Chain Length Question

Discussion in 'Cycling Equipment' started by rickn, Jun 1, 2004.

  1. rickn

    rickn Guest

    Hello:
    I am in the middle of a double to triple crankset upgrade which, among
    other things, includes a new rear "long" derailleur, and a new chain.
    How do I determine the correct chain length?
    Thanks,
    Rick
     
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  2. Michael Dart

    Michael Dart Guest

    In news:[email protected],
    rickn <rickn> typed:
    > Hello:
    > I am in the middle of a double to triple crankset upgrade which, among
    > other things, includes a new rear "long" derailleur, and a new chain.
    > How do I determine the correct chain length?
    > Thanks,
    > Rick


    It's still measured around the big cog and big ring (not through rear
    derailleur) plus about 2 links. This measurement get's a little more
    complicated with suspension but it sounds like you have a road bike. Your
    original chain length should work if you aren't changing the size of the big
    cog/rings. The long cage derailleur will take up the slack when you are in
    your granny gear.

    Mike
     
  3. Rick Onanian

    Rick Onanian Guest

    On Tue, 1 Jun 2004 07:07:06 -0400, rickn <rickn> wrote:
    >How do I determine the correct chain length?


    You want the shortest length that will run in the big-big gear
    combination. Maybe add a couple links (it is easier to remove them)
    in case you change your gearing in the future.
    --
    Rick Onanian
     
  4. > How do I determine the correct chain length?

    The formula I learned many years ago is easier to do than it is to describe:

    Measure the distance in inches from the centre of the spindle [at the
    dustcap] to the centre of the rear axle. Multiply that distance by two,
    and round the product up to the next whole inch. Call this number A.

    Add the number of teeth on the largest chainwheel to the number of teeth
    on the largest sprocket. If that sum is odd, add one to get an even
    number. Divide the resulting sum by two. If that quotient is odd, add
    one to get an even number. Again divide the result by two, and call the
    final quotient B.

    Add the numbers A and B and one to get the chain length you need.

    For example, one of my bikes has a centre-to-centre distance from the
    spindle to the rear axle of 17-3/4 inches. Multiply by two and get 35.5,
    so A is 36 [the next whole number].

    The largest chainwheel has 53 teeth, and the largest sprocket has 28, so
    their sum is 81. This is an odd number, so add one to get 82. Divide 82
    by two to get 41. This is another odd number, so add one to get 42.
    Divide 42 by two to get 21, so B is 21.

    Adding A and B and one, I get 36 + 21 + 1 = 58 inches of chain.
     
  5. Jpinkowish

    Jpinkowish Guest

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