What's up with my rear derailleur?

seanoconn
seanoconn Posts: 11,673
edited February 2015 in Workshop
The arm is too high

6312E0D3-C4D2-4CBF-A45A-A90FC35DFF01_zpssuadb6bw.jpg

Shouldn't it be down here somewhere
F66416DE-CA1A-4F70-831D-9599BC2EC2B1_zpssammsbdv.jpg

I had a crash and the wheel has been off since I rode last.
Pinno, מלך אידיוט וחרא מכונאי

Comments

  • keezx
    keezx Posts: 1,322
    Chain is too long in the fist place and the spring of the top pivot seems broken.
  • keef66
    keef66 Posts: 13,123
    +1 - your chain looks miles too long (unless it's not sitting on a chainring in that first photo)

    Was it running with that length chain before your crash?
  • seanoconn
    seanoconn Posts: 11,673
    No, the chain just distorts when I push the arm down.
    Pinno, מלך אידיוט וחרא מכונאי
  • keef66
    keef66 Posts: 13,123
    In that first photo the rear mech is being pulled so far back because the chain isn't stopping it. That's the shape it would assume if you removed the chain entirely; it's just the tension spring in the mech doing it's job.
    Unless the chain's not wrapped round a chain ring, that much slack suggests the chain's too long. What does it look like in the big chainring / small sprocket?
  • keef66
    keef66 Posts: 13,123
    I'd also suggest you need a longer loop of outer cable to the rear mech. Which will also probably mean a new inner cable too.
  • gingaman
    gingaman Posts: 576
    The 9lb sledge should sort it out
  • Ben6899
    Ben6899 Posts: 9,686
    edited February 2015
    Re the outer cable loop being too short, it doesn't appear to be located in the braze-on so that's probably a moot point.

    But it certainly looks like the chain is too long.

    FYI... in small/small, the rear mech will look very similar to in the first photo and you'll have about 15/20mm between the bottom chain run and the top jockey wheel. The rear mech will move to a position similar to the second photo, as you move up the block towards the spokes.
    Ben

    Bikes: Donhou DSS4 Custom | Condor Italia RC | Gios Megalite | Dolan Preffisio | Giant Bowery '76
    Instagram: https://www.instagram.com/ben_h_ppcc/
    Flickr: https://www.flickr.com/photos/143173475@N05/
  • seanoconn
    seanoconn Posts: 11,673
    gingaman wrote:
    The 9lb sledge should sort it out
    I'm considering the sledge :lol:
    Pinno, מלך אידיוט וחרא מכונאי
  • seanoconn
    seanoconn Posts: 11,673
    Seems ok in the big ring

    BA98A7FC-6C73-43C1-9532-73D40EEDA6B9_zpsdsimkvwz.jpg
    Pinno, מלך אידיוט וחרא מכונאי
  • Ben6899
    Ben6899 Posts: 9,686
    In big/small, the jockey wheels should sit vertically above/below each other. Chain looks too long.

    Is this the chain you were using prior to the crash? If so, it's odd this never presented itself as a problem (because I guess you'd struggle to run small/small+1 or small/small+2 which should be usable gears).

    In small/small does the chain rub on the mech?
    Ben

    Bikes: Donhou DSS4 Custom | Condor Italia RC | Gios Megalite | Dolan Preffisio | Giant Bowery '76
    Instagram: https://www.instagram.com/ben_h_ppcc/
    Flickr: https://www.flickr.com/photos/143173475@N05/
  • bondurant
    bondurant Posts: 858
    It still doesn't look like the cable is seated in the mech properly unless my eyes deceive me
  • keef66
    keef66 Posts: 13,123
    Now it's zoomed out I can see the rear mech outer cable isn't located in the braze-on on the chainstay.

    That of course doesn't affect the length of the chain...
  • bungalballs
    bungalballs Posts: 193
    seanoconn wrote:
    Seems ok in the big ring

    BA98A7FC-6C73-43C1-9532-73D40EEDA6B9_zpsdsimkvwz.jpg

    As above... Your cable outer has come out of the braze on. Therefore your cable will be slack and not tensioning the mech. Refit it and you will at least back to where you started before you started, even if the chain is too long.
  • earthvspace4XTuUWcX
    earthvspace4XTuUWcX Posts: 322
    Looks like the inner is not passing through the guide/cable stop on the chain stay!!
    Ah you just beat me too it :)
  • Barbarossa
    Barbarossa Posts: 248
    Looks like the b-screw (I'm presuming that SRAM have them) has come off its stop. Loosen the bolt that holds the deraileur to the frame, rotate the body backwards and tighten it up again. If you're lucky, this will sort it out. If you're not, you will need a new derailleur and/or hanger.
  • cswitch
    cswitch Posts: 261
    Take it to a good bike shop when theyre not so busy, get the mechanic to explain to you what he is doing. Also get him to show you how to set up front and rear mech. Tip him, money well spent. Do it yourself next time.

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