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Front Mech

Discussion in 'Bicycle Mechanics and Repairs' started by HLaB, 12 Feb 2008.

  1. Its really hard, if not impossible to shift up to the large (52T) chainring on my bike of late. I thought this might be the cables, so I replaced these. The cables run freely but the gear change is just as bad. My next thought was the front mech its self. It appears to be in good condition however the recoil spring (or whatever its called) although clean may be a little taught.

    My next step is to soak the mech in degreaser and relube.

    Has anybody any more ideas? btw Its a Shimano road mech (Tripple) with rapid fire shifters.
     
  2. fossyant

    fossyant Ride It Like You Stole It!

    Location:
    South Manchester
    How freely does the shifter move ?

    Does it shift between middle and inner OK ?

    Is it 'physically ' hard to shift up, or will the chain not shift up - i.e. doesn't grab.... - could be dirt in the mech stop screws, stopping it shifting far enough, or as the cables have been changed, does the mech stop need adjusting ?
     
  3. Thanks Fossant,
    The shifters independant of the front mech shift quite freely.
    It takes a little bit of effort but not too excessive to shift between middle and inner.
    As you say it is 'physically' hard to shift up. My first thought was the limit screws too but these are clear and move well, no grinding.
     
  4. Putting it all back together tonight I think its my Shifter which is away. If I slacken the cable via the limit screws barrel adjuster I can change up from the middle ring to the outer (52t) ring. However shifting from the lower to middle ring is a little short unless I put the shifter quite a bit past no. 2.
     
  5. bonj2

    bonj2 Guest

    if it's too stiff - check the cable routing. i.e. how the cable loops round the bolt that attaches it to the front mech.

    I had this problem... make sure the cable is such that the position it pulls is as far away from the pivot as it can be, if you know what i mean. There's a little 'lug' on mine which i did have it inside of, but it was a bit stiff so i put it outside, and it shifts much better now.

    and you don't "slacken the cable via the limit screws". The limit screws control the range of motion of the mech, and should be adjusted first, before you start doing anything with cable tension. The limit screws don't have any effect on cable tension.

    first get the mech itself in the right position.
    get the limit screws in the right position, without doing anything with the cable tension or the shifter. Move the mech by hand or by pulling the cable with your hand.
    THEN get the cable tension set correctly.
     
  6. John the Monkey

    John the Monkey Frivolous Cyclist

    Location:
    Crewe
    HLab, might be worth running the derailleur model with some words describing the problem through Google...

    My Tiagra front mech has similar problems now and then (doesn't shift easily to the big ring, and then doesn't shift there at all), and apparently this is a fairly common thing, easily adjusted. (In my case it's cable stretch, and the barrel adjuster on the shifter sorts it out).
     
  7. Sorry Bonj I meant to say barrel adjuster:blush:

    I gave up playing about with it when I got it shifting fairly well from the middle ring to the outer (52t) ring. OK the shifting from the Granny to middle seems to be a little short but tightening the cable makes the shift from middle to upper to awkward and I use these rings the most.
     
  8. bonj2

    bonj2 Guest

    don't know about you but mine shifts from granny to middle better when the rear is not on the biggest sprocket, i.e. when you're in the lowest gear and you get to the top of the hill change up on the rear mech first, then the front - rather than front first then rear.