i was asking a costco dude in the tire shop how my getting 18" or 19" on my FD would effect the speedo and he popped out this cool as heck windows program that had a "bridgestone" tag on it.

it let you stick in your stock and your new wheels and output speedo-guages that showed you the ORIGINAL and NEW indicated speeds. It was a cool program and I'd love to know where I can get it... anyone?

david

 

http://www.bigcustomwheels.com/info_specs.jsp

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

 

 

You also have to remember that a 245/45/16 Bridgestone may not be the same as the same size tire made by another manufacturer. Tire sizes shouldn't vary, but they do.