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Weird shifting problem with RD 105 ?!?

drPDdrPD Posts: 6
edited October 2008 in Workshop
My bike is new (~300 Km) full Shimano 105 9 speed front 53-39 and back 12-25.

I am having a problem shifting at the end of cassette (smallest cog) while I am on the big ring. When I'm on the road, shifting is sloppy and won't shift at all from 13 to 12 cogs. Sometimes I have the same problem in shifting from 15-13 cog. When it's in the stand or when I am on road very ease on pedal, shifting is perfect, works how it's supposed to, and I can't detect any problems. When I'm in the small ring, shifting is just fine. It's only the big ring where I am having trouble.

I have taken the bike to LBS to fix it after reading many posts here where I found to check the hanger alignment and I have insisted they check the hanger alignment. They correct the hanger aliment (and check other things) but the problem exists.

I visited techdocs.shimano.com before and download FD and RD docs. I tune FD and RD without problem (I have two another bikes and there is no problem in tuning FD and RD).

The problem is weird because is appear only under load on road but no in the stand or when I am on road very ease on pedal. I can shift from 13 to 12 cog but I need to tap two time shifter to make click and drop from 13 to 12 cog.

Any ideas where to look next?
:?

Posts

  • andrewjosephandrewjoseph Posts: 2,165
    check the limiter screws on the RD, it may need to be loosened a little.

    Check for chain alignment, maybe the chainrings are too far outboard.
    --
    Burls Ti Tourer for Tarmac, Saracen aluminium full suss for trails
  • drPDdrPD Posts: 6
    Thank you for answer.

    I will check this in the afternoon.
    8)
  • Monty DogMonty Dog Posts: 20,614
    Re previous post - assuming you've got a Shimano chainset then chainline problem could be dismissed. www.parktool.com has plenty of online info on bike mechanics. You may have some dirt in the shifter which is preventing the ratchet from dropping fully home - check that the there isn't any handlebar tape under the hoods fouling the internals or that the hood is correctly fitted. Also check the cable run under the BB and that the inner cable isn't frayed at any point - if you release the gear cable does the mech stop further out - in which case, it's a cable/indexing problem.
    Make mine an Italian, with Campagnolo on the side..
  • drPDdrPD Posts: 6
    Monty Dog wrote:
    Re previous post - assuming you've got a Shimano chainset then chainline problem could be dismissed. www.parktool.com has plenty of online info on bike mechanics. You may have some dirt in the shifter which is preventing the ratchet from dropping fully home - check that the there isn't any handlebar tape under the hoods fouling the internals or that the hood is correctly fitted. Also check the cable run under the BB and that the inner cable isn't frayed at any point - if you release the gear cable does the mech stop further out - in which case, it's a cable/indexing problem.


    How can I remove dirt (or clean) shifter?
    My bike has been 3 years in the LBS and I suspect the grease in shifter become sticky or dirty.
  • alfabluealfablue Posts: 8,497
    drPD wrote:
    Monty Dog wrote:
    Re previous post - assuming you've got a Shimano chainset then chainline problem could be dismissed. www.parktool.com has plenty of online info on bike mechanics. You may have some dirt in the shifter which is preventing the ratchet from dropping fully home - check that the there isn't any handlebar tape under the hoods fouling the internals or that the hood is correctly fitted. Also check the cable run under the BB and that the inner cable isn't frayed at any point - if you release the gear cable does the mech stop further out - in which case, it's a cable/indexing problem.


    How can I remove dirt (or clean) shifter?
    My bike has been 3 years in the LBS and I suspect the grease in shifter become sticky or dirty.
    I think it is more likely the cable / cable outer - they fill with gunk and get very sticky, this effects shifting to the smaller sprockets because it is purely the mech spring doing the work, rather than your hand's efforts in shifting to higher sprockets. I use fully sealed "Mudlovers" cable sets and they run smooth for years (fixed a similar problem that kept recurring despite frequent cleaning and lubing the cables). If you undo the cable from the mech end you should be able to feel any excess friction as you pull the cable through the outer.
  • peanutpeanut Posts: 1,373
    turn the bike upside down and check that there is not a lot of crud in the cable guides. Give them a good clean and apply a little grease.
    Your rear mech may have a weak return spring. You could try fitting another rear mech .I know it will take some time but it may eliminate the problem.
    Also check that you have some nice big gentle curves on your gear cables. You could try replacing your inner gear cables or greasing your existing.
  • drPDdrPD Posts: 6
    I suspect that my rear mech may have a weak return spring. How can I check it and how to replace?

    :idea:
  • peanutpeanut Posts: 1,373
    peanut wrote:
    Your rear mech may have a weak return spring. You could try fitting another rear mech .

    :wink:

    its very easy. Don't even need to remove the chain. Just remove the lower half of the rear mech cage
  • atticaattica Posts: 2,362
    Check that the gear cable entering the shifter (on the side of your hoods) isn't frayed - the cable can enter the shifting mechanism and will eventually stop the whole thing upshifting.
    "Impressive break"

    "Thanks...

    ...I can taste blood"
  • nicklousenicklouse Posts: 81,520 Lives Here
    if the bike has been sat in a shop for 3 years I would sugest a replacement of the cable as the first thing to do. As the symptoms sound just like sticky cables.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • drPDdrPD Posts: 6
    I have solved the problem and thank you all to participate in solving the problem. I hope this could help you if you face the similar problem. :D

    The housing near RD was bended immediately upon leaving the barrel adjuster. This was actually bending the housing end cap.
    When I put the housing below quick release axle the housing near RD is not bended immediately upon leaving the barrel adjuster.
    Yes this is temporary solution and I need a longer housing in this case allows the housing to enter straight.
    8)
  • peanutpeanut Posts: 1,373
    drPD wrote:
    I have solved the problem and thank you all to participate in solving the problem. I hope this could help you if you face the similar problem. :D

    The housing near RD was bended immediately upon leaving the barrel adjuster. This was actually bending the housing end cap.
    When I put the housing below quick release axle the housing near RD is not bended immediately upon leaving the barrel adjuster.
    Yes this is temporary solution and I need a longer housing in this case allows the housing to enter straight.
    8)

    :shock: :?: and again in English :wink:
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