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  1. #1
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    Cable stretch syndrome

    Think I値l be placing an order soon.
    Are all rear derailer cables about the same as far out of the box stretch goes or do some stretch less than others for a 9 speed.

    Thanks

  2. #2
    MTJ
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    All cables stretch . . .

    Since the cable is just a bunch of wound steel fibers, those fibers will effectively "unwind" as they get used. This happens to all cables; always has, always will. Generally speaking, though, the cables will stretch slightly after a few rides (just enough to totally screw up your shifting) and then will not stretch after that.

    So no matter what cables you get, they will stretch. Readjust and keep riding.

    I can't help but ownder if there's not more to your question though. If you're trying to get crisper, more accurate shifts, the cable housing makes a big difference. If you ride in crappy conditions, a sealed system makes a huge difference. I like Avid Flak Jackets, they're not super expensive and work very well.

  3. #3
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    Thanks for your reply

    Just trying to eliminate a step caused by cable stretch that痴 all, not that I知 inexperienced in biking and repair but rather uniformed about what痴 available on the market.

  4. #4
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    Most quality cables will not change significantly enough if at all throughout their useful life for it to be much of an issue. Housing/ferrules also compress and can shrink which can give the perception of cable stretch. Most initial cable stretch during the first few weeks of a new housing and cable installation is actually the housing and ferrules compressing into position. Make sure to give the cables a good solid tug once everything is bolted down to compress everything and seat it into place, then release the cables from the derailleur, retighten the slack and adjust properly.

  5. #5
    Chrome Toaster
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    Quote Originally Posted by MTJ
    Since the cable is just a bunch of wound steel fibers, those fibers will effectively "unwind" as they get used. This happens to all cables; always has, always will. Generally speaking, though, the cables will stretch slightly after a few rides (just enough to totally screw up your shifting) and then will not stretch after that.

    So no matter what cables you get, they will stretch. Readjust and keep riding.
    What you are refering to has nothing to do with cable stretch. New cables throw your shifting out of what when new if you did not "pre-compress" the housing into place. Once all the housing is fully bottomed out inside the ferrules shifting will not change.

  6. #6
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    Quote Originally Posted by Hecubus
    Most quality cables will not change significantly enough if at all throughout their useful life for it to be much of an issue. Housing/ferrules also compress and can shrink which can give the perception of cable stretch. Most initial cable stretch during the first few weeks of a new housing and cable installation is actually the housing and ferrules compressing into position. Make sure to give the cables a good solid tug once everything is bolted down to compress everything and seat it into place, then release the cables from the derailleur, retighten the slack and adjust properly.
    Agreed.

    When housing ends are squared off (what most people do) the housing does not sit all the way in the bottom of the ferrule (there are some exceptions - like when using 4mm housing with ferrules meant for 5mm housing). Over time, the cable housing will try to force itself against the bottom of the ferrule. As the housing squeezes down into the ferrule, the length between the terminating ferrules is getting shorter. When the cable run gets shorter, the effective length of the cable gets longer and this is what people typically call cable stretch. The cable is not getting longer - the cable run (housing + ferrules) is getting shorter.

    I drew a crude picture below to help illustrate the issue. All ferrules will have some sort of inside radius at the end. If you just cut the end square, the end can't contact the bottom of ferrule until the casing material is compressed to allow the housing to squeeze into the bottom. I've outlined the trouble area in Figure A. To avoid this, I bevel the end of my cables as shown in Figure B. I like to hear an audible noise of metal hitting metal when I slide the housing into the ferrule so I can verify the metal winding/wire inside the housing has hit the bottom of the ferrule. If you find yourself squeezing the housing into the ferrule and wondering if it is bottomed - trust me, it's not. I've done this trick for years and I can basically recable my bike, adjust everything, and not touch it again for another year until it's time to change cables.
    Attached Images Attached Images
    Last edited by steiny; 07-03-2006 at 08:58 PM.

  7. #7
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    Exacty my point. Sealed plastic sealed cable ends are also harder to seat because they have a very snug fit. Its really difficult to push them in all the way by hand even if it feels like they are all the way in. The rubber sealing at the ends compresses to a certain point too. The cable tug method has always worked fine for me. Clamp the cable on the derailleur after installing the cables, shift to the last gear (big cog for rapid rise, small for high normal) and grab the cable from one of the exposed runs and pull it gently and firmly. You can feel the housing pressing into place. The cable will be totally slack by then and you need to reclamp it again. I've never had to readjust after that. This is the problem a lot of people complain about when they say they recable and readjust everything and even then they can't get stuff to work right. It goes out of adjustment over the course of a few rides. Then they get pissed and spend money on new parts. By then the housing is fully compressed and the perception the problem was solved comes in.

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