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Shimano 8sp chain length(6 posts)

Shimano 8sp chain lengthWannabe
Jun 7, 2002 7:59 PM
Upgrading bike from 7sp to 8sp. How long should my chain be? Where can I find info on this. the shimano site was no help!


The unanswerable questionKerry
Jun 8, 2002 5:22 PM
First, you have to tell us what your cog sizes were and are, and then your chainrings, and then your chainstay length, and even then it's a bit hard to calculate. Perhaps a better way to answer is that for every 4 teeth added to the largest cog in the back, you add two links (one inch). Unless you made significant changes in the rear cluster, you probably don't need to change chain length at all unless you were right on the edge already.
here's the answer...C-40
Jun 8, 2002 6:57 PM
Two simple tests will determine if the chain is the correct length. First, it must not hang loose in the little ring, little cog combination. If there is no tension on the chain in the little ring, little cog combination, remove two links (one inch) at a time, until there is. When the ends of the chain are brought together, some movement of the lower pulley should occur, indicating tension is being applied. Two more links (another inch) may need to be removed, beyond the point of absolute minimum tension, to keep the chain from rubbing on itself as it passes under the upper derailleur pulley. Once this is done, the chain is set to the maximum useable length. Removing additional links will do nothing but reduce the derailleur's capacity. It won't help keep the chain from skipping or jumping.

Second, the chain must be long enough to avoid overextending the rear derailleur when shifted to the big ring and biggest cog combination. If the chain is set to the maximum length as described, it should always pass this test, unless your setup exceeds the derailleur's stated capacity.

If you want to see how much lower pulley movement will occur, without removing the extra two links, shift up four teeth (11 to 15 or 12 to 16). This has the same effect as removing two links.
re: Shimano 8sp chain lengthrider5673
Jun 8, 2002 5:30 PM
Got a fax #? I can fax a diagram from the instructions on the last chain I bought. E-mail me at
re: Shimano 8sp chain lengthB2
Jun 9, 2002 6:53 AM
I've always done it this way without any problem. This assumes your derailleur has adequate capacity of course.
Thanks! nmWannabe
Jun 9, 2002 9:24 AM