Changing Tires

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Henrythewound

Senior member
Oct 25, 2002
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i know what the term log scale means, but is my assumption/understanding of how a speedometer determines your speed wrong?
 

daveshel

Diamond Member
Oct 10, 1999
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Originally posted by: Henrythewound
i know what the term log scale means, but is my assumption/understanding of how a speedometer determines your speed wrong?

I don't think there is anything logarithmic about the operation of a speedometer. It just measures the number of revolutions of the wheel in a given time frame. So if a tire with a latger circumference is used, the car will travel farther per revolution, which means it will be going faster than the speedometer indicates. This variation would be linear.
 

iamaelephant

Diamond Member
Jul 25, 2004
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It's not a log scale, but the speedo will be off by only a tiny amount. Most speedos read slightly slightly high from the factory anyway (to avoid lawsuits from speed camera victims) so she'll be right. And it's spelled "tyres." Can you Americans please stop raping the english language?