front derailleur adjustment problem

jainsy
jainsy Posts: 37
edited May 2011 in Workshop
I've been attempting to follow an online youtube video to adjust my derailleur. It seems pretty simple, and i'm sure I've done everything correct.

However, I can only shift from the small front cog to the large cog and not back. It shifts smoothly but this is all.

I've been over it loads and don't know what im doing wrong. Can anyone help?

Comments

  • sungod
    sungod Posts: 16,878
    small to large is done by the cable pulling

    large to small, the cable is de-tensioned and it relies on a spring to shift back

    so if the cable/outer is sticky or worn/damaged, it can cause the effect you are seeing

    a broken spring, or gundged up pivots in the front mech can also do it, but cable troubles are more likely
    my bike - faster than god's and twice as shiny
  • Liam Whyte
    Liam Whyte Posts: 17
    +1 for cable problems. If it isn't damaged then take it out of the outer sleeve and give a good wack of grease and reinsert it. Also clean and de-grease your front mech if it needs it.
  • jainsy
    jainsy Posts: 37
    Thanks guys. I think it must be cable problems as its just not coming back and the shifter seems to get stuck.

    This may be silly but what is the outer sleeve?
  • sungod
    sungod Posts: 16,878
    the inner is the cable itself, the outer is the that the cable runs through

    there are two kinds of cable, one for brakes, one for gears, brake is thicker

    there are two kinds of outer, one for brakes, one for gears, they are constructed differently

    *never* use gear cable/outer for brakes

    you can try flushing the outer clean with solvent etc, but it's not a bad idea to simply change cables/outer every few years, as they get worn/stretched/sticky

    you can buy kits of cable, outer and ferrules...

    http://www.wiggle.co.uk/transfil-kble-s ... cable-set/

    http://www.wiggle.co.uk/transfil-shiman ... cable-set/

    for the outer you need some decent cutters so that the ends are round and don't snag the cables

    read about how to do it first, then take it slow, it is not complex but there are several steps to go through

    best to do one side first, say left, then if things are slow you can finish and do the right another time

    unwrap bar tape far enough

    undo old cables, pull through

    take off old outers

    cut new outer to same lengths (to avoid mix ups, do the brake first, then the gear)

    thread new cables and outers, tape outer to bars at 2-3 places

    re-wrap bar tape

    clamp cable to deraiileur and brake, adjust to correct length, cut surplus

    repeat for other side

    the park tools website is a good source of pictures/instructions...

    http://www.parktool.com/blog/repair-help
    my bike - faster than god's and twice as shiny
  • bruce225
    bruce225 Posts: 129
    Hi are your HI-LOW screws set correctly,just that I've done it before were the screw were set what i thought was right but wouldn't allow for full movement of front mech...

    My advise would be to put both screws just in a neutral position and check if you can get the mech to move freely again just using cable adjustment..

    I know everyone will say you need to do the screws first but at least you'll take that out of the equation...
  • Twostage
    Twostage Posts: 987
    Could be cable tension too tight. Not sure which video are watching. Might be worth undoing the cable from the mech and making sure the derailleur moves in and out as far as you think they would need to go adjusting the limit screws and lubricating as needed. Then make sure the shifter has selected the smallest ring so the cable is at its slackest and re-attach the cable so there is only a small amount of tension. Should be near enough at this point.