Advertise on Bikeforums.net



User Tag List

Results 1 to 10 of 10
  1. #1
    Newbie
    Join Date
    Feb 2008
    Location
    Cupertino, CA
    My Bikes
    2009 BMC SLT01, 2009 Trek District, Broken 2006 Orbea Opal :(
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Swapping different sized chainrings

    I'm looking to swap out some 175 FSA SLK cranks I have for 172.5 FSA cranks that I found a good deal on. My 175 is 46/36 and the 172.5 cranks have 52/38. Both have a BCD of 110 so are the two chainrings interchangeable? I'm looking to keep the 38 on the 172.5 cranks, but swap over the 46 from the 175 cranks to the 172.5 cranks so in the end I'd have 46/38. I feel like swapping over shouldn't be an issue, but I'm not 100% so I figured I'd ask.

  2. #2
    Senior Member ScottNotBombs's Avatar
    Join Date
    Mar 2008
    Location
    Joliet, IL
    Posts
    405
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It'll be fine, just move your derailleur down so there's a 1mm gap between the cage and new chain ring.
    I'm just a kid who gets in trouble sometimes

  3. #3
    Newbie
    Join Date
    Feb 2008
    Location
    Cupertino, CA
    My Bikes
    2009 BMC SLT01, 2009 Trek District, Broken 2006 Orbea Opal :(
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Awesome, thanks for the quick reply.

  4. #4
    Constant tinkerer FastJake's Avatar
    Join Date
    May 2010
    Location
    Madison, Wisconsin
    Posts
    6,120
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    It'll be fine. Any reason why you want such a close ratio up front? Just curious..
    Why "derailer" is the correct way to spell the gear-change mechanism: sheldonbrown.com/derailer.html

  5. #5
    Gear Combo Guru Chris_W's Avatar
    Join Date
    May 2007
    Location
    Switzerland
    My Bikes
    Spec' Tarmac (road), Spec' Secteur Disc (commuter & tourer), Salsa Mamasita (MTB), CoMo Speedster (tandem), Surly Big Dummy (cargo), Airnimal (folder), a train pass, and NO car :)
    Posts
    2,046
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Agreed that the chainring swap will be fine. Plus, there may be no need to move the front derailleur. If I understood you correctly, the large ring is going to stay the same (46 teeth), and it is that normally determines the front derailleur position. Try it as it is, and only if the inner cage of the FD contacts the inner chainring when you try to shift to the big ring, then move it up, but if it doesn't then leave it.
    Last edited by Chris_W; 03-13-11 at 08:51 AM.

  6. #6
    Certified Bike Brat Burton's Avatar
    Join Date
    Jan 2011
    Location
    Montreal, Quebec
    Posts
    4,203
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Another confirmation

    An easy switch and no reason to change the position of the front derailleur. Correct installation requires a 2mm clearance between the large chainring and the ouside face of the front derailleur as it passes over it.

    Since your large chainring will remain unchanged the front derailleur calibration should be unaffected.

  7. #7
    Senior Member ScottNotBombs's Avatar
    Join Date
    Mar 2008
    Location
    Joliet, IL
    Posts
    405
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Oops. I didn't realize he was changing the smaller chainring.. On the park website it says 1-2mm or about the thickness of a penny
    I'm just a kid who gets in trouble sometimes

  8. #8
    Senior Member Kevinative's Avatar
    Join Date
    Jan 2011
    Location
    Cherry Hill, NJ
    My Bikes
    GF Level Betty FHO, GF Paragon, Raleigh Tomac, DB Interval, Scott CR1 Team
    Posts
    76
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    ok so I did the search function to avoid starting a new thread. I've got a slightly different angle on this same question. My new carbon bike (CR1) came with a CD, 50/34. I recently purchased an older 105 octalink crankset that has a 53/43. I want to simply put the 53/43 rings on the new crankset. both are 105, don't see any fit issue, may have to slightly raise fr der. question is, what about chain length? are 3 extra teeth going to require an extra link?

  9. #9
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    38,912
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)
    Probably.. may be time to put on a fresh chain anyhow..

  10. #10
    Newbie
    Join Date
    Feb 2008
    Location
    Cupertino, CA
    My Bikes
    2009 BMC SLT01, 2009 Trek District, Broken 2006 Orbea Opal :(
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Kevinative View Post
    ok so I did the search function to avoid starting a new thread. I've got a slightly different angle on this same question. My new carbon bike (CR1) came with a CD, 50/34. I recently purchased an older 105 octalink crankset that has a 53/43. I want to simply put the 53/43 rings on the new crankset. both are 105, don't see any fit issue, may have to slightly raise fr der. question is, what about chain length? are 3 extra teeth going to require an extra link?
    Just an update, everything worked out well on my end. But for you, I feel like you're in the same position I was in. 53 tooth rings only fit on BCD 130 spacing cranks so they wouldn't fit on a BCD 110, which is compact.

Posting Permissions

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