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 11-01-05, 05:56 PM #1 howsteepisit Senior Member Thread Starter     Join Date: Oct 2005 Location: Eugene, OR Bikes: Mecian Posts: 4,313 Mentioned: 3 Post(s) Tagged: 0 Thread(s) Quoted: 497 Post(s) 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
 11-01-05, 06:12 PM #2 tonyt Senior Member   Join Date: Dec 2004 Bikes: 1982 Bianchi Superleggera (restored with NOS campagnolo components), 1987 Bianchi Campione Del Mundo, 1995 Bianchi Denali (M900/950 XTR components, viscous cycles rigid fork, mavic ceramics), 1996 Specialized Hardrock (winter beater, 8 speed XT group Posts: 175 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Sum of the differences of the largest minus smallest teeth on both the cassette and chainrings.
11-01-05, 06:36 PM   #3
HillRider
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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

 11-02-05, 05:12 AM #4 Coyote! Guest   Bikes: Posts: n/a Mentioned: Post(s) Tagged: Thread(s) Quoted: Post(s) What does this metric tell us about the gearing?
11-02-05, 08:15 PM   #5
HillRider
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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.

 11-02-05, 09:12 PM #6 sydney Senior Member     Join Date: Jan 2004 Bikes: Posts: 9,428 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) ^^^....and even Shimano spec is pretty conservative,not an absolute.