I'm stumped: fixed it but not sure how
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  1. #1
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    I'm stumped: fixed it but not sure how

    I have a steel Mondonico with a 2018 Campy Potenza group. Started out on a ride yesterday and all is well. About 4 miles in, the rear derailleur will no longer shift to the smallest 3 or 4 cogs. I can shift with the inner lever to bigger cogs, but the action is very light. If I keep depressing the thumb button, the cable goes completely slack but the derailleur never moves to the smaller cogs. So, I am thinking busted spring on the derailleur. Today I remove the rear wheel and move the derailleur with my hand. There is spring tension across the whole range and shifting is working fine. I put the wheel back on and everything is fine again. I take it for a short spin, and its all working again. I don't like this as now I am afraid to use this bike thinking it may reoccur. Any theories and things to try?

  2. #2
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    Sounds like the cable is binding somewhere. I'd start with the casing and ferrules from the RD and work towards the shifter. Make sure the casing entering the shifter is not bent in any way and the plastic outer casting is properly trimmed. There should be about 1mm of the steel casting strands showing at the end. Also check the casing lining and make sure it's not rubbing on the cable itself.

  3. #3
    'brifter' is a lame word.
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    Quote Originally Posted by nova_rider View Post
    Sounds like the cable is binding somewhere. I'd start with the casing and ferrules from the RD and work towards the shifter. Make sure the casing entering the shifter is not bent in any way and the plastic outer casting is properly trimmed. There should be about 1mm of the steel casting strands showing at the end. Also check the casing lining and make sure it's not rubbing on the cable itself.
    How'd you come up w/ this?
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  4. #4
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    Quote Originally Posted by cxwrench View Post
    How'd you come up w/ this?
    Campy cables come packaged this way to ensure properly seating. If trimmed, it should be prepped as such.

  5. #5
    Russian Troll Farmer
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    I'm wondering if you picked up a mall twig inside your derailleur mechanism.
    "L'enfer, c'est les autres"

  6. #6
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    Quote Originally Posted by nova_rider View Post
    Campy cables come packaged this way to ensure properly seating. If trimmed, it should be prepped as such.
    I have never seen that in the Campy instructions, could you provide a link to the part that says you should do this? All I'm seeing is "Cut the housing to a suitable length and fit a housing end". I've been doing this a loooong time and have never seen anything saying to leave 1mm of strands protruding from the housing.

    ETA: I can't even imagine how you'd do this reliably and repeatably.
    Last edited by cxwrench; 2 Weeks Ago at 04:49 PM.
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  7. #7
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    Quote Originally Posted by No Time Toulouse View Post
    I'm wondering if you picked up a mall twig inside your derailleur mechanism.
    Maybe. I can't reproduce the original problem. The cables are clean and sliding through the casing without any binding. Perhaps something was jammed in there that fell out. It's shifting fine now but I am a bit apprehensive of taking this bike on a long ride now

  8. #8
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    Quote Originally Posted by cxwrench View Post
    I have never seen that in the Campy instructions, could you provide a link to the part that says you should do this? All I'm seeing is "Cut the housing to a suitable length and fit a housing end". I've been doing this a loooong time and have never seen anything saying to leave 1mm of strands protruding from the housing.

    ETA: I can't even imagine how you'd do this reliably and repeatably.
    There are no Campy instructions on this. I just noticed this on all their new cable housings and started doing it myself. The casing end that goes into the shifter body does not use a ferrule, so having a perpendicular casing end matters in providing good shifter feel and response. Trimming the outer casing is just another way to ensure nothing can get in the way.

  9. #9
    'brifter' is a lame word.
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    Quote Originally Posted by nova_rider View Post
    There are no Campy instructions on this. I just noticed this on all their new cable housings and started doing it myself. The casing end that goes into the shifter body does not use a ferrule, so having a perpendicular casing end matters in providing good shifter feel and response. Trimming the outer casing is just another way to ensure nothing can get in the way.
    No wonder I've never seen this, it's just your idea of what works. I've not once seen nor heard of anyone doing this and at one point I even worked for a pro team that rode Campy. It's definitely not a necessary step. Cut the housing square and put on a ferrule. Done. Unless it's the end going into the shifter as you posted.
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  10. #10
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    Quote Originally Posted by cxwrench View Post
    No wonder I've never seen this, it's just your idea of what works. I've not once seen nor heard of anyone doing this and at one point I even worked for a pro team that rode Campy. It's definitely not a necessary step. Cut the housing square and put on a ferrule. Done. Unless it's the end going into the shifter as you posted.
    I have never done this or heard of this either My guess is that its just the way the casings are cut during manufacturing, rather than a conscious effort.

  11. #11
    'brifter' is a lame word.
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    Quote Originally Posted by DaveG View Post
    I have never done this or heard of this either My guess is that its just the way the casings are cut during manufacturing, rather than a conscious effort.
    Exactly what I'm thinking. As I added to post 7 there isn't really any way for a mechanic to do this reliably or repeatedly.
    As for your problem I'm going w/ something (rock/stick) got temporarily stuck in your derailleur somewhere and limited travel. Can't really think of anything else that would cause it as you seem to have eliminated the other possible causes.
    I work for some bike racers
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    and a bunch of skateboards

  12. #12
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    Quote Originally Posted by DaveG View Post
    I have never done this or heard of this either My guess is that its just the way the casings are cut during manufacturing, rather than a conscious effort.
    If anything, leaving the inner wires of the housing exposed like that will make a bunch of noise when the grind against the inside of the shifter or ferrule. They will also be more likely to fray or crumble under pressure, causing poor shift quality. It just doesn't make any sense to me and I would strongly recommend against it.

  13. #13
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    Quote Originally Posted by cxwrench View Post
    Exactly what I'm thinking. As I added to post 7 there isn't really any way for a mechanic to do this reliably or repeatedly.
    As for your problem I'm going w/ something (rock/stick) got temporarily stuck in your derailleur somewhere and limited travel. Can't really think of anything else that would cause it as you seem to have eliminated the other possible causes.
    I went for a ride this morning with that bike. Shifting was better than before, in that the shifts to bigger cogs required less effort. Perhaps there was something jammed in there for a while

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