How to Calculate Tire Sizes for Miatas
- 1). Measure the width of the tire. For a Miata it should be 185 millimeters. Therefore a replacement tire can be about 3 percent narrower or wider. Anywhere from 180 to 190 will be safe.
- 2). Measure the ratio of the sidewall height to the section width. For the Miata this is 60. Therefore a replacement tire in the range of 58 to 62 would be acceptable.
- 3). Determine the rim diameter, which is 14 on the Mazda Miata. A 3 percent range for this would be 13.5 to 14.5. Any larger or smaller than this would lead to poor handling issues.
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