Hi - have a 2005 V6 and my tires need to be replaced. Have been looking to upgrade to a set of GT take-offs. Not being very mechanical - does it matter that they are a different size? I would think it would have some effect on the speedometer?? Thanks in advance for your help!

 

You should be able to get a tire that while it is on a 17" wheel is roughly equivalent in dimension to your stock 16" wheel and tire. My car came with the 17" bullitts and 235 - 55 - 17 Pirelli's that are about 27" tall. My drag radials were mounted on a set of 16" stock wheels that I bought and are 255 -50 -16 and are just over 26" tall.

I found a tire calculator on the net that you can use to compare your current tire size with a 17" tire:
http://www.miata.net/garage/tirecalc.html