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trainwreck
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Discussion Starter · #1 ·
so im new to the whole mtb scene and was wondering what the difference between a long cage and short cage derailleur i just bought a oldschool 95 kona aa and am tring to build a all mountain bike under 20lbs also i was wondering what sort of gearing should i go for.
any advice would help thanks
 

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~Disc~Golf~
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16,496 Posts
galbeithnoobie said:
so im new to the whole mtb scene and was wondering what the difference between a long cage and short cage derailleur i just bought a oldschool 95 kona aa and am tring to build a all mountain bike under 20lbs also i was wondering what sort of gearing should i go for.
any advice would help thanks
Shorter cages help with chain slap and are less likely to be snagged by a twig or strike a rock.
The longer cages are needed to accommodate the 'tooth capacity' of your drivetrain. Basically, the more and bigger (size) gears you have, the longer cage you need.

To calculate your bikes tooth-capacity, take the difference of the tooth count in the rear cogs (largest-smallest) and add it to the difference of the front chain-rings (largest to smallest)

Example:
(32-11)+(42-22)= 21+20=41

You would need a derailleur with a minimum tooth capacity of at least 41
Generally tooth capacity is as follows
Shimano long = 45T; medium = 33T
SRAM long = 43T; medium = 37T; short = 30T

In the above example, you can see that you'd need a Long cage.
 
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