Shimano shifter eats another rear cable.............. - Page 3
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  1. #51
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    I think you have to be careful when shifting to not use too much force on the shift lever when you are in first gear. Since there's no indicator to tell you what gear you're in, you can be in the low gear on the cassette and think you have more gears left. That puts a large load in the cable and shortens it's life. I've got five years of use in a Jagwire Road Elite sealed cable system on an Ultegra 10s triple system with lots of miles and the cables shift like new.

  2. #52
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    Quote Originally Posted by mfdemicco View Post
    I think you have to be careful when shifting to not use too much force on the shift lever when you are in first gear. Since there's no indicator to tell you what gear you're in, you can be in the low gear on the cassette and think you have more gears left. That puts a large load in the cable and shortens it's life. I've got five years of use in a Jagwire Road Elite sealed cable system on an Ultegra 10s triple system with lots of miles and the cables shift like new.
    As I said before, I never had a cable eating problem with my 5600 shifters. Granted if you leave them in there long enough, the problem will happen. But I don't think the cable wrap is quite as tight until the 5700/6700/7900 generation - the first under the handlebar cable routing.
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  3. #53
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    Quote Originally Posted by Lombard View Post
    As I said before, I never had a cable eating problem with my 5600 shifters. Granted if you leave them in there long enough, the problem will happen. But I don't think the cable wrap is quite as tight until the 5700/6700/7900 generation - the first under the handlebar cable routing.
    That's what I have, 6703 shifters.

  4. #54
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    Quote Originally Posted by mfdemicco View Post
    I think you have to be careful when shifting to not use too much force on the shift lever when you are in first gear. Since there's no indicator to tell you what gear you're in, you can be in the low gear on the cassette and think you have more gears left. That puts a large load in the cable and shortens it's life.
    Nope. It's not a force problem. It's a friction/wear problem.
    You'd break your lever before you ever broke the cable. And if it were a force problem the cable would break in random places on the bike. But it doesn't. It always breaks at the same spot, where it wraps around a tight radius inside the shifter.

    If you've ever seen what wire rope looks like when it breaks from too much force, it does not look like this.

    I've never experienced this low gear shift force phenomenon. When I'm out of gears, I stop pushing, I don't try and push it with extra force. And yet my cables would fray inside the shifter.
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  5. #55
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    Quote Originally Posted by mfdemicco View Post
    I think you have to be careful when shifting to not use too much force on the shift lever when you are in first gear. Since there's no indicator to tell you what gear you're in, you can be in the low gear on the cassette and think you have more gears left. That puts a large load in the cable and shortens it's life. I've got five years of use in a Jagwire Road Elite sealed cable system on an Ultegra 10s triple system with lots of miles and the cables shift like new.
    You can see from the picture he posted where they fray.

    Even is someone was dumb enough to continue pushing and with a lot of force when they run out of gear that extra force wouldn't really get to that part of the cable with the last gear.

    Ever snap a fishing line by yanking to hard? That's never going to happen in a place you already reeled on to the spool.

  6. #56
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    Shimano shifter eats another rear cable..............

    Quote Originally Posted by tlg View Post
    Nope. It's not a force problem. It's a friction/wear problem.
    You'd break your lever before you ever broke the cable. And if it were a force problem the cable would break in random places on the bike. But it doesn't. It always breaks at the same spot, where it wraps around a tight radius inside the shifter.

    If you've ever seen what wire rope looks like when it breaks from too much force, it does not look like this.

    I've never experienced this low gear shift force phenomenon. When I'm out of gears, I stop pushing, I don't try and push it with extra force. And yet my cables would fray inside the shifter.
    No way. It's a fatigue problem and force definitely affects fatigue life. No way a cable in a plastic liner is going to fray from wear or be subject to much friction. All shift cables will eventually fray but in 800 miles? Not on any bike I have.

  7. #57
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    Quote Originally Posted by mfdemicco View Post
    It's a fatigue problem and force definitely affects fatigue life. No way a cable in a plastic liner is going to fray from wear or be subject to much friction. .
    You clearly don't understand fatigue.
    You also clearly don't understand the problem. They fray in the shifters, not the liner. From the tight bend radius... IN the shifter.
    It miraculously doesn't occur anywhere else.

  8. #58
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    Quote Originally Posted by tlg View Post
    You clearly don't understand fatigue.
    You also clearly don't understand the problem. They fray in the shifters, not the liner. From the tight bend radius... IN the shifter.
    It miraculously doesn't occur anywhere else.
    Yes right, no liner, but it's still fatigue and not wear as you have stated. Also, cables break at the cable button too.

  9. #59
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    Quote Originally Posted by mfdemicco View Post
    Yes right, no liner, but it's still fatigue and not wear as you have stated. Also, cables break at the cable button too.
    Right. Which gets the lease stress when trying to get into an extra gear because the max amount of cable has already bee wound. If the stress from trying to ram into another gear was the cause as you suggest it wouldn't happen there as I tried to explain with the fishing line comparison.

