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Interesting mechanical; resolved, but worth sharing.

SecteurSecteur Posts: 1,971
edited January 2017 in Workshop
Hello,

I am a pretty handy self taught home bike mechanic - much trial and error, mistakes and injured fingers - but there's not much I can't fix on my bike these days. This place has been an amazing resource and helped me out of many a mechanical conundrum, so I thought I'd post this.

A year ago, a workshop replaced my rear derailleur. They were doing some other more specialised work I wasn't capable of doing myself, so although it's something I'd normally do myself I asked them to do it whilst they had my bike.

On collecting the bike, they mentioned they had shortened the loop of cable between the bike frame and the rear derailleur, as it was apparently too long. I thought nothing of it.

Fast forwards to today, when I had the *third* identical mid-ride mechanical since that work was done (never happened before).

6zargx.jpg

As you can see, the rear derailleur cable becomes frayed meaning that I lose all my rear gears as the cable is no longer able to shift through the small hole of the derailleur housing. It is fraying from the left, not where the bolt is on the right. The loose cable ends are retracting back from where they are severed on the left, and bunching up towards the bolt on the right.

The last two times it snapped completely - a terminal event where I ride, due to the hills - and a taxi ride home.

Today I got home as there was enough cable left to hold a static gear, and I simply didn't shift the whole way - luckily at the roadside I could position and hold the rear derailleur almost half way up the cassette (5 out of 11 up the block) but living in the West Pennines let me tell you I had a very lumpy grind of a ride home!

ANYWAY, back to the problem - the last 2 times the cable was replaced after this failure, it wasn't clear what the exact cause was, but today I stripped everything back and below is the rear derailleur cable outer (fresh gear cable in situ just for the photograph), where it had been shortened by the mechanic last year, and also proven (by measuring and observing) to be the exact point at which the cable was fraying. Look how far back the plastic cover was stripped, and on close observation the (now rusted) metal part was sharp, uneven and jagged.

73f7fq.jpg

So, remember when reading about cutting cable outers, how the books always say to cut cleanly and to file the metal smooth and flat - well, this is a prime example of how important doing this is.

I hope this post helps someone remember to do this the next time they change the cables / outers, and so prevents a similar problem.
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Posts

  • jgsijgsi Posts: 5,029
    If you had bought the best (sadly expensive) cycle specific cable cutters, you wouldnt have had any of this mither.
    You just cannot use ordinary pliers.
  • SecteurSecteur Posts: 1,971
    edited August 2016
    Thanks for your contribution, but if you re-read you'll see that it was the workshop that cut the cable, not me!

    I would NEVER cut a cable and leave it as poorly prepared as that.

    Perhaps I didn't make it clear enough, but what you say is exactly my point - it's worth doing it properly.

    I do have the Park tools ones (expensive), and they give a beautiful clean cut which I then open out with a small probe inserted into the housing, and then file the cut end flat and smooth. Perfect every time.
  • SecteurSecteur Posts: 1,971
    Oh, and I've said this before - I have had problems with every single workshop I have used, and just no longer trust the standard of work, which is a major driving force in my investment in all the Park tools and time learning to do it all myself.

    I believe there are great mechanics out these, but of the 5 I have used over the years, every single time without exception I have come away with problems.

    The best possible investment is in tools and in yourself learning to do it all yourself.

    I have the time and the willingness to invest in getting my repairs absolutely perfect - a mechanic is working to time with a big workload, so there will always be problems, it seems.

    Apologies to any professional mechanics here.
  • dodgydodgy Posts: 2,890
    JGSI wrote:
    If you had bought the best (sadly expensive) cycle specific cable cutters, you wouldnt have had any of this mither.
    You just cannot use ordinary pliers.

    That is the wrong jacket and trousers.
  • joe2008joe2008 Posts: 1,531
    JGSI wrote:
    If you had bought the best (sadly expensive) cycle specific cable cutters, you wouldnt have had any of this mither.
    You just cannot use ordinary pliers.

    Nice. If you're going to reply at least have the courtesy to read the opening post.
  • keef66keef66 Posts: 13,123
    I too like doing all my own fettling. Unlike some bike shops I can take as long as necessary in order to achieve a perfect result. For squaring the cut ends of cable outer I like using a Dremel with a grinding disc; showers of sparks and a very clean, square finish.

    One tip for that final loop of cable before the derailleur; bend it to shape before finishing the ends (think Sheldon needs credit for that one...)

    And I've read that SRAM rear derailleurs like a longer loop anyway.
  • jgsijgsi Posts: 5,029
    joe2008 wrote:
    JGSI wrote:
    If you had bought the best (sadly expensive) cycle specific cable cutters, you wouldnt have had any of this mither.
    You just cannot use ordinary pliers.

