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Help ! Chain lenght ok?(17 posts)

Help ! Chain lenght ok?noupi
Aug 16, 2003 2:55 PM
Often when i stop pedalling and start the chain will
skip (a clunck sound) but OK after .
Dura ace shifters with full Ultegra the shifting is flawless
up and down
Here are 2 pics large 50 with large 27 back
re: Help ! Chain lenght ok?noupi
Aug 16, 2003 2:56 PM
How bout a different pic!the bull
Aug 16, 2003 3:03 PM
Small gear in back and small in front.
(Looks long) nmthe bull
Aug 16, 2003 3:06 PM
How bout a different pic! OK!!noupi
Aug 16, 2003 4:10 PM
YES TOO LONG!the bull
Aug 16, 2003 4:54 PM
Take out some links until there is a little tension on the deraliuer.
sure about that?C-40
Aug 17, 2003 7:47 PM
Mostly wrong answers to this simple problem. If the chain does not rub on itself as it passes under the upper pulley it is not too long. It does look like you coulg get by with removing 1 inch of chain, but absolutely no more.

Here's the proper procedure:

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.
Try this:Spoke Wrench
Aug 16, 2003 5:33 PM
1. Wrap your chain around the big cog in back and the big front chainring BYPASSING the rear derailleur.

2. Add one inch of chain.

I'm thinking you have about four links too many right now.
Try this:High Gear
Aug 17, 2003 5:31 AM
I wouldn't use the methode of bypassing the derailleur. The propper way is to run the chain through the derailleur and onto the largest cog in the back and large chainring, pull the chain tight till the derailleur fully extends, then add a link to that. The idea is to not have a chain that is so tight that it would bend the derailleur if cross-chained. Also not too sloppy loose that it impedes shifting. We'll talk about the "B" adjustment screw another time.
Try this:Spoke Wrench
Aug 17, 2003 8:53 AM
That's the method suggested by both SRAM and Shimano so I'm in some pretty good company.
Not to get into a pissing contest but......High Gear
Aug 17, 2003 10:15 AM
I seem to remember Shimano had a little tech sheet in with the chain that showed a diagram. Can't really remember the gear combo but it was somthing like big chainring and a center cog combo should produce a vertical alignment of the two jockey pullys. I can't recall any of this "run the chain from large to large bypassing the rear derailleur and add an inch" Anyone remember seeing that in the Shimano literature?
I'll get my raincoat on...The Walrus
Aug 17, 2003 1:15 PM
I'm looking at a Shimano "Rear Drive System" service instruction sheet for the RD-M750/M570 derailleurs, and one for the SRAM ESP 9.0SL rear derailleur, and they clearly show the "proper" method as large chainring/large cog, bypassing the derailleur, and then adding two links.
I'll get my raincoat on...High Gear
Aug 17, 2003 3:05 PM
Must be something new with Shimano. I remember it the way said above. I haven't used Shimano in about six years. I guess that way works too. I never tried it or heard of using that method. Sorry Spokewrench for doubting you.
Lennard Zinn say to ...Live Steam
Aug 17, 2003 3:58 PM
for a double- run the chain through the rear derailleur and then around the large chain ring and small cog so that the rear der. aligns vertically. For a triple - bypass the rear der. and wrap the chain around the big chain ring and big cog and add one link. He is the master!
Take out one link (nm)LC
Aug 17, 2003 7:41 AM
re: Help ! Chain lenght ok?Duc9
Aug 18, 2003 12:47 PM
Since you haven't mentioned how this came to be, your chain may have stretched beyond a safe length. Before removing any links I would check to make sure the chain is still safe to use. You can test the length with a specific chain measurement tool available from most shops.
Bike was built up like that.noupi
Aug 19, 2003 3:39 PM