Front mech not changing down

Discussion in 'Bicycle Mechanics and Repairs' started by banjoblues, 13 Aug 2007.

  1. banjoblues

    banjoblues New Member

    Hi folks. I've got a Shimano Sora triple front mech which is very reluctant to drop down on to the smallest ring. It just sits there and grates, even when the chain is on the largest cog in the rear cassette. Sorry if I'm teaching grannnies to suck eggs but on this mech, Low is "home" and you pull the cable tighter to change up a ring. Releasing the tension on the cable and a spring pulls the shifter across to a lower ring. Changing gear with the bike on a stand seems ok and, once it has changed, there is no problem. I've checked the cable isn't too tight and the "end stop" of the shifter isn't preventing it moving far enough across. The only other thing I can think of is that there is some friction either in the cable or in the mech that stops it moving across freely. The bike is virtually new and the lbs I bought it from will sort it if I take it back but I like to sort these things out myself if I can. Anybody got any thoughts?
  2. Smokin Joe

    Smokin Joe Legendary Member

    My first suggestion would be a sticking cable, but on a nearly new bike that should not be the case unless substandard inner or outer are frayed or breaking up.

    Try giving the mech a good clean and a squirt of WD40, you may have some grit in there jamming it. If it is not something that is easy to spot I would definately take the bike back and let the shop sort it.
  3. starseven

    starseven Guest

    Doesn't the endstop set the inner position of the front mech. Disconnect the cable set the endstop so the mech just pushes the chain onto the inner ring then try shifting up, one or two clicks should get the chain on the top but set the upper endstop so you dont loose the chain over the big ring.

    thats how I do it anyway, it should get the chain on and off the rings.

    If you want to fine tune a hammer of prybar may be needed.;):biggrin::biggrin:
  4. Mr Phoebus

    Mr Phoebus New Member

    Check this out on the Park Tool website.

    Like above, I'd guess on a less than smooth cable causing problems.
  5. bonj2

    bonj2 Guest

    remove the cable completely, or disconnect it so that it's completely slack at the mech end. What position is the mech in then?
    This test should at least enable you to tell whether it's the mech itself or the cable that's the problem.
  6. Keith Oates

    Keith Oates Janner

    Penarth, Wales
    Everytime I've had a problem like this it's been the cable'. Now if all cables were totally enclosed most of these problems would disappear!!!!!!!!!!!!!!!!!!!
  7. alfablue

    alfablue New Member

    Probably not relevant, but I had this a while back and eventually sussed out that they mudguard had moved slightly and was interfering with the mech.
  8. gbb

    gbb Legendary Member

    This happens every year on my Sora double.
    Corrosion or grime in the pivot does it every time, exactly as you describe.

    Theres a large dome headed allen bolt facing the back wheel. (IIRC)
    This is the main pivot point. Undo it a little, spray some WD over the area, manipulate the pivot some, tighten the dome bolt back up.

    The glory is you dont have to disconnect the cables etc.

    Its not something that happened to me in the summer mind, usually salt and crud related in the winter....but no harm trying and very quick to do.
  9. bonj2

    bonj2 Guest

    I'm an advocate of fully enclosed cabling...
    <smug>as they are on my mtb ;)</smug>
  10. Smokin Joe

    Smokin Joe Legendary Member

    Fully enclosed cables will corrode just as quickly as external ones. Water ingress is where the inner cable enters the outer, and that will be outside the frame. You will also have a few other points where water will get inside the frametubes.
  11. alfablue

    alfablue New Member

    My Mudlovers cables have a sleeve that runs right from where the nipple fits inside the shifter to 1mm from the nut on the mech. In a years use there has been no water ingress. Maybe this is different from "fully enclosed cables" some of which merely seal where the outer stops.
  12. gbb

    gbb Legendary Member

    I must be the luckiest guy in here :sad:
    5 or 6 year old Raleigh, shod with Sora thats done maybe 4000 miles, winter and summer.
    Original cables, sleeves, derailleurs, levers, brakes, even the pads ;)
    I dont think i've ever had the cables off..maybe put some WD down them once or twice.....

    I'll get my coat....
  13. OP

    banjoblues New Member

    Thanks guys

    It looks like an adjustment problem after all. I think the end stop was stopping the mech moving sufficiently.
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