Results 1 to 8 of 8
  1. #1
    RoadBikeReview Member
    Reputation:
    Join Date
    Apr 2014
    Posts
    129

    Chain sizing question

    My friends new bike has mid-compact gearing 52/36 but most of his commutes are dead flat. So he wants to install a 42 to replace the 36 for flat rides but have the option of switching back to the 36 for hillier rides. Current cassette is 11-28 but he wants to get several cassettes for different terrain for the other wheels when he needs to switch.

    The 2 he wants to get are 12-25 & a 11-30. So the question is will his present chain work without any changes when he switches over to the 42?

  2. #2
    xxl
    xxl is offline
    Moderator
    Reputation: xxl's Avatar
    Join Date
    Mar 2002
    Posts
    30,527
    It depends on the "wrap" capacity of his derailleur--basically, long-cage ones have the capability to wrap up more extra chain.

    Re your friend going to a 42 for commutes, there's no problem, since the bike's already set up for 52 down to 11--i.e., it can handle gears within that interval. Ditto for the 12-25 cassette, it's within your current gearing. Without knowing more about the derailleur one can't be certain, but two-teeth shouldn't be a problem.
    More Americans wanted Hillary Clinton to be President than wanted Donald Trump.

  3. #3
    Forever a Student
    Reputation: MMsRepBike's Avatar
    Join Date
    Mar 2014
    Posts
    4,741
    Install the 11-whatever cassette.

    Install the smallest chainring.

    Install a chain with the small/small method. (who knows hows it's done now, so do it again the right way)

    This will make the chain as long as possible but within proper spec for the mech, it will give it the best chance of fitting everything. In this case it should be fine.
    use a torque wrench

  4. #4
    tlg
    tlg is offline
    RoadBikeReview Member
    Reputation: tlg's Avatar
    Join Date
    May 2011
    Posts
    10,240
    Quote Originally Posted by stan01 View Post
    So the question is will his present chain work without any changes when he switches over to the 42?
    The only person who knows that is the person who installed the present chain. And there's a high probability that person doesn't know.

    Follow MMsRepBike's advice and size the chain using the small/small method (which is the best way to size the chain anyway). It guarantees the longest chain possible.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

  5. #5
    RoadBikeReview Member
    Reputation:
    Join Date
    Apr 2014
    Posts
    129
    The rear mech is the new Dura Ace 9100 & it was sized big/big according to Shimano's guidelines. That's why we are having this debate.

  6. #6
    tlg
    tlg is offline
    RoadBikeReview Member
    Reputation: tlg's Avatar
    Join Date
    May 2011
    Posts
    10,240
    Quote Originally Posted by stan01 View Post
    The rear mech is the new Dura Ace 9100 & it was sized big/big according to Shimano's guidelines. That's why we are having this debate.
    Shimano's got it wrong. Unless of course their goal is to sell more chains... and broken RD's. The only way the big/big sizing method works is if you start with the max sized gears and would only ever go smaller.

    Going to the 42 chainring will be no problem. Going to an 11-30 cassette will probably tear off the RD when going into the big/big.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

  7. #7
    RoadBikeReview Member
    Reputation: bikerjulio's Avatar
    Join Date
    Jan 2010
    Posts
    7,358
    The small-small method guarantees things will work fine until your friend runs out of RD capacity, at which point bad things may happen.

    A 52/36 combined with a 11-30 requires 35T of capacity which exceeds the 33T spec capacity of a current Shimano short cage. Maybe it will work, but it requires very careful chain sizing and checking.

    Medium cage would be no problem.
    Last edited by bikerjulio; 06-23-2017 at 05:46 AM.
    We just don’t realize the most significant moments of our lives when they’re happening
    Back then I thought “well there'll be other days”
    I didn’t realize that was the only day
    https://www.youtube.com/watch?v=Y9yrupye7B0

    There's sometimes a buggy.
    How many drivers does a buggy have?
    One.
    So let's just say I'm drivin' this buggy...
    and if you fix your attitude you can ride along with me.
    http://www.youtube.com/watch?v=GekiIMh4ZkM

  8. #8
    RoadBikeReview Member
    Reputation:
    Join Date
    Apr 2014
    Posts
    129
    The bike was built by him & he asked me for advice during its build. I advised him to use small/small but I also told him to follow the manufacturer's guidelines since I wasn't familiar with the new 9100 groupset.

    And that is what he did, followed Shimano's guidelines & sized it big/big using the 11-28. Now that its built, he knows he wants more gearing options as he keeps mentioning the possibility of a 11-32 Ultegra instead of the Dura Ace 11-30. I guess I'll tell him that he's going to need a new chain as well if he wants that gearing.

Similar Threads

  1. Chain sizing question
    By Fireform in forum Components, Wrenching
    Replies: 4
    Last Post: 09-09-2013, 08:30 AM
  2. Chain, chain, chain...
    By brujenn in forum The Lounge
    Replies: 1
    Last Post: 07-30-2009, 05:59 AM
  3. Euro Sizing vs. USA Sizing
    By coltrane in forum Bikes, Frames and Forks
    Replies: 2
    Last Post: 03-27-2006, 07:19 AM
  4. internet sizing vs. LBS sizing ????
    By jsmst33 in forum Bikes, Frames and Forks
    Replies: 8
    Last Post: 09-08-2004, 02:05 PM
  5. Roadie sizing vs. MTB sizing...
    By slowride in forum Bikes, Frames and Forks
    Replies: 1
    Last Post: 06-07-2004, 08:49 AM

Posting Permissions

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