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Rear Derailer - Is Always One Gear Too High

Discussion in 'Bicycle Mechanics and Repairs' started by pbar, 30 Mar 2008.

  1. pbar

    pbar New Member

    I have an issue with my rear derailer on my MTB, it's a Shimano 6 speed, and it's always a gear in front. i.e. when I shift to 3rd gear, it jumps to the 4th sprocket, etc. When in 1st gear, it's on the 2nd sprocket, so if I adjust the chain and manually place it on the 1st large sprocket (i.e. 1st gear), and set off, it immediately jumps to the 2nd sprocket, giving me 2nd gear, then I'm back to being a gear in front. So, I'm missing a gear, as I have no 1st, and I'm always a gear too high. I haven't 'messed' with it much yet, thought I'd ask first, as it may be a simple adjustment which I can hopefully do perhaps. Thanks!
     
  2. betty swollocks

    betty swollocks large member

    This sounds like a simple question of cable tension.
    Manually place your chain on the second smallest sprocket (2nd one in) and select the matching gear on the shifter. Now cycle the bike (or put it in a stand and rotate the cranks) and see what he chain is trying to do. If the chain tries to skip onto a bigger sprocket or actually skips up, the cable is too tight and needs to be loosened. To do this wind the barrel adjuster in (clockwise). Do this a quarter of a turn at a time until the chain stays on the appropriate sprocket.
    Next, click the shifter up one gear and see if the chain moves up accordingly. If it does, click up once more and observe whether he chain moves up accordingly again. Keep on repeating this until all clicks on the shifter match all the sprockets on the cassette.
    Remember, if the chain shifts up too much, it's too tight and if the chain is too sluggish coming down, the cable is not tight enough and needs tightening by winding the barrel out - anticlockwise.
    This process may involve a bit of trial and error before all gears change sweetly up and down.
    The gears may behave slightly differently actually riding than on a workstand.
    Good luck and hope this helps.
    Helpful youtube video
     
  3. pbar

    pbar New Member

    Thanks for your reply. I have done as you mentioned and it's been much better. I can now run through all the gears, one by one, it's the best it's been for ages. I had to turn the adjuster anti-clockwise, quite a way in fact, must have been 3 full turns or so before the gears started to change up/down properly. I only had a little run out tonight as a test, but very pleased. It took me about twenty thousand hours though, another turn, another turn, etc. I also cleaned some crud and dog hair (don't ask) out of there and I think I'll have partially black finger skin for several years. Oh, and the added bonus of a super strength left bicep, with holding the rear end of the bike up by the saddle for what seemed like hours on end whilst I changed gears and spun the pedals with my other hand to check the adjustments. I'm lovin it! Thanks again.
     
  4. John Ponting

    John Ponting Über Member

    Location:
    Herts
    Reaqdy for next time - have you got a shed with a wooden beam or plank in the roof? Screw a hook or eye in to the beam, hook in a lop of washing line and hang the bike from the saddle. If you have enough space, use 2 screw in hooks and hang the bike from the handlebars as well as the saddle.
     
  5. betty swollocks

    betty swollocks large member

    You're very welcome: glad you got it sorted.

    Before I got a workstand, I used to hook the saddle over a broom handle resting across the backs of two chairs!
     
  6. pbar

    pbar New Member

    Hey, you know, my garage has a small pulley wheel fixed into the concrete ceiling. I always wondered what it was for, too small/weak to be of any use car-mechanics wise, so now I wonder if it was for bikes?!
     
  7. pbar

    pbar New Member

    That's another great idea. I was also thinking how I could build something from some timber I have...
     
  8. Tynan

    Tynan Veteran

    Location:
    e4
    I bought a track stand for £29, only had the bike on it once but it looked really good after twenty years of upside down

    and latex gloves
     
  9. pbar

    pbar New Member

    Errr.....are we still talking about bike stuff here.....:biggrin:
     
  10. summerdays

    summerdays Cycling in the sun Staff Member

    Location:
    Bristol
    Mechanic's wipes are good too:biggrin: