Name of a part so I can find a spare

slowbike
slowbike Posts: 8,498
edited July 2016 in Workshop
On my Tarmac there's a cable guide under the bottom bracket - being an old(er) bike I think it's become worn - shifting down needs more clicks than shifting up - replaced all the cables & outers so this is the last bit ...

I'd like to find a replacement - is it just called a cable guide? or is there another name for it?

Comments

  • keef66
    keef66 Posts: 13,123
    Bottom bracket cable guide?
  • slowbike
    slowbike Posts: 8,498
    yer ... it's as simple as cable guide - problem is the names are too generic and the online stores search systems too crap to be able to return meaningful results ... oh well - I've emailed one of my local bike shops that deals with Specialized ..
  • timothyw
    timothyw Posts: 2,482
    I'd have though it's more likely that the rear derailleur has lost some of it's spring with age - might be time for an overhaul:
    http://www.parktool.com/blog/repair-hel ... r-overhaul

    Or a new rear derailleur if you're feeling flush....
  • imposter2.0
    imposter2.0 Posts: 12,028
    I don't see any reason why the cable guide would be causing such an issue - and as long as the cable runs smoothly through it, there will be nothing wrong with it. I would look elsewhere...
  • slowbike
    slowbike Posts: 8,498
    The reason I suspect the cable guide is because when I click down on the shifter the tension in the cable above the bb is low whilst the tension behind it is still quite high.
    There must be friction in the cable guide - whether that was there before this issue or not I don't know.

    Thanks for the link to the mech overhaul - I'll have to have a look... thankfully it's not vital - I can still ride the bike!
  • lesfirth
    lesfirth Posts: 1,382
    Slowbike wrote:
    The reason I suspect the cable guide is because when I click down on the shifter the tension in the cable above the bb is low whilst the tension behind it is still quite high.
    There must be friction in the cable guide - whether that was there before this issue or not I don't know.

    Thanks for the link to the mech overhaul - I'll have to have a look... thankfully it's not vital - I can still ride the bike!
    I have had the same problem with a front mech cable. The cable had worn a groove in the guide and was ticking in the groove. A new guide solved the problem.
  • keef66
    keef66 Posts: 13,123
    Slowbike wrote:
    The reason I suspect the cable guide is because when I click down on the shifter the tension in the cable above the bb is low whilst the tension behind it is still quite high.
    There must be friction in the cable guide - whether that was there before this issue or not I don't know.

    Thanks for the link to the mech overhaul - I'll have to have a look... thankfully it's not vital - I can still ride the bike!

    Given the symptoms you describe, I cannot fault your logic. I can imagine a cable wearing a narrow groove in a plastic component and becoming draggy. Does it still do it if you slap a load of grease on the cable / guide? Is it possible the new cable is fractionally thicker than the previous one, and so exacerbating the issue?
  • keef66
    keef66 Posts: 13,123
    Could you take off the guide, thoroughly degrease it, and fill in the worn groove with superglue? Might not last long, but it would tell you if the guide is to blame
  • slowbike
    slowbike Posts: 8,498
    keef66 wrote:
    Slowbike wrote:
    The reason I suspect the cable guide is because when I click down on the shifter the tension in the cable above the bb is low whilst the tension behind it is still quite high.
    There must be friction in the cable guide - whether that was there before this issue or not I don't know.

    Thanks for the link to the mech overhaul - I'll have to have a look... thankfully it's not vital - I can still ride the bike!

    Given the symptoms you describe, I cannot fault your logic. I can imagine a cable wearing a narrow groove in a plastic component and becoming draggy. Does it still do it if you slap a load of grease on the cable / guide? Is it possible the new cable is fractionally thicker than the previous one, and so exacerbating the issue?
    keef66 wrote:
    Could you take off the guide, thoroughly degrease it, and fill in the worn groove with superglue? Might not last long, but it would tell you if the guide is to blame

    Thanks for the logic confirmation - my job is troubleshooting (not mech devices though) so I'm kinda used to thinking things through. I also have a fair amount of experience in control lines through dinghy racing - so again, used to trouble shooting when those don't work (usually seized or underspecced block) :)

    I'd considered - and still should do I suppose - using a short segment of cable outer fastened to the cable guide and route the cable through that - my concern on that as a long term "fix" would be that it would fill with crud pretty quickly and make it a whole lot worse!
    I could try the glue method - there's quite a bit of tension in a gear cable though so not sure it would be tough enough.
  • sungod
    sungod Posts: 17,336
    with powercordz it's normal to put a few cm of ptfe sleeving over the cable where it runs over the bb guide

    it may get dust/cack inside, but with the cable at minimum tension it's easy to slip the sleeving along to clear it out and wipe the cable clean every so often
    my bike - faster than god's and twice as shiny
  • keef66
    keef66 Posts: 13,123
    I was thinking that while you're waiting for a (model specific / eye-wateringly expensive?) part from Specialized you could cludge the repair with superglue just long enough to prove it's the cause of the problem?

    I share your reservations about the length of outer beneath the BB. It would have to run a significant way up the downtube if it's to avoid being filled with watery crap from the front wheel
  • Man Of Lard
    Man Of Lard Posts: 903
    However as a proof of fault, in a temporary capacity the idea is sound.
  • slowbike
    slowbike Posts: 8,498
    thanks chaps - collective thoughts are welcome :) looks like I've got to make some time for tinkering ... :)

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