try and find 285/"65"/18? Id like to go big as I can with a 285 tire and not sure how much the 60 and 65 differ in the tire size.

Thanks!!

 

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

this is the best comparison calculator I've seen on here

 

Here's another calculator that you may like better:

http://www.discounttire.com/dtcs/infoTireMath.dos