Quote:
Originally Posted by Enigmus
I assumed that the stock Michelins were 215/45/17 that it wouldn't change in overall size with 235/45/17. Plus 235/40/17 were more expensive because of limited tire selections.
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ah, just FYI you assumed incorrectly. the "45" portion of the tire size is not a direct indication of sidewall height. "45" actually indicates that the sidewall is 45% as tall as the tires are wide. So if the tire is 215mm wide, the sidewall is 215 x .45 = 96.75mm (3.8in) tall. By stepping up to a 235/45, you are now running a sidewall that is 235 x .45 = 105.75mm (4.2in) tall. Since there are technically two sidewalls in a circle (the bottom and the top), you multiply the sidewall height by 2, so 8.4in now vs 7.6in before.
Effectively, you increased the overall diameter by .8in. You may or may not care about the effects of said change, but it will throw the speedometer off by ~ 3%, and change your effective final drive ratio (making it taller), therefore reducing torque output to the ground by a bit.