When you change the size of the tire i know it throws the speedo off, so my question is, is there away to correct the speedo or does one have to get under the car and change the gears in the tranny?

um, just buy correctly sized tires, cause if you get em too tall, you are gonna lose performance too.

what size tires did you get/are you looking at getting?

it wouldnt be too noticeable (should most liekly be same) if you increase the width and reduce the profile.
check this to see whats the diff
http://www.miata.net/garage/tirecalc.html

Unfortunately there's no way to adjust the speedometer. It's not controlled by gears but the computer actually calculates your speed based on the rotation speed of both rear wheels. It averages the speed based on the specs of the stock wheels and tire size from the factory. I called not only Mazda North America, but actually talked to someone at Mazda Japan trying to find out how to recalibrate the speedometer. The answer is "it can't be"; the dealers can't, no speedo shop can and Mazda won't.

you might start here.

http://www.blackrobotics.com/

beers