Tiagra B screw issues - Huge gap

richy945
richy945 Posts: 8
edited December 2016 in Workshop
I've just built up an old Giant defy using a Tiagra 4600 short derailleur. The problem is the gap between the jockey wheel and the sprocket is far too great even with the B screw wound all the way out. :S I'm really stumped. Please see photo Rcdny

I've fitted an 11-25 cassette and 53/39 chainrings. I'm having poor shifting issues and wondering if this could be it? Any ideas? Thanks

Comments

  • jermas
    jermas Posts: 484
    Can't see image, but have you checked the chain length is correct? Is the final loop of cable that runs to the derailleur long enough? Also check the top derailleur pivot (that mounts to the hanger) moves freely and is mounted correctly.
  • arlowood
    arlowood Posts: 2,561
    jermas wrote:
    Can't see image, but have you checked the chain length is correct? Is the final loop of cable that runs to the derailleur long enough? Also check the top derailleur pivot (that mounts to the hanger) moves freely and is mounted correctly.

    Here is the image for those that can't see it

    jCMdtht.jpg
  • jermas
    jermas Posts: 484
    That's better cheers. It looks like the cable is mounted incorrectly -which would explain the poor shifting. The cable has to sit in the groove and sit straight (as apposed to around the clamp bolt).
  • richy945
    richy945 Posts: 8
    jermas wrote:
    That's better cheers. It looks like the cable is mounted incorrectly -which would explain the poor shifting. The cable has to sit in the groove and sit straight (as apposed to around the clamp bolt).

    Thanks, that's definitely helped with my shifting issue, I don't really have an excuse for that :roll: However I'm still stumped with the b screw. I wonder if it would work better with an 12-27 cassette instead ?
  • keef66
    keef66 Posts: 13,123
    Which chainring was it in when you took the pic? If it was the big one I'd expect the mech to be pulled further forward than that, which suggests the chain's too long?

    If the small ring, ignore.
  • richy945
    richy945 Posts: 8
    keef66 wrote:
    Which chainring was it in when you took the pic? If it was the big one I'd expect the mech to be pulled further forward than that, which suggests the chain's too long?

    If the small ring, ignore.

    It was in the small ring. Chain length I think is good. I have mimicked shortening the chain and it has no effect on the distance between the jockey wheel and sprocket.

    It's hard to explain but when it is in the position like the picture there is no spring tension on the mech, you can just move it closer to the sprocket and it will stay wherever you leave it. It just sits in the photo position naturally after shifting. I hope that makes some sort of sense ?
  • keef66
    keef66 Posts: 13,123
    Sounds like the spring's broken or unseated somehow? Or is it possible the entire cage has rotated 360 deg so the spring's under little / no tension? Is that even possible?? Has the cage ever been removed from the mech?
  • The Rookie
    The Rookie Posts: 27,812
    There is a spring missing from the cable adjuster as well, the black plastic should be up against the mech!
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • richy945
    richy945 Posts: 8
    The Rookie wrote:
    There is a spring missing from the cable adjuster as well, the black plastic should be up against the mech!

    That would explain why I found a spring on my garage floor :roll: So the ferrel from where the cable enters the barrel adjuster should go hard up against the spring ?
  • The Rookie
    The Rookie Posts: 27,812
    No, the spring goes between the steel part of the adjuster and the plastic part, it pushes the plastic against the body so that the detente work.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • pilot_pete
    pilot_pete Posts: 2,120
    Shimano website has all the tech documents which include dealer manuals with instructions for installation and adjustment etc for each component. I think this is the manual that covers your derailleur;

    http://si.shimano.com/php/download.php?file=pdf/dm/DM-GN0001-18-ENG.pdf

    Mind you, Ribble are selling that derailleur for £15 so that would be a simple and cheap fix if something has broken Spring wise...
    http://www.ribblecycles.co.uk/shimano-tiagra-4600-10-spd-rear-gear/

    PP
  • Bobbinogs
    Bobbinogs Posts: 4,841
    Buy a new derailleur, ask a bike shop to fit it. Then have a good look at it afterwards. The £35 spent will be a good investment.

Categories