New mech hanger, or new mech?

disgruntledgoat
disgruntledgoat Posts: 8,957
edited March 2009 in Workshop
My rear mech took a knock racing on Sunday (pulled right to move up, team-mate not paying attention, front wheel into rear mech) and I noticed afterwards it was rubbing the spokes when at the top of the cassette. It's a campagnolo chorus 10spd.

I've managed to bend it back to a position where it works however at all stages of this botch job I was "missing" a shift. For example, if I started clicking down the block, at one point the chain would move 2 sprockets rather than 1 and when I got to the bottom i had a spare click... As I say it works now, but my first shift (from the 11 to the 12) needs to be very soft in order to prevent a reoccurance of the problem.

I'm assuming if the mech is still making ten indexed shifts it's ok, I can't see any signs of damage other than a little chip in the laquer on the carbon plate where the limiter screws are. Likewise, theres nowt happened to the ergolever. Any suggestions?
"In many ways, my story was that of a raging, Christ-like figure who hauled himself off the cross, looked up at the Romans with blood in his eyes and said 'My turn, sock cookers'"

@gietvangent

Comments

  • onbike 1939
    onbike 1939 Posts: 708
    It could be that the hanger is bent even though the mech is ok. Better to take it to the bike shop and have it checked with the alignment tool. This shouldn't take too long as only the rear mech needs unscrewed without the chain needing to be broken.
  • Monty Dog
    Monty Dog Posts: 20,614
    Check the alignment of the jockey wheel cage on the mech, but in my experience it's usually the frame hanger that bends first. It depends on the construction/material of your frame and whether you can simply bend the hanger (steel/ti - OK) replace/bend a removeable hanger, or the frame needs to go back for a factory repair (e.g. bonded carbon drop-outs). You LBS will have an alignment / manipulation tool and will be able to confirm your options.
    Make mine an Italian, with Campagnolo on the side..
  • disgruntledgoat
    disgruntledgoat Posts: 8,957
    Monty Dog wrote:
    Check the alignment of the jockey wheel cage on the mech

    Dunderhead's question: How do I do that? Epic have a new mech hanger winging it's way to me... even if it's not that it's useful to have a spare.
    "In many ways, my story was that of a raging, Christ-like figure who hauled himself off the cross, looked up at the Romans with blood in his eyes and said 'My turn, sock cookers'"

    @gietvangent
  • Monty Dog
    Monty Dog Posts: 20,614
    The cage should be vertical and parallel to the centreline of the frame - look at it in a workstand from behind - a crash usually bends the mech inwards and make sure the pulley cage is clear of the spokes in the biggest sprocket.
    Make mine an Italian, with Campagnolo on the side..
  • John.T
    John.T Posts: 3,698
    The indexing is controled by the shifter so will not be affected by a bent hanger or mech. These will however affect where the indexing lines up with the cassette.
    My Fleet.
  • Mister W
    Mister W Posts: 791
    A bent mech or hanger will affect the indexing because the geometry of the mech (how it moves) will be affected. Difficult to explain but easy to see.
  • John.T
    John.T Posts: 3,698
    I'm assuming if the mech is still making ten indexed shifts it's ok,
    From the OP. It gives the impresion that indexing is at the mech not at the shifter. A bent mech or hanger will still allow the mech to move the correct distance, but maybe not in the right direction.
    My Fleet.

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