    Nice. If you're going to reply at least have the courtesy to read the opening post.

    ha.. user error, plain and simple
    never trust anyone else on your own bike..and dont leave it a year before you actually look at what makes a bike tick
  • crankycrankcrankycrank Posts: 1,830
    keef66 wrote:
    I too like doing all my own fettling. Unlike some bike shops I can take as long as necessary in order to achieve a perfect result. For squaring the cut ends of cable outer I like using a Dremel with a grinding disc; showers of sparks and a very clean, square finish.

    One tip for that final loop of cable before the derailleur; bend it to shape before finishing the ends (think Sheldon needs credit for that one...)

    This^^. And it could be that the shop did cut the OP's cable housing properly but over time the ends can get chewed up and uneven sometimes.
  • keef66keef66 Posts: 13,123
    JGSI wrote:
    ha.. user error, plain and simple
    never trust anyone else on your own bike..and dont leave it a year before you actually look at what makes a bike tick

    If my bike's ticking then I have to take it to bits to make it stop. I have a chirruping front wheel that's currently annoying me. Once per revolution, and only when I'm on the bike. Nothing's rubbing anywhere. I've confirmed it's the wheel by swapping in another from the winter bike, which was silent (but brought to my attention a small rattle from my mini pump - doh!)

    I've so far oiled the nipples, cleaned / regreased / adjusted the bearings, QR lever and dropouts, removed and reinstalled tube and tyre, and put a bit of tape round the valve stem. Test ride tonight!
  • keef66keef66 Posts: 13,123
    And it could be that the shop did cut the OP's cable housing properly but over time the ends can get chewed up and uneven sometimes.

    That too. Had that on my winter bike. The outer running from the RH shifter to the stop on the downtube needed tidying up after a few years; the wire strands were poking out of the plastic casing pretty much like the OP's photo. Probably should have replaced the whole length, but I just chopped another half an inch off and tidied up the end with the Dremel again.

    I am a bit of a cheapskate, and CBA with disturbing the bar tape...
  • crankycrankcrankycrank Posts: 1,830
    keef66 wrote:
    I am a bit of a cheapskate, and CBA with disturbing the bar tape...
    Ha, me too. 8)
  • step83step83 Posts: 4,107
    keef66 wrote:
    And it could be that the shop did cut the OP's cable housing properly but over time the ends can get chewed up and uneven sometimes.

    That too. Had that on my winter bike. The outer running from the RH shifter to the stop on the downtube needed tidying up after a few years; the wire strands were poking out of the plastic casing pretty much like the OP's photo. Probably should have replaced the whole length, but I just chopped another half an inch off and tidied up the end with the Dremel again.

    I am a bit of a cheapskate, and CBA with disturbing the bar tape...

    Only joy of internal routing, you only need to replace that short bit of cable.

    Even with a proper cutter you sometimes need to finish the ends, as in reopen an face them off. Park tool cutters dont have this but my old set had a spike which you pressed into the cable hole re rounding the hole and if you look before doing it pushing the plastic inner sleeve back into place, quick run with a file an job done.

    Shop mechanics are time constrained, home mechanics are not :wink:

    Keef66, check the bearings may need a little love.
  • rolf_frolf_f Posts: 16,015
    Secteur wrote:
    The last two times it snapped completely - a terminal event where I ride, due to the hills - and a taxi ride home.

    One small precaution would have saved you the cab ride home. Tape a short length of gear cable to the underside of your saddle - one end should be knotted. If the gear cable breaks, you remove the end of the old cable from the mech (tie the loose end to the seat stay with the cable tie you also have under your saddle!) and thread the short cable through the back of the mech so the knot is next to the adjuster. Then clamp the other end to the cage in the normal way - by putting inward pressure on the mech you can align it with any gear you like. Takes moments, saves 10s of £s!
    Faster than a tent.......
  • dodgydodgy Posts: 2,890
    Or a much easier and tried and tested method. Use the limit adjuster screws on the rear mech to force the selection of a single gear.
  • Alex99Alex99 Posts: 1,407
    The second possibility is that shortening the loop of outer caused the problem. Still seems pretty amazing to me that a less than perfectly finished cable outer would cause cables to break so easily when the cable can still move freely prior to the breakage. Still, guess it doesn't cost a lot to look out for this.
  • jermasjermas Posts: 484
    Are you sure the cable routing around the clamp bolt is correct? If that's a 6800 gs the cable clamps underneath where it is now. It sure looks to me like it's the clamp that's causing the cable fray.
  • dodgydodgy Posts: 2,890
    Good spot jermas, you could be right there.
  • SecteurSecteur Posts: 1,971
    jermas wrote:
    Are you sure the cable routing around the clamp bolt is correct? If that's a 6800 gs the cable clamps underneath where it is now. It sure looks to me like it's the clamp that's causing the cable fray.

