Quote:
Originally Posted by 93Cobra#2771
The pariticular upsize I have chosen is within .2% of the oem size tire. That is, if my memory is correct. I'm posting from my phone and too lazy to look at the miata tire size calculator.
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Tire calculators will only give you a very general notion of a tire's actual diameter or circumference. The sidewall numbers are "general guidelines" only, and the exact size of a 205/60-16 tire (for instance) varies from manufacturer to manufacturer.
If you can, check on the Tire Rack website (or similar resource) to find the actual published diameter for that specific make and model of tire--or the revs/mile figure, which is roughly equivalent. Compare to whatever you are "used" to having on the car, or to the OEM tires if you can find the specs.
In general, you will lose a little bit of MPG going to a wider tire. It may very well not be enough to notice, though.
-soD