Clunking in lower gears

spinndrift
spinndrift Posts: 185
edited May 2011 in Workshop
I've got a clunk when my right crank passes 12 o'clock position but it's only really noticeable in the bottom few gears.

I'm running SRAM apex and have done about 600 miles on the bike - the BB isn't loose, the cranks aren't loose, no dodgy teeth on the small ring and the the rear hanger is tight.

Any one got any ideas?
Cheers

Andy
Cyclist, Massage Therapist & Ice Cream Genius
Andrew Creer Massage

Comments

  • Valy
    Valy Posts: 1,321
    Have a look at the cahin at the back - see if it is not set up dead on the gog's teeth.
  • buder
    buder Posts: 154
    I have a similar issue going on although I would describe mine as a loud scrapping noise in exactly the same circumstances as yours.

    I am thinking chain line issues in my case and perhaps a case of fd flex in which the inner chain cage is hitting the chain. If this is the case its concerning as it seems to be doing it in
    25, 23, 21 and 19 if I really try and torque it out the saddle.

    Cranks seem tight, I thought I could feel a very slight movement in the bb but am not 100% certain of this. Cassette is tight, rear mech is indexed properly just when out the saddle spinning in those gears !?.
  • spinndrift wrote:
    I've got a clunk when my right crank passes 12 o'clock position but it's only really noticeable in the bottom few gears.

    I'm running SRAM apex and have done about 600 miles on the bike - the BB isn't loose, the cranks aren't loose, no dodgy teeth on the small ring and the the rear hanger is tight.

    Any one got any ideas?

    Your crank arm could be clipping the front mech, slght adjustment of one of the screws should allow enough clearence.
    buder wrote:
    I have a similar issue going on although I would describe mine as a loud scrapping noise in exactly the same circumstances as yours.

    I am thinking chain line issues in my case and perhaps a case of fd flex in which the inner chain cage is hitting the chain. If this is the case its concerning as it seems to be doing it in
    25, 23, 21 and 19 if I really try and torque it out the saddle.

    Cranks seem tight, I thought I could feel a very slight movement in the bb but am not 100% certain of this. Cassette is tight, rear mech is indexed properly just when out the saddle spinning in those gears !?.

    The front shifters should have a stop between each gear stop (trim) this should give a little extra chain clearence while moving between the rear cogs
  • spinndrift
    spinndrift Posts: 185
    Indexing and high and low are fine but I think I may have found the issue.

    It doesn't clunk all the time but becomes noticeable on the long climbs and I have some play in the right pedal so I think it may be that when I am tired I start pedalling in squares and the carbon tubes make it resonate more.

    Typically I've been out tonight and it isn't bloody clunking but if it starts again going to fit some flat pedals.
    Cheers

    Andy
    Cyclist, Massage Therapist & Ice Cream Genius
    Andrew Creer Massage