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New chain length
Ok I have a standard double 53-39 with a 12-25 rear. I am going to go to an 11-28, realizing this is not the way to size a chain, but what is guess to how much the new chain will be longer? I am thinking just one more full link will be ok. Now I am going to measure and do it right but there must be some formula.
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There is a mathematical formula but I don't know what it is and everybody that I know uses the analog approach:
Run your new chain around the biggest chain ring and biggest rear cog bypassing your rear derailleur. Figure out the shortest place that you could rejoin the chain. Now add 1 inch of chain (2 links), including your master link, to that. That's the shortest chain that you can safely use with that gear combination. |
Originally Posted by Retro Grouch
(Post 18078246)
There is a mathematical formula but I don't know what it is and everybody that I know uses the analog approach:
Run your new chain around the biggest chain ring and biggest rear cog bypassing your rear derailleur. Figure out the shortest place that you could rejoin the chain. Now add 1 inch of chain (2 links), including your master link, to that. That's the shortest chain that you can safely use with that gear combination. Park explains it here at the bottom: Park Tool Co. » ParkTool Blog » Chain Length Sizing And someone made a javascript calculator webpage here: Javascript Bicycle Chain Length Calculator Instead of using Big/Big, use Small/Small such that you chain clears the pulleys by ~1cm (IIRC the Campag manual says 8 to 15mm). The difference is that instead of sizing your chain for the shortest chain length, you size for the largest sprocket size your derailleur can handle. Now, using an 11-28 odds are you'll never use a larger cassette, but you never know. |
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