Advertise on Bikeforums.net



User Tag List

Results 1 to 13 of 13

Thread: Chain Length

  1. #1
    AJU
    AJU is offline
    Senior Member
    Join Date
    Aug 2006
    Posts
    149
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Chain Length

    I have read Sheldon Brown's writeup on chain length (1 link beyond meeting around the biggest ring/cog), but have a question he didn't answer. What if I want to swap cassettes? How can I acheive a functional compromise? For example, I have a 48t large ring. I have a cassette with a 25 large cog and I have a cassette with a 32t large cog. Is there any way I can size the chain so I can use either cassette without modifying the length of the chain?

  2. #2
    Sometimes knows stuff. rmfnla's Avatar
    Join Date
    May 2005
    Location
    La La Land (We love it!)
    My Bikes
    Gilmour road, Curtlo road
    Posts
    2,538
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Probably not. Either too much or too little chain will cause shifting problems.

    This is why multi-speed bikes exist, so you can have a range of gears. If you are going to need (or want) a 32 bottom end then get that and set your bike up for it correctly.
    Today, I believe my jurisdiction ends here...

  3. #3
    .
    Join Date
    May 2006
    Location
    Hillsboro, Oregon
    My Bikes
    Moots Psychlo-x ybb, Soma ES, Trek 950
    Posts
    3,783
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    What about on the other end? What do you have on the high end of the cassette? I would think that if both cassettes have the same, or close to, high gearing, then it would work. A 32/12 and a 25/11 might work, I would think.
    Demented internet tail wagging imbicile.

  4. #4
    Sometimes knows stuff. rmfnla's Avatar
    Join Date
    May 2005
    Location
    La La Land (We love it!)
    My Bikes
    Gilmour road, Curtlo road
    Posts
    2,538
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by knobster View Post
    What about on the other end? What do you have on the high end of the cassette? I would think that if both cassettes have the same, or close to, high gearing, then it would work. A 32/12 and a 25/11 might work, I would think.
    No.

    The chain is cut to work with the largest ring & cog; the small cogs don't influence this process.
    Today, I believe my jurisdiction ends here...

  5. #5
    Senior Member Retro Grouch's Avatar
    Join Date
    Feb 2004
    Location
    St Peters, Missouri
    My Bikes
    Rans Enduro Sport, Hase Kettweisel Tandem, Merin Bear Valley beater bike
    Posts
    23,975
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Not an issue.

    Assuming your rear derailleur has the slack take up capability to handle the 32t cassette, just size it for that cassette and it'll work with the smaller one too.

    If your derailleur doesn't have enough slack take up, I still think that it's better to size it for the largest possible combination. You might have some issues with the little/little combinations but those seldom come up when using a double crankset and they never come up with a triple.

  6. #6
    AJU
    AJU is offline
    Senior Member
    Join Date
    Aug 2006
    Posts
    149
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    It's a long cage XTR - I imagine it has enough take up

  7. #7
    Gone, but not forgotten Sheldon Brown's Avatar
    Join Date
    Jul 2002
    Location
    Newtonville, Massachusetts
    My Bikes
    See: http://sheldonbrown.org/bicycles
    Posts
    2,301
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by AJU View Post
    I have read Sheldon Brown's writeup on chain length (1 link beyond meeting around the biggest ring/cog), but have a question he didn't answer. What if I want to swap cassettes? How can I acheive a functional compromise? ... I have a cassette with a 25 large cog and I have a cassette with a 32t large cog. Is there any way I can size the chain so I can use either cassette without modifying the length of the chain?
    Size it to the largest combo.

    Sheldon "Too Long Is Harmless" Brown
    [COLOR=blue][CENTER][b]Harris Cyclery, West Newton, Massachusetts[/b]
    Phone 617-244-9772, FAX 617-244-1041
    [URL= http://harriscyclery.com] http://harriscyclery.com[/URL]
    Hard-to-find parts shipped Worldwide
    [URL=http://captainbike.com]http://captainbike.com[/URL]
    Useful articles about bicycles and cycling
    [URL=http://sheldonbrown.com]http://sheldonbrown.com[/URL] [/CENTER] [/COLOR]

  8. #8
    AJU
    AJU is offline
    Senior Member
    Join Date
    Aug 2006
    Posts
    149
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thank you!

