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Overshifted on front and now rear shifting is stuffed

Swansea_DaveSwansea_Dave Posts: 73
edited December 2014 in Workshop
I have a Shimano 105 10 speed set-up, compact chainrings. My front derailleur overshifted and threw the chain over the large chainring, wrapping the chain around the pedal arm. Ouch. It was a real mess. (This was entirely my fault as the derailleur limit screw wasn't properly adjusted - lesson learned!)

Anyway, I replaced the chain - which had some bent links - but I just can't get the shifting sorted on the rear cassette. The chain keeps slipping / jumping between cogs when under pressure.

i) I have adjusted the indexing several times.
ii) I have lubricated the shifter cables, and lubricated the STI units.
iii) The new chain is the same length as the old one.
iv) I have tried swapping the rear cassette, no difference.

The rear shifting was 100% before the 'chainring incident'.

The rear derailleur looks straight to the eye, but I haven't e.g. checked the hanger for alignment.

All advice much appreciated. This is driving me nuts.

Cheers, Dave

Posts

  • JackPozziJackPozzi Posts: 1,191
    First thought is how many miles did you have on the setup before? You said you tried a different cassette, was it a brand new one? Could just be both cassettes have been worn and don't work well with a new chain?
  • Probably 1,000 miles or so on the original cassette. The other one I tried was almost new (less than 200 miles) so it should have been fine.

    Thanks for your reply.
  • JackPozziJackPozzi Posts: 1,191
    Hanger would be the next guess then, was it a bit of a crunchy mess?
  • Yes, it was carnage. I had to take off the chainset and polish out the scratches (gouges) on the crank arm and the spider.
  • pinnopinno Posts: 42,774
    Silly question time:
    Did the chain twist the rear mech body?
    Have you taken the jockey wheel cage off to see is it is bent in any way?
    Bit twiddly, but have you got another rear mech to put on just to see if the gears work properly?
    Is the rear mech twisted in the hanger aperture? - check the thread.
    Have you checked the jockey wheels themselves?
    Did you bend the chainrings by any chance?
    seanoconn - gruagach craic!
  • Silly question time:
    Did the chain twist the rear mech body?
    Have you taken the jockey wheel cage off to see is it is bent in any way?
    Bit twiddly, but have you got another rear mech to put on just to see if the gears work properly?
    Is the rear mech twisted in the hanger aperture? - check the thread.
    Have you checked the jockey wheels themselves?
    Did you bend the chainrings by any chance?

    Not sure about silly, they are all very useful suggestions. Thanks.

    I have a working set-up (ceiling hooks) which places my bikes at a convenient height so I can get 'up close and personal' with the drive train. It all look fine when I'm turning the pedals without load, nothing looks obviously out of alignment - although there is the odd skip and it just doesn't change sweetly.

    I do have another rear mech that I can try, but first I'm going to check the hanger alignment as it should be less hassle. I've just ordered the tool so I'll get on to it one evening this week.
  • pinnopinno Posts: 42,774
    Silly...chance?

    Not sure about silly, they are all very useful suggestions. Thanks.

    I have a working set-up (ceiling hooks) which places my bikes at a convenient height so I can get 'up close and personal' with the drive train. It all look fine when I'm turning the pedals without load, nothing looks obviously out of alignment - although there is the odd skip and it just doesn't change sweetly.

    I do have another rear mech that I can try, but first I'm going to check the hanger alignment as it should be less hassle. I've just ordered the tool so I'll get on to it one evening this week.

    Post an update is you get it sorted.
    seanoconn - gruagach craic!
  • I picked up a Cyclus gear hanger adjuster at a princely £24 odd, http://www.wiggle.co.uk/cyclus-gear-han ... ment-tool/

    Its a little agricultural but works well. When I checked the hanger alignment it was about 12-15mm out at the top of the arc (12 o'clock) - and the same at the bottom (6 o'clock), obviously. The angle was such that the bottom of the derailleur cage would have been pointing in towards the spokes by say 4-5mm or so - that seems like a pretty major misalignment. :shock:

    Having adjusted the hanger using the tool and then rechecked and adjusted the derailleur cable & indexing, it all seems OK. The shifting on the bike stand seems good, so I'll go for a spin tomorrow and report back. Fingers crossed.
  • jgsijgsi Posts: 5,029
    A new hanger even for a pricey Caad10 is only a tenner... if a hanger takes a bang then I'd rather replace it as just.
    I have enough ugly pieces of metal cluttering up my toolkit as it is.
  • Thats probably very good advice. The bike is an aluminium Specialized Allez and has done thousands of miles - training, sportives, triathlons, commuting, all sorts really. It hasn't been crashed and I don't remember it being dropped but there may have been a few minor topples over the years. I guess it all adds to fatigue of a part that is, after all, designed to fail before the derailleur or the frame does.
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