  10. #60
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    Quote Originally Posted by mfdemicco View Post
    Yes right, no liner, but it's still fatigue and not wear as you have stated.
    Friction, wear, fatigue. But absolutely not from too much force.
    You really have no clue what you're talking about.
    Seriously... I'm an engineer. I design sh!t with wire rope.

    A tight bend radius causes increase friction and wear inside the wire bundles as they rub and bend on each other.

    Cooks Wire Rope Handbook
    If the rope operates over inadequate size sheaves, the severe bending stresses imposed will cause the wires to break from fatigue

    Another undesirable effect of small sheaves is accelerated wear of both rope and sheave groove


    Severe bending is a major cause of short rope life. By contrast the larger the s heave diameter the less wear on the rope and the greater its strength efficiency


    Also, cables break at the cable button too.
    Maybe. But I've never seen it. I have had or seen cables fray IN shimano shifters about 50 times.
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  11. #61
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    Quote Originally Posted by tlg View Post
    Friction, wear, fatigue. But absolutely not from too much force.
    You really have no clue what you're talking about.
    Seriously... I'm an engineer. I design sh!t with wire rope.

    A tight bend radius causes increase friction and wear inside the wire bundles as they rub and bend on each other.

    Cooks Wire Rope Handbook
    If the rope operates over inadequate size sheaves, the severe bending stresses imposed will cause the wires to break from fatigue

    Another undesirable effect of small sheaves is accelerated wear of both rope and sheave groove


    Severe bending is a major cause of short rope life. By contrast the larger the s heave diameter the less wear on the rope and the greater its strength efficiency


    Maybe. But I've never seen it. I have had or seen cables fray IN shimano shifters about 50 times.
    You're saying that tension on the cable has no effect on the fatigue life of the cable? Then where are the stresses coming from? I agree that repeated bending of the cable over a small sheave is the real problem, but cable tension plays a part. I really don't want to get into a pissing contest here.

  12. #62
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    Shimano shifter eats another rear cable..............

    Tig, here are two pages from my Mechanical Engineering Design text by Shigley. See the fatigue graph and the two equations for p and Su. F = tensile force on rope.


  13. #63
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    mfd, think about this, how much stress is that cable being subject to, the return spring of the RD, that's it, that's nothing. It is internal of the cable stress, not from overall fatigue/stress.
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  14. #64
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    Quote Originally Posted by mfdemicco View Post
    You're saying that tension on the cable has no effect on the fatigue life of the cable? Then where are the stresses coming from? I agree that repeated bending of the cable over a small sheave is the real problem, but cable tension plays a part. .
    The stresses are coming from repeated bending over a small radius. This is a known issue.
    If designed property, tension is not an issue.
    If tension was the issue, you'd see fraying elsewhere, yet that never happens. It's always... Always at the same spot on the tight bend instead the shifter.
    If tension were the issue you'd see similar issues with sram or Campy. They don't ever have this issue.

  15. #65
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    Quote Originally Posted by tlg View Post
    The stresses are coming from repeated bending over a small radius.
    This I would agree with as the probable cause of most failure from an engineering stand point, however the spool has the tightest radius of any point on the cable's path not the radius turning into the shifter which most people point to as the cause of failure from a design point, not the spool. If Sram and Campy cables last so much longer, how are they taking up cable inside the shifter if not on a spool or are their spools larger diameter? (I'm not familiar with either, only own Shimano)
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  16. #66
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    Quote Originally Posted by duriel View Post
    mfd, think about this, how much stress is that cable being subject to, the return spring of the RD, that's it, that's nothing. It is internal of the cable stress, not from overall fatigue/stress.
    Not when you force the shifter when it's in first gear up against the cable stop. There a lot of force generated there and do it enough times you are going to shorten the fatigue life of the cable, perhaps dramatically, I don't know. I just read an article about this recently, but can't seem to find it now. I'll post a link when I do.

    And Tig, how do you explain 5 years of use and many miles I have on my Jagwire cables on 6703 shifters and they're still good? I'm not seeing a problem here. All cables eventually fray. I have a couple of bikes with the external STI shifters cables, and these cables fray too, except they do it at the cable button. I had cables fray at the button on bar end shifters too.

  17. #67
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    The cable can handle 65,000lbs per square inch, or so.... Your pushing on a 4" handle with your finger, YOU AIN'T ANYWHERE CLOSE TO 65,000#/IN2. PERIOD!
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  18. #68
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    Quote Originally Posted by duriel View Post
    The cable can handle 65,000lbs per square inch, or so.... Your pushing on a 4" handle with your finger, YOU AIN'T ANYWHERE CLOSE TO 65,000#/IN2. PERIOD!
    Not relevant. We're talking about fatigue failure and maybe wear of the cable, which occurs over a period of time where the cable is repeatedly bent over a small diameter sheave at a fraction of the tensile strength of the cable.

