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How many chain links?(12 posts)

How many chain links?trogdor
Aug 20, 2003 6:05 AM
Recently I swapped out my rear cassette on my 650c bike from an 11-21 to a 12-25, 8-speed Ultegra. The front rings are 55/42 and will likely remain. Since the 12-25 rear cassette is new I got a new chain and need to remove some links.

Given the configuration stated above what is the standard chain length?

Thanks
re: How many chain links?Rusty Coggs
Aug 20, 2003 6:43 AM
Put the chain on the big ring, big cog,not through the derailer,pull tight and overlap,add 1".
Ok, will check that out tonight. . .trogdor
Aug 20, 2003 6:55 AM
Thanks!
the right way...C-40
Aug 20, 2003 9:15 AM
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.
Most impressive. . .trogdor
Aug 20, 2003 9:33 AM
Thanks for your input, very helpful!
the right way...Rusty Coggs
Aug 20, 2003 9:52 AM
The other way works for Sheldon Brown,and has never failed me. It's not that there is a right and wrong but,there are several ways.
I will likely do both. . .trogdor
Aug 20, 2003 10:24 AM
Thanks for the input.
it works but...C-40
Aug 20, 2003 11:29 AM
If you set the chain length with a 23 largest cog and later switch to a 27, you may get a nasty surprise if you shift to the 53/27. The "best" way makes sure that the chain will handle any combo within the derailleurs stated range.

If you want to intentionally exceed the stated capacity, setting the length on the largest cog/big ring combo would make sense, but I would never bypass the derailleur. Threading through the derailleur insures that the cage length is accounted for.
it works but...Rusty Coggs
Aug 20, 2003 12:08 PM
Corect that the small/small takes into acount the capacity for the derailer,but that also assumes one is not using a short cage with a triple which can also be done. FWIW doing Big/big without going through the derailer on a long cage also works.Did it the other day, and then checked results. It should be obvious,but probably isn't to many that they should check both extreme combinations just to be sure.
Try both methods and I think...PsyDoc
Aug 20, 2003 10:58 AM
...you will be pretty close to having 106 links; a chain that measures 53" long.
Try both methods and I think...trogdor
Aug 20, 2003 12:11 PM
Are you using a similar specification, i.e. 55/42, 12-25?
Yup, 106 for most setups (nm)Kerry Irons
Aug 20, 2003 5:27 PM