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howsteepisit

11-01-05 05:56 PM

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

tonyt

11-01-05 06:12 PM

Sum of the differences of the largest minus smallest teeth on both the cassette and chainrings.

HillRider

11-01-05 06:36 PM

Quote:

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

Coyote!

11-02-05 05:12 AM

What does this metric tell us about the gearing?

HillRider

11-02-05 08:15 PM

Quote:

Originally Posted by Coyote!

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.

sydney

11-02-05 09:12 PM

^^^....and even Shimano spec is pretty conservative,not an absolute.

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