front mech indent too high?

matt21
matt21 Posts: 71
edited September 2013 in Workshop
Hi All

My front mech (triple) wont shift from middle to inner except if up the top of the cassette. Seemingly the chain is running under the contoured indent of the mech so it's not being pushed off. The derailleur is as far down the tube as is possible.
Any ideas anyone please?

Comments

  • sungod
    sungod Posts: 16,554
    sounds like the front mech just needs correctly fitting/adjusting

    find out which make+model, look on manufacturer's website for instructions, follow

    for instance... http://techdocs.shimano.com
    my bike - faster than god's and twice as shiny
  • matt21
    matt21 Posts: 71
    Hi and thanks. It's a 105 5703 and is fitted correctly. Low limit stop is fully released and the bb has a spacer fitted to move it out from the shell.
  • matt21
    matt21 Posts: 71
    Perhaps I should have added, It's a 30/39/52 triple on a tandem. The outer plate of the cage just passes the outer chainring and the mech blurb says it's fine for a 52 ring.
  • matt21
    matt21 Posts: 71
    Not to just talk to myself but just wondering if it could be that the angle between chainstay and seatube is too great. If so, can anyone suggest a way round it?
  • pdw
    pdw Posts: 315
    Is the mech definitely hitting the stop? Is there still some tension in the cable or is the mech stiff?
  • matt21
    matt21 Posts: 71
    Yep , the mech hits the stop and moves freely. I've just measured the angle though between chainstay and seatpost and it looks like it's around 76 degrees. Could it be that the rear triangle isn't acute enough?
  • nicklouse
    nicklouse Posts: 50,675
    Matt21 wrote:
    Hi and thanks. It's a 105 5703 and is fitted correctly. Low limit stop is fully released and the bb has a spacer fitted to move it out from the shell.
    What cranks? Why are you running a BB spacer?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • matt21
    matt21 Posts: 71
    They're sram truvativ elita with GXP BBs and the shell is 68mm so no spacer should be needed. Originally I thought a spacer would make the chain drop onto the inner ring - that was before I realised that the chain isn't engaging with the outer plate of the mech as it should.
  • matt21
    matt21 Posts: 71
    Anyone any ideas?
  • nicklouse
    nicklouse Posts: 50,675
    Matt21 wrote:
    They're sram truvativ elita with GXP BBs and the shell is 68mm so no spacer should be needed. Originally I thought a spacer would make the chain drop onto the inner ring - that was before I realised that the chain isn't engaging with the outer plate of the mech as it should.
    remove the spacer before you il the bearings. they are not designed to be preloaded.

    so get it set up correctly and make sure you do the bolt up tight enough. and greased where it should be.

    http://cdn.sram.com/cdn/farfuture/KjsIO ... 03-000.pdf
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown

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