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  1. #1
    Canadian Chick Aquakitty's Avatar
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    No happy medium with front derailleur on this bike!

    This is driving me crazy.

    I have a dj style bike with only the bottom and middle front ring in use. The top ring is a chainring guard. I had to replace the bottom bracket and the crankset. The old BB was an Octalink 118 mm with matching crankset. The new setup is a square taper crank 113mm with matching crankset. The chainline seems fine, the middle of the rear 8 speed cassette lines up with the middle chainring, plus I did a bunch of calculations to make sure it was correct.

    Anyways, I have tried 2 different dérailleurs and I cannot get the chain to not rub on the last 3cogs of the cassette when in the small ring in the front, or vice versa. I would expect some rub on the small/small but it does this on the 6/7 gear as well. If I adjust it any more, it will rub on the top cogs. The current dérailleur is a 9 speed front. There is just no way I can set it up any nicer, it is perfectly in line and as low as it can go without smashing the chainring guard.

    Any idea what could be up here?
    I prefer Eau de Tri-flow. Seriously, that shiz smells good!

  2. #2
    coprolite fietsbob's Avatar
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    Inner 2 of 3 you actually need a longer BB rather than a shorter.
    the middle space between the 2 chainrings is chainline center on a double.

    you may need someone who can see 1st hand what you are talking about.

    I ran a 2 of 3 double in the 80's , no issues .. 52-36
    chainring guard just a bit bigger than the outside chainring..

    so FD height was about the same as if I had the 52t on the outside
    rather than the middle.
    Last edited by fietsbob; 05-14-12 at 11:59 AM.

  3. #3
    Canadian Chick Aquakitty's Avatar
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    Well the front chainrings are tiny MTB rings. All I should have to do in theory is stop it from shifting to the top ring.
    I prefer Eau de Tri-flow. Seriously, that shiz smells good!

  4. #4
    Senior Member
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    Quote Originally Posted by fietsbob View Post
    Inner 2 of 3 you actually need a longer BB rather than a shorter.
    the middle space between the 2 chainrings is chainline center on a double.
    This could be the problem, although I have run a triple as a double (inner-middle-bash) without changing the bottom bracket, and it was fine. Can you post photos?
    Steve

  5. #5
    Senior Member CACycling's Avatar
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    How many speeds is the cassette and what speed is the chain?

  6. #6
    bike whisperer Kimmo's Avatar
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    Sounds like your BB is a bit short.

    If you don't want to buy a longer one, you could try tweaking your derailleur cage (not easy to do right).

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