Front Derailleur height

The Rookie
The Rookie Posts: 27,812
edited August 2011 in MTB workshop & tech
Just finishing off my Retro Gary Fisher build, its running a cheap Shimano riveted chainset (21 speed) and an STX RC front mech (Don't have the part number right now), I set the height using the normal 1-2mm clearance between the outer face of the cage and the big ring, but as I select the largest ring at the front the inner face of the cage is fouling the middle ring, if I lift it high enough to clear the middle ring the outer cage clearance is about 7mm.

Photo's this evening (it was getting a bit dark last night!) and PN if they help, but any suggestions welcome!

Simon
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.

Comments

  • nicklouse
    nicklouse Posts: 50,675
    dont forget to include the ring sizes.

    but sounds like you also need to check the chain line (BB may be a bit short)-
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    Chainrings are 44/32/22 I believe (May be 42/32/22)....will check.

    I'm not sure how BB width affects it, if I fit a wider BB the cage has to move out further but to centre over the large ring the middle ring will be in the same place relative to the large ring and therfore still foul the cage!

    Simon
    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.
  • supersonic
    supersonic Posts: 82,708
    Front mechs run on a four bar link - the movement is not linear.

    Though sounds more like the mech is of poor design.
    GT ZASKAR CARBON TEAM

    VOODOO CANZO

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  • The Rookie
    The Rookie Posts: 27,812
    Movement isn't linear, no, (Obviously) but whichever way you move it (the guide part of the mech staying vertical) if its just above the big ring it will be fouling the middle won't it!

    Simon
    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.
  • supersonic
    supersonic Posts: 82,708
    Ah, I misunderstood what you were saying lol.

    New mech.
    GT ZASKAR CARBON TEAM

    VOODOO CANZO

    Come and see me at https://www.facebook.com/biketyke/
  • The Rookie
    The Rookie Posts: 27,812
    New Mech maybe, but as it's all straight why is it fouling, or is it possible its designed for a larger tooth jump than 10T (say a 22-38T double)? As it's an STX RC it seems a bit old for that!

    Simon
    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.
  • nicklouse
    nicklouse Posts: 50,675
    still waiting for the info I asked about.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    :lol: Bike at home, me at work, will get it as soon as!

    Simon
    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.
  • supersonic
    supersonic Posts: 82,708
    Yeah, I think you are on the right lines, were some odd combos back then of chainrings. Still, I have not seen this with STX RC, as most of their chainsets were standard.

    A little higher than the nominal 1-2mm can still work, I have had to set up many a little higher for the same reason. Could give it a go, see if it works I have even filed and bent cages before lol.
    GT ZASKAR CARBON TEAM

    VOODOO CANZO

    Come and see me at https://www.facebook.com/biketyke/
  • nicklouse
    nicklouse Posts: 50,675
    The Beginner wrote:
    :lol: Bike at home, me at work, will get it as soon as!

    Simon

    I am guessing 44-32-22.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    Good try, but its 42/32/22, chainline is 50mm (middle ring), STX RC front mech (FD-MC36).

    09082011034.jpg

    and with it held out as in when the outer ring is engaged
    09082011033.jpg

    Simon
    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.
  • nicklouse
    nicklouse Posts: 50,675
    ahhh I had a different image in my head.


    just to satisfy my curiosity.

    crank part number and Axel length.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    BB is a 68x118 UN54 clone, crankset PN is FC-TY40, crankset was OE fit on a Giant Rincon (with 118BB), I haven't a clue how I came by the STX front mech, it was in my 'Box'o'bits' and suits the Mid 90's GaryF well, although I have a 34.9mm clamp STX with shims to 31.8 I could use instead if I have to!

    Simon
    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.
  • nicklouse
    nicklouse Posts: 50,675
    Ok something aint right here,

    that Crank set should have a Chain Line of 47.5mm

    and that should be on a 122.5mm axle (maybe a 118mm one I am missing a bit of info) but it would give the results as seen.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    But changing the axle width won't change the foul as that relates purely to the relative positions of the inner face of the cage to middle ring and outer to the outer ring, you can move it closer or further out with the chainline but it won't change the foul at all.

    Simon
    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.
  • nicklouse
    nicklouse Posts: 50,675
    yep.

    it must be for a 48T set then that is the last thing that i can think of.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    OK, That's a pain as it suites the look of the bike really well! May use it on the double and bash Carrera where it won't be an issue (and it's lighter than the LX that is on there!) and use the 34.9 STX on the GF.

    Looking at the pic the lower curve of the outer cage is clearly larger diameter than the chainwheel (don't normally look at it on that view!)

    Thanks for the help.

    Simon
    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.
  • The Rookie
    The Rookie Posts: 27,812
    OK, plonked the 34.9mm clamp STX on this morning and it all fits fine, will sand down the top of the spacer shims to bare ally (from black) to make them less obvious visually and live with that!

    Simon
    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.

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