Advertise on Bikeforums.net



User Tag List

Results 1 to 6 of 6
  1. #1
    Canadian Chick Aquakitty's Avatar
    Join Date
    Jun 2009
    Location
    BC, Canada
    My Bikes
    Lots
    Posts
    628
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    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?

  2. #2
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    3,219
    Mentioned
    47 Post(s)
    Tagged
    0 Thread(s)
    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 12:59 PM.

  3. #3
    Canadian Chick Aquakitty's Avatar
    Join Date
    Jun 2009
    Location
    BC, Canada
    My Bikes
    Lots
    Posts
    628
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    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.

  4. #4
    Senior Member
    Join Date
    Aug 2005
    Location
    Hudson Valley, NY
    Posts
    246
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    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
    Join Date
    Feb 2008
    Location
    Oxnard, CA
    My Bikes
    '08 Fuji Roubaix RC; '07 Schwinn Le Tour GS; '92 Diamond Back Ascent EX
    Posts
    4,449
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    How many speeds is the cassette and what speed is the chain?

  6. #6
    bike whisperer Kimmo's Avatar
    Join Date
    Dec 2009
    Location
    Melbourne, Oz
    My Bikes
    copy/paste links: http://velospace.org/node/36949 http://velospace.org/node/47746 http://velospace.org/node/47747
    Posts
    6,842
    Mentioned
    10 Post(s)
    Tagged
    0 Thread(s)
    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).

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •