https://sites.google.com/site/njbbicycling/technical/gears
Derailleur Information - General
http://en.wikipedia.org/wiki/Derailleur_gears
http://sheldonbrown.com/derailer.html
http://www.stanford.edu/~dru/triplecheat.html
http://www.disraeligears.co.uk/Site/Home.html
http://www.disraeligears.co.uk/Site/Shimano_derailleurs.html
http://en.wikipedia.org/wiki/Shimano
http://en.wikipedia.org/wiki/Shimano#Mountain_bike_groupsets
http://www.velobase.com/ViewGroup.aspx?GroupID=2b81527d-bf9f-46e8-88b3-9f89ecc24221
http://www.infobarrel.com/Shimano_Mountain_Bike_Groupset_Comparison_-_Alivio_vs_Deore_vs_SLX_vs_XT_vs_XTR
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CALCULATING MAXIMUM DERAILLEUR CAPACITY
The following procedure allows you to calculate the derailleur capacity you will need given the chainrings and cogs:
Determine Maximum Chainring Difference by subracting the number of teeth in the smallest chainring from the number of teeth in the largest chainring [Rando's: 50T- 28T = 22T] [Possible new: 48-24 = 24T]
Determine Maximum Cassette Cog Difference by subtracting the number of teeth on the smallest cassette cog from the number of teeth on the largest cassette cog [Rando's: 30-13 = 17T] [Possible new: 34- 11 = 23T]
Determine Total Drivetrain Capacity (chain-wrap capacity*) by adding Maximum Chainring Difference to the Maximum Cassette Cog Difference [Rando's: 22 + 17 = 39T] [Possible new: 24 + 23 = 47T]
Record the Maximum Cassette Cog (the number of teeth on the largest Cassette Cog) [Rando's: 30T] [Possible new: 34]
* Chain-wrap capacity is a number that tells whether or not a derailleur will be able to do this on the drivetrain you plan to use it on. Calculate chain-wrap capacity with this formula: Chain-wrap capacity = (large chainring - small chainring) + (large rear cog - small rear cog). Example: 53/42 chainrings and a 12-23 cassette: (53 - 42 = 11) + (23 - 12 = 11) = 22-tooth chain-wrap capacity."
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For Shimano derailleurs:
SS - Short Cage Road Double - Maximum Cassette Cog is 27 and Total Capacity is 29
GS - Medium Cage MTB/Road Triple - Maximum Cassette Cog is 34(MTB)/27(Road) and Total Capacity is 33(MTB)/37(Road)
SGS - Long Cage MTB - Maximum Cassette Cog is 34 and Total Capacity is 45
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