Advertise on Bikeforums.net



User Tag List

Results 1 to 7 of 7

Thread: Derailleur help

  1. #1
    Senior Member pedalpedalpedal's Avatar
    Join Date
    May 2009
    Location
    Vancouver
    Posts
    255
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Derailleur help

    1) I noticed that my chain is rubbing against the front derailleur cage when I'm on the largest & smallest cog + smallest chainring (on a double), as well as all the combinations on the largest chainring.

    I've fooled around w/ the front derailleur's (Ultegra) limit screws (which are not labelled so I'm not sure which is the low and high...) and I noticed that I could get it to not rub while on Largest Cog + Small Chainring, but then it would still rub when on a higher gear.

    I'm sure that the cage is aligned properly, and it's at an appropriate height.

    Any tips on how to adjust my front derailleur to stop the rubbing?

    2) While adjusting the rear derailleur it still occasionally skips (both up and down) one gear around the middle of the cassette. How can I remedy this? I've been messing around and I think I'm making it worse, and I'm at the point where it's just frustrating.

    Of course, I could always bring it to a shop and get them to fix it, but I'd rather save the money and try to learn to do it myself.

  2. #2
    Senior Member johnknappcc's Avatar
    Join Date
    Feb 2009
    Location
    Columbus, OH
    My Bikes
    A beautiful columbus steel frame, 1986 Schwinn Voyageur touring bike, Currently Undergoing Overhaul
    Posts
    910
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    As long as I'm reading this correctly . . .

    You are cross-chaining, or at least partially.

    Make sure (with limit screws) that the front der. doesn't rub in these combos:
    small (chainring) / big (cog) and big (chainring) / small (cog)

    From there . . .

    If you get rub towards the last few cogs (in either direction) that means you should either trim the FD or switch chainrings. For example, if you hit an incline go down to the small chainring and then find the right cog in the back, instead of trying to hit the biggest cog in the back while still on the big chainring, and vice versa.

    On 2, sounds like too much tension in the der wire, screw in your barrell adjusters, and start from the beginning. Check this out . . . http://bicycletutor.com/adjust-rear-derailleur/ and go from there

  3. #3
    Great State of Varmint Panthers007's Avatar
    Join Date
    Sep 2008
    Location
    Dante's Third Ring
    Posts
    7,481
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Some combinations are going to rub regardless. At least that's the gist of what Shimano is trying to get across in this enclosure that comes with their derailleurs. This isn't very clear, but...

    Last edited by Panthers007; 06-10-09 at 11:07 AM. Reason: Sp.
    How do you keep an idiot in suspense?

  4. #4
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    20,651
    Mentioned
    46 Post(s)
    Tagged
    1 Thread(s)
    If you're riding with a Shimano indexing front derailleur, adjust the limits for effective shifting and optimum position in the gear combinations you expect to ride in, usually the mid to outer cassette cogs on the outer, and mid to inner cassette cogs on the inner.

    The cage should be wide enough to accomodate most combinations without rubbing, but will rub on highly crossed combinations when the chain comes at an extreme angle. Not an issue, since crossed combinations are more inefficient and should be avoided.

    If you're riding a system that allows the FD to be trimmed, (Campy, Sram) set the limits for good shifting and trim using the outer/outer & inner/inner combinations, then use the ability to trim to eliminate chain rub if and when it occurs.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  5. #5
    Great State of Varmint Panthers007's Avatar
    Join Date
    Sep 2008
    Location
    Dante's Third Ring
    Posts
    7,481
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Just the minor cable-stretch, once you have torqued-down the pinch-bolt holding the cable to the FD*, is enough to make the FD rub where it wasn't before. I find this especially true with triples. Then you can either release the pinch-bolt and yank the cable tighter again - which is likely to cause fraying and generally compromise your new cable. Or you can do what I just did with a triple/cable set-up that was driving me nuts.

    I installed a barrel-adjuster on the cable.. A 1/4 turn solves the problem, or thereabouts.

    * Usual recommended torque is 48 - 60psi.

    How do you keep an idiot in suspense?

  6. #6
    cab horn
    Join Date
    Jun 2004
    Location
    Toronto
    My Bikes
    1987 Bianchi Campione
    Posts
    28,295
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    On an ultegra front derailleur you should be able to eliminate the rub on large chainring, smallest cog. Follow the F.D adjustment proceudre on parktool, and report the results. Hell, i've gotten extremely acceptable front shifting on a piece of **** Shimano C101 front derailleur on a piece of crap generic triple crankset with nary extra work.

    http://www.parktool.com/repair/readhowto.asp?id=75
    Mes compaingnons cui j'amoie et cui j'aim,... Me di, chanson.

  7. #7
    Senior Member
    Join Date
    Feb 2005
    Location
    Oklahoma
    My Bikes
    Trek 5500, Colnago C-50
    Posts
    9,093
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Use the instructions at the Parktool site offered above by operator. Do each step in proper sequence leaving nothing out.

Posting Permissions

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