    As per OP, the fraying is 100% from the left - within the derailleur assembly - absolutely not where the bolt is. I appreciate the photo doesn't make it clear which is why I was very specific with the description in my OP.

    As for the cable fixing above/below the bolt, that was done (incorrectly) by a cannondale mechanic at the local workshop a month ago when it last frayed thru. When I fixed it myself yesterday, I clamped the cable exactly as described in the shimano literature - below - as it should be. Well spotted! I hadn't noticed until now.

    Yet ANOTHER example of shoddy mechanic work at the workshop!! This is EXACTLY what I have complained about time and time again on here. Well spotted. And this was a shimano / cannondale certified mechanic too. I am utterly fed up of these guys.

    In either case, the bolt itself isn't causing the fraying, though I now have to admit the incorrect clamping may have caused slightly more rubbing to occur at the sharp cable outer within the derailleur assembly which is *definitely* to the millimetre where the actual fraying is occurring.
  • SecteurSecteur Posts: 1,971
    PS and that's why threads like this are so useful for us to post! Excellent feedback & discussion.
  • SecteurSecteur Posts: 1,971
    Gosh that has really peeved me off (noticing the last mechanic bolted the cable wrong last month).

    Lately the majority of my infrequent posts here have been about how frustrated and disillusioned I have become with workshop mechanics.

    I have used 5 different ones over the years, and without exception I have come away with problems every single time I have had to take my bike in. They will fix, or attempt to fix, one problem and I get home and find other problems requiring time and effort which I thought I had just paid for (e.g. The first emergency cable repair I had to have done for the issue above replaced the cable but completely and utterly messed up both my front & rear derailleur settings meaning a delayed ride and a messy faff sorting them out - just one of many examples).

    Both times I bought my new bikes, they have come home with major noise problems, ultimately due to very basic things that weren't done (greasing dropouts etc) causing me heartache & grief and multiple return trips to the shop. And multiple distressed posts here where I thought the noise from my brand new bike was a dodgy BB when it turned out to be simply a bone dry dropout despite the PDI form having that box ticked as greased & checked. That one took 3 return trips, and the day they finally sorted 's been silent and perfect since. If I'd known then what I know now.

    I have lost all faith in these people, and as per previous posts I spent ££ on all the proper high quality tools and spent a long time learning how to do everything myself. And of course I have the time and motivation to really solve problems and carry out jobs to perfection. I feel bad for people who aren't inclined to do it themselves and are at the mercy of these people as I used to be.

    I try to be fair and not tar every mechanic with the same brush, because clearly there are good guys out there, but I have never found one and am really fed up of the poor attitude and poor quality of work.

    Bah! Rant over!
  • jermasjermas Posts: 484
    Gear changes (indexing) should be better too with the cable correctly fitted.
  • SecteurSecteur Posts: 1,971
    Yes I have done one ride since I fixed it all myself (yesterday) and it was indexing perfectly.

    Normally I need to make a minor tweak but I somehow managed to get it spot on first time (more through luck than skill, I'm sure!)

    Still, well spotted! Sorry it precipitated that rant though!
  • Alex99Alex99 Posts: 1,407
    Secteur wrote:
    jermas wrote:
    Are you sure the cable routing around the clamp bolt is correct? If that's a 6800 gs the cable clamps underneath where it is now. It sure looks to me like it's the clamp that's causing the cable fray.

    As per OP, the fraying is 100% from the left - within the derailleur assembly - absolutely not where the bolt is. I appreciate the photo doesn't make it clear which is why I was very specific with the description in my OP.

    As for the cable fixing above/below the bolt, that was done (incorrectly) by a cannondale mechanic at the local workshop a month ago when it last frayed thru. When I fixed it myself yesterday, I clamped the cable exactly as described in the shimano literature - below - as it should be. Well spotted! I hadn't noticed until now.

    Yet ANOTHER example of shoddy mechanic work at the workshop!! This is EXACTLY what I have complained about time and time again on here. Well spotted. And this was a shimano / cannondale certified mechanic too. I am utterly fed up of these guys.

    In either case, the bolt itself isn't causing the fraying, though I now have to admit the incorrect clamping may have caused slightly more rubbing to occur at the sharp cable outer within the derailleur assembly which is *definitely* to the millimetre where the actual fraying is occurring.

    Whilst it is clear that the fraying is to the left, does the wrong clamp position put the cable through a more extreme bend?
  • SecteurSecteur Posts: 1,971
    Alex99 wrote:
    Secteur wrote:

    In either case, the bolt itself isn't causing the fraying, though I now have to admit the incorrect clamping may have caused slightly more rubbing to occur at the sharp cable outer within the derailleur assembly which is *definitely* to the millimetre where the actual fraying is occurring.

