HOWTO: Choose the Correct Tire Size
Written by Wild Weasel
When replacing the wheels on your car, it is important to
choose the correct size tire to maintain the stock wheel height.
If you go with something other than the proper size, both your
speedometer and your odometer will end up reading incorrect values.
Some people choose to go with a different size than stock in order to race
or to have a lowrider look but in general it is not recommended.
If you DO decide to change your tire height, you should bring your car
to an authorized dealer to have the computer recalibrated for the new size.
This applet will show you exactly which size tire to choose for any size rim
you'd like. It will also show how far off your speedometer will be if you choose
a different size.
Note that the actual tire height will never be exact, as factors such as the width
of the wheel can have a minor effect on the resulting height, but this will give
you an idea of what tire you should get to be as close as possible to what you want.
Special thanks to Miata.net for the calculator.