Problem shifting gears

dUNC
dUNC Posts: 73
edited November 2007 in Workshop
Hi all.

I'm having a problem shifting gears. I'm no techie, so bear with me (or advise me to go to the LBS if I sound lost!)...

When trying to change up a gear (on the back, and seems to be worse when I'm in the big ring) it either takes a couple of seconds to change - I flick the switch, hear it ping at the back, but teh gear doesn't change, then suddenly it will change (normally when I've started going up a hill and want to change back down :)).

I've worked out I can get round this by shifting up two gears, and then dropping down one - the second shift seems to move it into the gear I want, then I drop it down before the second gear change happens. This seems to be worse in the bigger cogs at the back (higher/lower gear?), once I get into the smaller cogs it seems to shift pretty quickly.

I don't seem to have much of a problem dropping down the gears, although sometimes it sticks going from 3rd down to 2nd (biggest), which a gentle nudge of the switch fixes.

Annoyingly this has happened suddenly, I've not noticed a degradation in switches so that I could sort something out sooner (I would've thought that it would be something that would have got worse over time, but it's like something's been knocked out of line, but it's just been locked up at the house!).

Does anyone know what I should do? Thanks in advance!

Comments

  • Bronzie
    Bronzie Posts: 4,927
    Probably just caused by cable stretch to the rear mech - have you tried altering the adjuster on the rear mech?

    If not, it's the black or grey knurled plastic collar that the outer cable passes into where it goes into the rear mech - turn it anti-clockwise by 1/2 a turn at a time to make the cable slightly tighter and see if this solves it.

    Have a look at "Checking the Rear Indexing Adjustment" here http://www.parktool.com/repair/readhowto.asp?id=64
    It's a Lifestyle! -+-+- Coggan Training Levels
  • pw1brown
    pw1brown Posts: 243
    If the above doesn't fix the problem, check for dirt inside the outer plastic sleeve near the bottom end of your gear cable too. If there is, wash the casing out thoroughly with oil (or soapy water for that matter). You'll near to detach the cable from the rear derailleur to clean it properly. Dry it before you reattach it all, and lubricate the cable with only a minimal amount of oil, so as not to attract more gunge.
    My bikes
  • onbike 1939
    onbike 1939 Posts: 708
    pw1brown wrote:
    If the above doesn't fix the problem, check for dirt inside the outer plastic sleeve near the bottom end of your gear cable too. If there is, wash the casing out thoroughly with oil (or soapy water for that matter). You'll near to detach the cable from the rear derailleur to clean it properly. Dry it before you reattach it all, and lubricate the cable with only a minimal amount of oil, so as not to attract more gunge.


    ^^^^ the most likely cause in that this happens when coming down the gears.
  • peanut
    peanut Posts: 1,373
    check the cable guide under the bottom bracket things can get very rusty this weather . Spray and brush with old tooth brush with WD40 then apply some light machine oil to the guide.
    Check the rear gear cable hasn't started to unravel inside the outer cable. You should disconnect the cable from the rear mech then try moving the rear mech with your fingers, it should move freely. Could be grit or stone trapped in the mech.
    Check the cable moves freely whilst its disconnected by operating your STi levers. If you mark the cable next to the mech with felt tip before removal it should be possible to put it back on the rear mech without needing to adjust anything.
    You've now checked the whole system so you should have found the problem

    You can test the whole system by turning the bike upside down and turning the crank whilst running the gears up and down.

    :wink:

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