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Old 11-18-07, 06:50 PM
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operator
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Join Date: Jun 2004
Location: Toronto
Posts: 28,353

Bikes: 1987 Bianchi Campione

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Originally Posted by jc808
I just picked up my first computer. I need to figure out the circumference of my wheel to calibrate it, and It's giving me a bit of trouble. My wheel is 700 x 25.

Here's the formula I followed, as per the manual:

distance from floor to hub: 13 3/8" (13.375)

multiply by 25.4 to convert to mm (339.725)

multiply that number by 6.28 (2 x pi) = 2133.473


I had entered 2105 based on Sheldon Brown's recommendation for a 700 x 25 wheel. But this is a pretty substantial difference. When I entered 2133, it seemed like the miles were racking up really quickly. I'll be the first to admit that I don't have the best sense of distance, so I could be wrong.

Any ideas?
Don't worry too much about absolute accuracy. The important thing is consistent. You can also verify it against gmaps pedometer for distanced travel. As you ride more you'll realize that all this bike computer stuff is just fluff.

Real joy is riding.
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