Tire Height:
This will calculate tire height based on the numbers on the side of your
tire. The stock tires on an IROC-Z with 16in rims are: 245\50\16. The
first number is the width in millimeters of the tire from bead to bead.
The second the aspect ratio of the sidewall as compared to the width -
in this example it's 50% of the width. The last number is the size of
the rim in inches.
Note: This is the size of the tire inflated and off the ground. When under load from the cars weight, the tire's radius is reduced by approximately one inch. This one inch reduction is fairly consistent with all types of tires and vehicles, although the lower the profile, the less reduction there is. I tested from Hondas to Jeeps.