Drivetrain Clunk?

laurentian
laurentian Posts: 2,471
edited April 2013 in Workshop
I have an intermittent problem with my 9 sp Sora.

When out riding, every so often I feel a soft clunk, every second revolution of the pedals, through the drive side pedal.

Out yesterday and by looking down to the cassette, I noticed that, coinciding with the clunk, the chain took a slight jump to the right and then back into position. It does not slip onto another cog.

I should declare at this point that this has only happened since I changed my chain and cassette a couple of weeks ago.

As ever, any help is greatly appreciated.
Wilier Izoard XP

Comments

  • gaddster
    gaddster Posts: 401
    Perhaps you need to try and re-index the gears, new cassette and chain will likely throw that off slightly. Use the barrel adjuster on rear mech to do this, not the high/low limit screws.

    Good guide here how to do it..

    http://www.youtube.com/watch?v=SkzvfCaIbyQ
    ARTHUR
    "Hello oh great one"
    LARRY
    "Are you talking to me or my ass?"
  • keef66
    keef66 Posts: 13,123
    You should check very carefully the point at which you joined the chain.

    Good chance it's either a stiff link, or a link that's in the process of coming apart.
  • laurentian
    laurentian Posts: 2,471
    keef66 wrote:
    You should check very carefully the point at which you joined the chain.

    Good chance it's either a stiff link, or a link that's in the process of coming apart.

    This makes a lot of sense. Indexing is something that scares me but I will have a look at it if needs be!

    I had a really good look at the chain last night and couldn't seem to see anything wrong. That's not to say there is nothing wrong with it and I will be looking again tonight.

    Is there an easy way or a knack to find the point at which I joined the chain? Sounds like a bit of a daft question but I stared at the thing for ages last night and I can't seem to replicate the problem when spinning the pedals on the stand.

    Is there any danger or downside to removing the chain for a real good look at it and then re-joining again?

    Really appreciate your help.
    Wilier Izoard XP
  • keef66
    keef66 Posts: 13,123
    How did you join the chain? Quick link? Shimano snap-off pin? If you used one of the Shimano snap-off joining pins and you want to break the chain again you should push out one of the normal pins.

    http://techdocs.shimano.com/media/techd ... 686193.pdf

    If you used a quick link (KMC, Wipperman, SRAM etc) then it's a bit simpler
  • laurentian
    laurentian Posts: 2,471
    keef

    This is all a bit new to me so excuse my ignorance. I used a pin that came with the chain. I didn't snap anything off . . . it looked to be the same length as the others.

    It simply pushed through using the same tool I used to "break" my old chain. The frustrating thing is that I remember, when I finished doing it, wondering whether I'd pushed it in far enough. Obviously the ends of the other pins stand a little proud of the plates but it did cross my mind - this is why your suggestion seems to make sense to me. My thought was to get another "pin" from LBS, "break" my chain and then lay it out so that I can see if there are any obvious problems with it, particularly with my original join . . . if I can find it!

    Thanks for your continued help.
    Wilier Izoard XP
  • keef66
    keef66 Posts: 13,123
    Another thought occurs to me; did you shorten the new chain to the correct length before fitting it?

    I'd strongly recommend joining the chain with a KMC missing link or the SRAM or Wippermann equivalent. Just make sure you get the 9 speed Shimano version. Or if you prefer to use a Shimano joining pin, again make sure you buy the 9 speed version and follow the instructions I linked to.

    Find the pin you joined it with and remove that link. (The holes in the outer plates that the pin went through will have been enlarged and cannot be used). You should leave an inner half link at each end of the chain, which you can then join with your chosen joining link.
  • laurentian
    laurentian Posts: 2,471
    Yes, I'm pretty sure I got the chain length right (I used a formula that someone else linked me to on this site - to the park tools website I think) - it looks OK with the jockey wheels being in vertical alignment when "Big front, small rear" cogs engaged.

    Finding the pin I joined it with is a problem!!

    However, as I type, the Mrs is in town and I have diverted her to LBS for KMC/Wipperman chain link.

    Really appreciate your help. I'm trying my best to learn this maintenance thing as I go along and, although LBS are brilliant, putting a new chain on should be well within my ability (despite current problems).
    Wilier Izoard XP
  • laurentian
    laurentian Posts: 2,471
    Well, I've found the offending link!

    It looks like, rather than clicking into the hole on the "inside" outie chain plate, the pin has not gone into the hole and pushed the plate proud of the rest of the chain - I'm guessing this was the pin that I put in when changing the chain.

    Going to have a wrestle with it tonight to see if i can get it to engage properly, otherwise will be replacing with a "missing link" as advised.

    Keef, your help has been invaluable - thanks again.
    Wilier Izoard XP
  • keef66
    keef66 Posts: 13,123
    Best you found it when you were looking for it, rather than 25 miles from home as darkness is falling and the rain's beginning :D
  • laurentian
    laurentian Posts: 2,471
    keef66 wrote:
    Best you found it when you were looking for it, rather than 25 miles from home as darkness is falling and the rain's beginning :D

    Absolutely! Anyway, link replaced last night and a quick spin around the block shows that all is now well again!

    Thanks again . . . dare say I'll be back following my next maintenance attempt!
    Wilier Izoard XP
  • keef66
    keef66 Posts: 13,123
    Marvellous!