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Old 11-01-05, 05:56 PM   #1
howsteepisit
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How is total teeth caculated

Shimano, in addition to the largest and smallest rear cogs and chainwheels specs a total teeth capacity for thier rear derailiers. How is the total teeth calculated? Thanks
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Old 11-01-05, 06:12 PM   #2
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Sum of the differences of the largest minus smallest teeth on both the cassette and chainrings.
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Old 11-01-05, 06:36 PM   #3
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Originally Posted by tonyt
Sum of the differences of the largest minus smallest teeth on both the cassette and chainrings.
An example. Say you have 53/39 chainrings and a 12x25 cassette. The total teeth are (53-39) + (25-12) = (14) +(13) = 27
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Old 11-02-05, 05:12 AM   #4
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What does this metric tell us about the gearing?
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Old 11-02-05, 08:15 PM   #5
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What does this metric tell us about the gearing?
It doesn't. It tells you how much "capacity" your rear derailleur needs to avoid going slack in the "small-small combination. You can violate the recommendation by a bit if you avoid using the small chainring with the smallest few cogs.
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Old 11-02-05, 09:12 PM   #6
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^^^....and even Shimano spec is pretty conservative,not an absolute.
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