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Front Derailleur Cable Guide on My Tandem

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Front Derailleur Cable Guide on My Tandem

Old 03-19-09, 07:35 AM
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Equinox
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Front Derailleur Cable Guide on My Tandem

I've been having trouble with the front derailleur adjustment. It is a triple. My shop will adjust it so I don't have chain rub, but the problem returns after a couple of hundred miles. I was looking at the bottom of my bike. There is a brazed on guide tube for the cable. The tube has a gap in the middle. My cable does not go through the entire cable guide. It only goes through the rear half of the tube. Also, the cable is in contact with the bottom tube for about 2 or 3 inches and it is scratching the frame. It looks like if the cable were routed through the entire cable guide, it would not be in contact with the frame. I think the cable should be threaded through the front part, through the gap in the middle and through the rear section of the cable guide. Am I wrong? Maybe this would help with the adjustment?

Last edited by Equinox; 03-19-09 at 07:36 AM. Reason: spelling
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Old 03-19-09, 07:53 AM
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Whoops, tandem.

BB cable guides are designed for single bikes. The bottom tube on a tandem routes the cable at a different angle relative to the bottom bracket. Without seeing your bike I'm guessing that your cable routing on the BB cable guide is correct.

Check out everyplace where you have a cable stop. Can you see a tiny wire or two sticking out? If you can, that's your problem. If the shift cable housing ends aren't capped properly, the housing will gradually shorten itself. When that happens, tune ups will improve the shifting for a period of time but the problem will keep coming back.

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Old 03-19-09, 09:27 AM
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Originally Posted by Retro Grouch View Post
Whoops, tandem.

BB cable guides are designed for single bikes. The bottom tube on a tandem routes the cable at a different angle relative to the bottom bracket. Without seeing your bike I'm guessing that your cable routing on the BB cable guide is correct.

Check out everyplace where you have a cable stop. Can you see a tiny wire or two sticking out? If you can, that's your problem. If the shift cable housing ends aren't capped properly, the housing will gradually shorten itself. When that happens, tune ups will improve the shifting for a period of time but the problem will keep coming back.
Could you elaborate on what a shift cable housing is? Is it where the barrel adjuster is?
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Old 03-19-09, 09:50 AM
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Originally Posted by Equinox View Post
Could you elaborate on what a shift cable housing is? Is it where the barrel adjuster is?
Yup. The shift cable housing is the flexible tube that the skinny cable runs through. It needs to have a plastic or metal cap at each end. Sometimes, however, even that doesn't do the job.
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Old 03-19-09, 11:37 AM
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Also, triples are notoriously difficult to adjust on bikes with normal-length cable runs. At least, I have a terrible time with them. Keep searching for the problem - I'm guessing new housing would help, but you might have just had that done.
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Old 03-19-09, 12:02 PM
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I dropped it off at the shop and I showed the technician how the cable was routed through the brazed-on guide under the bottom bracket, and he said it was wrong and the cable should not be in contact with the frame. I assume he assembled the bike. He looked perplexed, and I think he thinks that I did it, but I did not STG.
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Old 03-20-09, 06:26 AM
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My LBS is wonderful. The technician replaced the front derailleur cable and admitted it was not routed correctly through the brazed-on cable guide tube. He apologized because he said he should have caught it earlier. I know this may not be the cause of the problem, but at least a problem is fixed. He told me I will get cable stretch with the new cable, but I can deal with that.
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