Advertise on Bikeforums.net



User Tag List

Results 1 to 5 of 5
  1. #1
    . bormoglot's Avatar
    Join Date
    Aug 2005
    Posts
    133
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    FD adjustment going from 52/42/30 to 48/39/26

    I am going to modify one of my road bikes (mostly Tiagra components) by putting smaller chainrings. Currently I have road 52/42/30 (130/74bcds) and I've already sourced appropriate 48/39/26 chainrings.

    Now, the question is how exactly do I need to adjust FD? Do I really need to move it lower on the seat tube? Do I need to cut the chain? Anything else to pay attention to?

  2. #2
    Senior Member bikeman715's Avatar
    Join Date
    Mar 2008
    Location
    Salinas , Ca.
    My Bikes
    Bike Nashbar AL-1 ,Raligh M50 , Schwinn Traveler , and others
    Posts
    1,984
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    yes lower the FD to where it would be 2 mm above the big chain rings 48 and you might to shorten the chain too . you might need to readjust the FD because your new crank set may change your chain line .

  3. #3
    Senior Member Bill Kapaun's Avatar
    Join Date
    Feb 2007
    Location
    Mid Willamette Valley, Orygun
    My Bikes
    86 RockHopper,2008 Specialized Globe. Both upgraded to 9 speeds.
    Posts
    6,754
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Most likely, the FD will work better if you move it down.
    Your current steps between rings (B>S) is- 10-12
    The replacement will be 9-13, or less "linear".
    This will probably result in shifting being less "precise".
    Also, the "radius" of the FDER will mismatch the radius of the rings a bit more.
    It should work, but be less smooth.
    Don't be afraid to experiment with other than the so called "ideal" clearance above the big ring. I've had one FDER actually work noticeably better when the height was higher than "ideal".

    Once you decide that you are going to keep that set up, I'd trim the chain to match.

  4. #4
    Senior Member
    Join Date
    Feb 2005
    Location
    Oklahoma
    My Bikes
    Trek 5500, Colnago C-50
    Posts
    9,016
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    If the front derailleur is a "braze-on" type you may not be able to lower it far enough without some creative grinding and filing. The replacement rings will work better if they are designed to work in a triple, the middle ring needs ramps and pins to assist with the shifting. I replaced the 52-42-30 rings on my wife's Ultegra triple with TA Alize 49-39-28 rings (notice the nearly even tooth count jumps) and these required lots of tweaking and adjusting to make them shift right. It's likely that you will lose some shifting smoothness when changing chainrings, especially on a triple.
    After lowering the front derailleur you will definitely need to re-adjust it. Lowering it puts slack in the cable. Follow the adjustment proceedures found at http://www.parktool.com.
    You may need to shorten the chain to keep it from going slack if you accidentally shift into the small to small combination.

    Al

  5. #5
    . bormoglot's Avatar
    Join Date
    Aug 2005
    Posts
    133
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Al1943 View Post
    The replacement rings will work better if they are designed to work in a triple, the middle ring needs ramps and pins to assist with the shifting.
    Yes, they are designed to work in the triple. 48 and 39 are from FSA, and while majority of FSA's 39 are for doubles (no pins and ramps) some FSA's 39 are for triples. TA manufacture nice rings, but they are a bit pricey... FSA is more than twice cheaper.

Posting Permissions

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