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Need help to change cassette and chain length(4 posts)

Need help to change cassette and chain lengthsteveF
Apr 18, 2001 5:25 PM
Please tell me what tools I need to change a Campy cassette. (Park Tool website is a good source for this, but they are down for revision.) Campy website says that I need a longer derailleur for this cassette, so I would need a longer chain. Please tell me how to determine the proper chain length to use. Thanks!
re: Need help to change cassette and chain lengthSpoke Wrench
Apr 19, 2001 6:08 AM
To determine chain length, wrap your chain around the big ring and biggest cog while bypassing the derailleur. Add 1" and you're good to go.
not the best menthod....dave
Apr 19, 2001 1:38 PM
This method may work, but certainly doesn't take into account the difference between long cage and short cage derailleurs.

The best way is to wrap the chain around the little ring, through the derailleur and around the smallest cog. Links should be removed until the lower pulley swings down slightly (applying minimum tension to the chain), when the ends of the chain are brought together. One more link should be removed, if the lower pulley barely moves and the chain rubs the upper pulley guide tab.

This setting insures that the chain will never hang loose, without tension, and insures that the maximum capacity of the derailleur is not restricted by a short chain. The little ring and little cog combo are not normally used, but if you get into it accidentally, you don't want a loose chain.

Changing the cassette requires a chain whip, and the splined lockring tool.
Sorry, Dave, I disagreeSpoke Wrench
Apr 20, 2001 6:55 PM
The chain sizing method I suggested wasn't just something I came up with. It is the technique that is recommended by Shimano, Sram, and Sheldon Brown.

The method I suggested will produce the shortest chain that will safely wrap the big/big combination. That is important because if the chain is any shorter than that, an attempt to shift into the big/big combination can damage the derailleur, the chain and the derailleur hanger on the frame.

Your concern about not allowing for differences in derailleur cage length is unnecessary. When the chain is in the big/big combination, the derailleur cage is nearly in line with the chain so the same amount of slack is appropriate regardless of derailleur cage length.