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Old 01-27-2009, 02:46 PM   #6 (permalink)
jwc
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Join Date: Sep 2008
Location: BC
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I switched from 185/60-14 to 155/80-13. The weight savings was 6 lbs per corner, but more significantly, the tire weight went down by 4 lbs each. When I calculated the inertia difference, 80% of the inertia is in the tire as the weight is concentrated further from the rotational axis. I calculated that this change would requrie about 20 lb-ft less torque for the same acceleration.

The results, the car accelerates way easier and you can really keep your foot out of it. It's very noticeable around town, less so on the highway. As far as FE, I don't have any numbers yet as the snow started falling and I put the heavier steel wheels and snow tires on.
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