  9. #9
    Senior Member
    Join Date
    Aug 2005
    Location
    Pittsburgh, PA
    My Bikes
    '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
    Posts
    26,143
    Mentioned
    13 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Sheldon Brown View Post
    Size it to the largest combo.

    Sheldon "Too Long Is Harmless" Brown
    I wish we could get that idea across. For some reason so many riders thing a too long chain is as harmful as a too short one.

  10. #10
    Mechanic/Tourist
    Join Date
    Apr 2007
    Location
    Syracuse, NY
    My Bikes
    2008 Novara Randonee - love it. Would have more bikes if I had time to ride them all. Previous bikes: 1968 Motobecane Mirage, 1972 Moto Grand Jubilee (my fav), Jackson Rake 16, 1983 C'dale ST500.
    Posts
    5,357
    Mentioned
    8 Post(s)
    Tagged
    0 Thread(s)
    Indeed it's silly to say "It won't work" with the smaller range cassette, considering that a 25 tooth cog (or close) would be on the large range cassette. As long as the derailleur will handle the 32 you will have no problems. I went on a tour on a freewheel with a 28 larg cog, and changed to a 13-21 for a couple of races - ran great.

  11. #11
    Title-Les
    Join Date
    Feb 2007
    Posts
    172
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Since the OP's question appears well-answered perhaps it won't be thread-stealing for me to mention something I developed for switching around cogs on my Sturmey Archer 3-speeders. I cut my chain deliberately short and then make up a short (maybe less than 6" worth) splicing length of chain to bring the total length of the long section added with the "splice" section to the correct length for the particular cog. The 18T cog and the 22T cog each has its own different-length "splice" section. Of course this uese two master links and in the case of one of the two sets, a half-link IIRC.

    So when I change from one cog to the other, I also change splice sections.

    Geeze, I hope I explained that OK.
    alf

  12. #12
    Sometimes knows stuff. rmfnla's Avatar
    Join Date
    May 2005
    Location
    La La Land (We love it!)
    My Bikes
    Gilmour road, Curtlo road
    Posts
    2,538
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by HillRider View Post
    I wish we could get that idea across. For some reason so many riders thing a too long chain is as harmful as a too short one.
    Well, neither is really "harmful".

    To short can cause binding if you attempt to engage both large gears; too long can cause the cage to ride up on the cluster if you are in small-small.

    Yes, these gear combinations are not recommended; I'm just fussy and like my bikes to work as well as possible.
    Today, I believe my jurisdiction ends here...

  13. #13
    In beaurocratic limbo urbanknight's Avatar
    Join Date
    Mar 2006
    Location
    Los Angeles, CA
    My Bikes
    Specialized Allez, K2 Razorback
    Posts
    22,457
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by rmfnla View Post
    No.
    The chain is cut to work with the largest ring & cog; the small cogs don't influence this process.
    Quote Originally Posted by rmfnla View Post
    To short can cause binding if you attempt to engage both large gears; too long can cause the cage to ride up on the cluster if you are in small-small.
    Except if both cassettes have the same small cog, there's no such thing as a chain too long for one but not the other. "too long" depends on the small/small combination, while "too short" depends on the big/big. As mentioned above, a 12-34 cassette will include a 25 cog (or close to it), so if the chain and RD can handle the larger combination, the smaller one will be fine.

    Of course, we haven't heard yet if the smallest cogs are the same on both cassettes.
    "Well, I guess you can cut the arts as much as you want... Sooner or later, these kids aren't going to have anything to read or write about." (Richard Dreyfus as Glenn Holland)

Posting Permissions

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