  19. #69
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    That was your whole arguement, now your changing what you position is? double?

    Do you understand what words mean? I'm out!
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  20. #70
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    Quote Originally Posted by mfdemicco View Post
    Not when you force the shifter when it's in first gear up against the cable stop. There a lot of force generated there and do it enough times you are going to shorten the fatigue life of the cable, perhaps dramatically, I don't know.
    A lot of force? Man, you are rough.
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  21. #71
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    Quote Originally Posted by tlg View Post
    Nope. It's not a force problem. It's a friction/wear problem.
    You'd break your lever before you ever broke the cable. And if it were a force problem the cable would break in random places on the bike. But it doesn't. It always breaks at the same spot, where it wraps around a tight radius inside the shifter.

    If you've ever seen what wire rope looks like when it breaks from too much force, it does not look like this.

    I've never experienced this low gear shift force phenomenon. When I'm out of gears, I stop pushing, I don't try and push it with extra force. And yet my cables would fray inside the shifter.
    Totally agree. And the cable will fatigue and start to fray whether or not it's in a liner. tlg is correct, it's the number of times the cable wraps and unwraps around...whatever they call it...the 'shift drum'? It's not the friction or force, it's the repetitive wrapping/unwrapping that causes the fatigue/fraying.
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    I am interested to hear more about this NOT being a problem with SRAM or Campagnolo?

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    Quote Originally Posted by Lombard View Post
    A lot of force? Man, you are rough.
    Let's look at that. 4" lever arm x 10 lbs force = 40 in lbs torque = 0.5" spool radius x 80 lbs cable tension vs. what, about 2 lbs derailleur spring force? 80 lbs cable tension vs 2. So yeah, I believe that many repeated shifts and false shifts into the first gear cable stop is contributing to shortening the fatigue life of the cable. See the formulas from the Shigley text I quoted above.

    Is the spool size smaller in STI shifters than in downtube or barcon shifters? I don't know. These older shifters don't seem to have issues with breaking cables. The lever arm is smaller. Barcons are about 1" and you know what gear you're in too.

    Are Campy or SRAM integrated shifters any better with respect to breaking cables? I don't know if they are or not, and if they are, what makes them better?

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    Quote Originally Posted by mfdemicco View Post
    Then where are the stresses coming from? I agree that repeated bending of the cable over a small sheave is the real problem,
    Not sure why you'd continue to argue after essentially not agreeing with your self either.
    Or why you continue to ignore the fact I have pointed out that the area that frays does not get most of stress from tying to get into a gear that's not there because it's already wound on to the spool.

  25. #75
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    Quote Originally Posted by Srode View Post
    This I would agree with as the probable cause of most failure from an engineering stand point, however the spool has the tightest radius of any point on the cable's path not the radius turning into the shifter which most people point to as the cause of failure from a design point, not the spool. If Sram and Campy cables last so much longer, how are they taking up cable inside the shifter if not on a spool or are their spools larger diameter?
    There is no 'spool'. It's not like a winch wrapping cable around a spool. The total cable pull on a shifter is only about ½”. It’s not wrapping anything. It’s just pulled on a cam. That cam is not the tightest bend. The tightest bend is in the shifter, where it’s sliding over a tight bend.

    Quote Originally Posted by mfdemicco View Post
    Not when you force the shifter when it's in first gear up against the cable stop. There a lot of force generated there and do it enough times you are going to shorten the fatigue life of the cable .
    For Christ sake, no one is doing that. That’s insane. Who is dumb enough to force their shifter when it reaches the end?

    Quote Originally Posted by mfdemicco View Post
    Not relevant. We're talking about fatigue failure and maybe wear of the cable, which occurs over a period of time where the cable is repeatedly bent over a small diameter sheave at a fraction of the tensile strength of the cable.
    lmao… now it’s a fraction of the tensile strength. But but but…. Excessive force is the issue?

    Quote Originally Posted by mfdemicco View Post
    Let's look at that. 4" lever arm x 10 lbs force = 40 in lbs torque = 0.5" spool radius x 80 lbs cable tension vs. what, about 2 lbs derailleur spring force? 80 lbs cable tension vs 2.
    Does your foot hurt from shooting yourself in it. If the derailleur spring is 2lbs, it doesn’t matter how much ‘torque’ you put into the shifter. The tension on the cable is…. 2lbs.

    Even given your ridiculous false shift theory, which no sane person would be doing, you have 80lbs of tension in the cable. The minimum breaking load on a 1.2mm 1 × 19 stainless steel wire rope is 270lbs. You ain't anywhere near that.
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