Jumping Chain just on 11 tooth

DB2012
DB2012 Posts: 30
edited November 2013 in Workshop
Hi All. Recently installed new chain rings, new chain and new cassette. Its all working fine except when on the big ring and in the 11 tooth and pushing hard the chain jumps. Thing is its not every revolution, just every 15 seconds or so when at a constant effort. Any ideas what it could be? Its difficult to reproduce as its such a hard gear so im struggling. Could it be chain length? Or maybe a few turns of the barrell adjuster? Any tips much appreciated. Cheers.

Comments

  • keef66
    keef66 Posts: 13,123
    If it's a Shimano cassette did you fit it using the 11t lockring supplied?

    If you inadvertently use a 12t lockring it will foul the chain when in the 11t sprocket, and this can make it skip under load.
  • Rightarmbad
    Rightarmbad Posts: 216
    Or it may simply be the joiner pin not fitted correctly and when you are in the 11 tooth the tighter radius shows up that the link is tight and doesn't wrap cleanly around the cog.
  • cycletech
    cycletech Posts: 44
    I would check;
    When you are in the highest gear "11t sprocket & big chainring"
    That the chain is running inline with the derailleur, the H screw may need adjusting
    The gear cable may be over adjusted and chain is catching the next sprocket. (Adjust H stop screw & re-Index gears)
    Gear hanger slightly bent
    Rear derailleur worn
    Jockey wheels worn or loose
    If mudguards fitted; could be catching stay bolt
    And like Rightarmbad said "could be a stiff link"!

    der_parts.gif
    Check/adjust chain alignment and adjust H screw so derailleur aligns chain with 11t sprocket

    der_hlimit.gif

    der300.jpg
    Check for wear

    Worn+jocky+wheels.JPG
    Check jockey wheels for wear
    Mobile Bicycle Mechanics Specialist http://www.cycletechuk.co.uk
  • smidsy
    smidsy Posts: 5,273
    Some possible causes
    The jockey wheel is not inline (which you would achieve as shown above) or
    The tension on the cable is not right (which just needs a few turns of the barrell adjuster) or
    The 11t is worn more than the rest (do you use it lots?).
    Yellow is the new Black.
  • cycletech
    cycletech Posts: 44
    smidsy wrote:
    Some possible causes
    The tension on the cable is not right (which just needs a few turns of the barrell adjuster) or
    The 11t is worn more than the rest (do you use it lots?).


    It's fitted with a new cassette!
    Mobile Bicycle Mechanics Specialist http://www.cycletechuk.co.uk
  • Nairnster
    Nairnster Posts: 602
    I Would say:

    Check the b angle screw (think it's called that) that tightens against the derailleur hanger. Screw it in to make sure the top jockey wheel is not fouling the smallest cog.
  • lackofgrip
    lackofgrip Posts: 851
    I'm having a similar problem, all new drivetrain SRAM Rival setup. It's just so annoying. let me know if you find a cure.
  • lackofgrip
    lackofgrip Posts: 851
    Nairnster wrote:
    I Would say:

    Check the b angle screw (think it's called that) that tightens against the derailleur hanger. Screw it in to make sure the top jockey wheel is not fouling the smallest cog.

    Can the 'B' screw be screwed in/out too far?
  • Nairnster
    Nairnster Posts: 602
    Too far in it would bottom out, but you only turn it as far as it needs to make sure the jockey wheel clears.

    Too far out and it would fall out.
  • lackofgrip
    lackofgrip Posts: 851
    Nairnster wrote:
    Too far in it would bottom out, but you only turn it as far as it needs to make sure the jockey wheel clears.

    Too far out and it would fall out.

    How close should it be? Or does it just not need to foul the cassette?
  • Nairnster
    Nairnster Posts: 602
    I screw mine in until the jockey wheel is as close as I can get it without it fouling the smallest cog. Before you touch it though, is it actually fouling?

    Its explained quite well here, the section B screw adjustment

    http://www.parktool.com/blog/repair-hel ... derailleur
  • dodgy
    dodgy Posts: 2,890
    DB2012 wrote:
    Hi All. Recently installed new chain rings, new chain and new cassette. Its all working fine except when on the big ring and in the 11 tooth and pushing hard the chain jumps. Thing is its not every revolution, just every 15 seconds or so when at a constant effort. Any ideas what it could be? Its difficult to reproduce as its such a hard gear so im struggling. Could it be chain length? Or maybe a few turns of the barrell adjuster? Any tips much appreciated. Cheers.

    Seen this before. It happened to me when I was using a KMC Missing Link on a Mavic 10v chain. The 'Missing Links' are directional, and if you put them on the wrong way, they catch on the cassette body when negotiating the tight radius of 11t sprocket.

    The problem went away when I installed a Shimano Ultegra chain and took more care fitting the Missing Link.
  • lackofgrip
    lackofgrip Posts: 851
    Park Tools recommends 6mm between top jockey wheel biggest rear ring when fitting SRAM. Planet X had set it at 22mm impressive. NOT. :mrgreen:

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