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recurring chain-slipping problem

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recurring chain-slipping problem

Old 07-06-06, 11:35 AM
  #1  
Eli_Damon
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recurring chain-slipping problem

Please tell me if you have any ideas about what's going on here. I'll be riding along with no problems. Eventually my chain will start slipping and/or making a lot of rattling noise. By "slipping", I mean that it fails to grip the gear teeth reliable so when I push on the pedals, the pedals move in jerks but the wheels don't move that much. The problem is more noticeable when the chain is on the smallest or middle chainring rather than the largest chainring. It is also more noticeable when I am going uphill. When this happens, I take my bike to the shop to have it adjusted and when I get it back, it works fine. However, after a trip or two, it comes back.
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Old 07-06-06, 12:50 PM
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could it be shifting related? shifting too far at once, or the gears shifting automatically on you? -- what kind of shifters do you have?
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Old 07-06-06, 01:05 PM
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Originally Posted by godspiral
could it be shifting related? shifting too far at once, or the gears shifting automatically on you? -- what kind of shifters do you have?
I have bar-end friction shifters. When the problem occurs, I can usually, mitigate it by adjusting the shift-levers but I have to do this frequently and it doesn't go back to normal.
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Old 07-06-06, 01:06 PM
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How old is your chain and cassette? Sound like they could be worn.
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Old 07-06-06, 01:18 PM
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Sticky link in the chain? Spin it backwards and watch the hanger wheels for movement, find the sticky one and get it loosened up...
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Old 07-06-06, 01:38 PM
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The LBS is adjusting the shift cable, but not adressing the real problem, which sounds like friction to me.

When you shift to a higher gear, the shift cable pulls directly on the derailer, so it's gotta move. When you shift to a lower gear (like on hills) the cable goes slack and a spring in the derailer pulls the derailer into position. If the cable is not free to move, you have the problem you describe. Do this:

1. Lubricate all 8 pivot points on the rear derailer.
2. Lubricate the shifting cable. Position the bike so you can drip light oil into the cable where it connects to the rear derailer.
3. Turn the bike upside down and lubricate the place where the shift cable slides against the bottom bracket. (This is where the problem usually is for me)

Let us know how you make out.
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Old 07-06-06, 03:10 PM
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there is a good chance that your cog and chain are worn. Its a common problem, the smaller the cogs 5,6,7 wear faster because there is less teeth on them than the cogs with larger teeth.

Also check for a stuck link. Either way it is not something that can be fixed with an adjustment.
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Old 07-06-06, 04:31 PM
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The cassette is brand new. The chain is old but does not appear to have any stiff links.

JavaMan, I tried your suggestion of libricating the derailleurs and derailleur cables but I didn't get a chance to test-ride it because the bugs were swarming on me so I did not want to stay outside. I will test-ride it tomorrow and report back.

While I was fiddling around down there, I noticed that when the shift levers are in the position that puts the least tension on the cables, both cables are loose, that is, there is no tension on them and they sag. Is this a problem and, if so, could it be THE problem?

Thanks for your suggestions, all. Eli
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Old 07-06-06, 06:00 PM
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The solution javaman describes is if you attempt to shift to a smaller cog and it dosn't shift or is delayed.

If your problem is that it shifts to smaller gears all on its own, the barends may not be holding the cable tension. There are big screw heads on the side that need to be tightened.
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Old 07-06-06, 06:52 PM
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if your casette is brand new and your chain old, they might not be jibing together. If a chain and casette have been well used -together and for a long time- and one is replaced, it is a good idea to replace the other.

Replace the chain and see how it goes...
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Old 07-06-06, 09:57 PM
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Originally Posted by Eli_Damon
JavaMan, I tried your suggestion of libricating the derailleurs and derailleur cables but I didn't get a chance to test-ride it because the bugs were swarming on me so I did not want to stay outside. I will test-ride it tomorrow and report back.

While I was fiddling around down there, I noticed that when the shift levers are in the position that puts the least tension on the cables, both cables are loose, that is, there is no tension on them and they sag. Is this a problem and, if so, could it be THE problem?

Thanks for your suggestions, all. Eli
Now you are making progress, testing, observing, and aquiring your own knowledge. Good job!

While the cable is sagging, try pushing the derailer toward the wheel. If the cable tightens, there is too much friction somewhere for the spring to overcome. If the cable doesn't tighten, then the LBS did not adjust it right.
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Old 07-07-06, 02:44 AM
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Just to reiterate a point already made above....new cassette and old chain = problems. Ideally you should change both together as they wear in unision.

However, to me your problem just sounds like too much slack in your shifter cable. Try turning the barrel adjuster a few times and see if that helps. Otherwise it could be the chain - cassette thing.
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Old 07-07-06, 09:44 AM
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It helps to determine whether the "slipping" is the chain slipping on the same cog (which indicates the wear type of issue), or whether it is slipping because it is jumping onto another cog aka "autoshifting". The latter is either a tension adjustment or potentially a bent derailleur. Good stuff on sheldonbrown.com on this topic.
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Old 07-07-06, 12:05 PM
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I had the derailleur cables tightened and it seemed to help. We'll see if the problem develops again though. Thank you all for your advice.
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