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What is the most likely cause?

Old 01-02-12, 12:01 PM
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What is the most likely cause?

Okay, I have a friend, yes a true friend not me. Who recently had a new chain put on her bike by a LBS. Since getting the new chain installed she hasn't been able to shift to her large chain ring. So what is the most likely cause for this? Should the shop have adjusted her limit screws? Is her cable stretched too much, or using Ocam's Razor, did the employee at the shop mismeasure the new chain and cut it too short?

On my own bike at about the same time that she replaced her chain I also replaced my chain and haven't had any shifting problems. I even recently had my front derailleur cable replaced and again I haven't any problems with shifting.

If it isn't one of the three things that I've listed, what else could it be?

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Old 01-02-12, 12:28 PM
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Too short a chain would prevent shifting only with the large rear cogs, others would be unaffected. Ocam's razor - if the front derailleur is not shifting properly then something wrong with the front derailleur. Could be mis-adjusted, could be it was accidentally rotated when installing the chain. Just return it to the shop if practical.
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Old 01-02-12, 12:29 PM
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With the rear derailleur shifted into a middle or one of the smaller cogs, try shifting the front derailleur by hand or by pulling hard on the cable by hand to see if it does go to the big ring. If it does, you have a cable tension problem and just adjust out the slack. If it won't shift to the big ring that way it's probably a limit screw problem. Unless you are trying to shift in big-big, it's very unlikely to be a too short chain unless it's WAY too short.

BTW, was the new chain, the only thing the LBS was asked to do?
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Old 01-02-12, 01:24 PM
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Originally Posted by cny-bikeman
Too short a chain would prevent shifting only with the large rear cogs, others would be unaffected. Ocam's razor - if the front derailleur is not shifting properly then something wrong with the front derailleur. Could be mis-adjusted, could be it was accidentally rotated when installing the chain. Just return it to the shop if practical.
It was shifting fine prior to the chain being replaced. Sadly, the shop in question is going out of business.

Originally Posted by HillRider
With the rear derailleur shifted into a middle or one of the smaller cogs, try shifting the front derailleur by hand or by pulling hard on the cable by hand to see if it does go to the big ring. If it does, you have a cable tension problem and just adjust out the slack. If it won't shift to the big ring that way it's probably a limit screw problem. Unless you are trying to shift in big-big, it's very unlikely to be a too short chain unless it's WAY too short.

BTW, was the new chain, the only thing the LBS was asked to do?
The next time that I see her I'll suggest that.

Yes, as far as I know the new chain is/was the only thing that the LBS was asked to do.
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Old 01-02-12, 02:15 PM
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You've probably already asked this, but can she shift to the largest chainring if the rear derailleur is shifted to the smallest cog?

It doesn't seem likely that chain to be too short. But having said that, why would you alter any derailleur adjustments to replace a chain? You don't really even need to remove a wheel.

Is the chain the proper width for the number of gears? If they're going out of business maybe they used whatever chain they could find.
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Old 01-02-12, 02:29 PM
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Originally Posted by speedevil
You've probably already asked this, but can she shift to the largest chainring if the rear derailleur is shifted to the smallest cog?
I can't remember if I did or not. I'll ask her the next time I see her.

Originally Posted by speedevil
It doesn't seem likely that chain to be too short. But having said that, why would you alter any derailleur adjustments to replace a chain? You don't really even need to remove a wheel.
It was just one of a few things that I could think of. I agree, as I said at about the same time I also replaced my chain and have had no problems with shifting, so I couldn't see why she'd have a problem with hers.

Originally Posted by speedevil
Is the chain the proper width for the number of gears? If they're going out of business maybe they used whatever chain they could find.
I'm pretty sure that it is, they still had a good supply on hand of chains and cassettes, so I don't think that that is the case.
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Old 01-02-12, 05:35 PM
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It could be any of the possibilities and others also. Odds are that the shop simply failed to check and adjust the shifting when installing the chain, which IMO is something that should have been included.

A slightly narrower chain, or one with differently shaped outer plates would shift slightly differently and probably require some fin tuning of the FD.

The RD usually isn't affected by chain width, but a diligent shop would also have checked the RD limits. Not as much as a matter of obligation, but as one of "defensive medicine". If the RD limits had been off, for example because the hanger got bent since they were last set, the shop would likely catch the blame if the RD overshifted into the spokes soon after a chain replacement.

Years ago, when I was in retail, I learned the importance of a thorough check when taking repairs in. Otherwise, we'd end up, for example, charging to fix a front flat, and end up having to align the wheel and adjust the brakes for free. same with the simple task of switching a chain. Lots of other adjustments may be required and a diligent shop has to build that into their price.
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Old 01-02-12, 05:47 PM
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I agree with FBinNY (as usual). It's bad practice to just assume you can slap on a chain with no regard to the rest of the drive chain. That's not only poor customer service, it opens you up to liability. But we can only guess at what happened. The answer remains to return it to the shop if possible. If not, try it yourself or with a friend's help, or have another shop fix it.

Last edited by cny-bikeman; 01-02-12 at 05:50 PM.
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