    Whilst it is clear that the fraying is to the left, does the wrong clamp position put the cable through a more extreme bend?

    Think I just said that! You may or may not be right, I honestly don't know. I am fairly certain (but not 100%) that the two times before this latest fix, it was bolted correctly as I checked myself. Somehow, I didn't spot it incorrectly bolted this last time. In any case, my original advice to ensure the cable outers are well finished still stands.
  • Alex99Alex99 Posts: 1,407
    Secteur wrote:
    Alex99 wrote:
    Secteur wrote:

    In either case, the bolt itself isn't causing the fraying, though I now have to admit the incorrect clamping may have caused slightly more rubbing to occur at the sharp cable outer within the derailleur assembly which is *definitely* to the millimetre where the actual fraying is occurring.

    Whilst it is clear that the fraying is to the left, does the wrong clamp position put the cable through a more extreme bend?

    Think I just said that! You may or may not be right, I honestly don't know. I am fairly certain (but not 100%) that the two times before this latest fix, it was bolted correctly as I checked myself. Somehow, I didn't spot it incorrectly bolted this last time. In any case, my original advice to ensure the cable outers are well finished still stands.

    No argument
  • keef66keef66 Posts: 13,123
    keef66 wrote:
    JGSI wrote:
    ha.. user error, plain and simple
    never trust anyone else on your own bike..and dont leave it a year before you actually look at what makes a bike tick

    If my bike's ticking then I have to take it to bits to make it stop. I have a chirruping front wheel that's currently annoying me. Once per revolution, and only when I'm on the bike. Nothing's rubbing anywhere. I've confirmed it's the wheel by swapping in another from the winter bike, which was silent (but brought to my attention a small rattle from my mini pump - doh!)

    I've so far oiled the nipples, cleaned / regreased / adjusted the bearings, QR lever and dropouts, removed and reinstalled tube and tyre, and put a bit of tape round the valve stem. Test ride tonight!

    Test ride last night; glorious silence from the front wheel. Unfortunately I don't know which of my fixes worked! Still need to silence the mini pump. And possibly the batteries in the front light. Anyone know if rechargeable AA batteries are fatter when fully charged or if that's just my imagination?
  • SecteurSecteur Posts: 1,971
    Just thought I'd update this thread to say that since sorting the outer out, I've not had any recurrence and have done a lot of miles since - they cable looks as new.
  • keef66keef66 Posts: 13,123
    Secteur wrote:
    Just thought I'd update this thread to say that since sorting the outer out, I've not had any recurrence and have done a lot of miles since - they cable looks as new.

    Excellent!

    One thing I have observed with cut ends of gear cables is that even if the outer is cleanly cut and finished, sometimes over time the steel strands do start to work their way out of the plastic outer casing. I suspect it depends on the type of ferrule fitted (if any) and the shape / size of the cable stop or housing it's going in to.

    The length of gear outer from my RH shifter to the downtube stop / barrel adjuster has done this twice, Each time the end looked like your photo; the exposed strands starting to rust, and so producing cable drag.

    Both times I've just snipped off an extra cm or so and refinished the cut end, but I think I really should replace the thing.
  • Godders1Godders1 Posts: 750
    Yup I've fitted cables using decent cutters and have finished the ends so they're nice and neat and when I've gone to change them a year or so later they look just like in the OP pic. Like you say the outer seems to recede somehow over time.
  • rolf_frolf_f Posts: 16,015
    Rolf F wrote:
    Secteur wrote:
    The last two times it snapped completely - a terminal event where I ride, due to the hills - and a taxi ride home.

    One small precaution would have saved you the cab ride home. Tape a short length of gear cable to the underside of your saddle - one end should be knotted. If the gear cable breaks, you remove the end of the old cable from the mech (tie the loose end to the seat stay with the cable tie you also have under your saddle!) and thread the short cable through the back of the mech so the knot is next to the adjuster. Then clamp the other end to the cage in the normal way - by putting inward pressure on the mech you can align it with any gear you like. Takes moments, saves 10s of £s!
    dodgy wrote:
    Or a much easier and tried and tested method. Use the limit adjuster screws on the rear mech to force the selection of a single gear.

    Didn't spot this at the time but might as well respond now. No - this isn't a much easier method - quite the reverse infact! You can't get the limit screws to shift more than a couple of gears at the most - I know, I've tried it. The piece of gear cable gives you the option of any gear and is probably no harder to set up. The limit adjuster might work well enough on the plain of York but if you are the wrong side of Hardknott (or many lesser hills in between), the bit of gear cable is the thing that will save your ride (unless you can do that sort of climb on 34-14).
    Faster than a tent.......
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