As I look through the post here, I see a lot of members going from 16" to 19" or even 20" rims. This has to through the speedo off. Doesn't it? I ask because I'm planning on going the other way. I've got 17" swoopies on my SSEi but I kept my snow tires and rims from my 95. The rims are stock 16" with standard size sidewalls (225/60/16). The new Bonne runs 235/55/17. I'm guessing the sidewall difference will make my speedo be close enough. Any thoughts?

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

when your speedo reads 60 mph, you will be travelling at 58.8 mph

Hmm, handy tool.... thanks Pat!