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Chain sizing query

  • 06-05-2011 11:56am
    #1
    2wheelsbetter
    Registered Users, Registered Users 2 Posts: 38 ✭


    Hey,

    I've got two cassettes that I'd like to swap out depending on my intended cycle. For one of them the largest sprocket is 22 and on the other it's 28. I have a couple of quick links so I could size two chains with each suitable for one of the cassettes. However, I'd rather not. What would the disadvantages be to sizing the chain to suit somewhere in between the two cassettes i.e. a little too big for the 22T cassette and little too small for the 28T cassette?

    Thanks.


Comments

  • #2
    cython
    Registered Users, Registered Users 2 Posts: 4,792 ✭✭✭cython


    2wheelsbetter wrote: »
    Hey,

    I've got two cassettes that I'd like to swap out depending on my intended cycle. For one of them the largest sprocket is 22 and on the other it's 28. I have a couple of quick links so I could size two chains with each suitable for one of the cassettes. However, I'd rather not. What would the disadvantages be to sizing the chain to suit somewhere in between the two cassettes i.e. a little too big for the 22T cassette and little too small for the 28T cassette?

    Thanks.

    Are the smallest sprockets on each cassette the same? If so then you should (assuming that your derailleur has sufficient capacity for the chain slack) at least avoid an issue whereby when in the small front/small back the rear mech is able to move too far backwards, and the chain rubs itself due to it being too long/excessive chain slack.

    The Park Tool page on the subject seems to suggest that sizing it according to the big chainring-big sprocket (the 28T in your case) test, and then having the rider avoiding combinations that result in excessive chain slack (as might happen with the smaller cassette) would be best.

    Logically though, it seems to me that if the range of your smaller cassette is within that of the larger one (e.g. 11-22 would be within 11-28), then sizing for the 28T should be fine, as the setup would have to accomodate the same/similar combinations anyway, provided that the mech, etc, can accommodate all the difference in sizes in the wider range cassette. Your chain might just never completely eliminate slack with the smaller cassette. I am open to correction on this though.


  • #3
    C3PO
    Registered Users, Registered Users 2 Posts: 3,795 ✭✭✭C3PO


    Much better to have 2 seperate chains! A chain that's too long will slap around the place and one that's too short could lead to nasty consequences if for example you try to shift to big/big! Also the chain and cassette will wear together if they're matched so probably cheaper in the long run too!


  • #4
    Holyboy
    Registered Users, Registered Users 2 Posts: 869 ✭✭✭Holyboy


    RPL1 wrote: »
    Much better to have 2 seperate chains! A chain that's too long will slap around the place and one that's too short could lead to nasty consequences if for example you try to shift to big/big! Also the chain and cassette will wear together if they're matched so probably cheaper in the long run too!

    I agree,a chain for every cassette other wise you will run into wear problems but I have to say running two or three chains in rotation on a single cassette prolongs the life hugely,but if your hell bent on one chain the same length will do both cassette ratios,sram recommend you put the chain on large/large without going through the mech and then adding one full link,kmc say fit chain through the mechs go small/small and join the chain so its as close to but not touching the rear mech,thats the way I do it too:)


  • #5
    2wheelsbetter
    Registered Users, Registered Users 2 Posts: 38 ✭2wheelsbetter


    Thanks lads.
    cython wrote: »
    Are the smallest sprockets on each cassette the same?
    The smallest sprockets are both 11T.
    RPL1 wrote: »
    Much better to have 2 seperate chains! A chain that's too long will slap around the place and one that's too short could lead to nasty consequences if for example you try to shift to big/big! Also the chain and cassette will wear together if they're matched so probably cheaper in the long run too!
    That was something that had me worried. I was thinking of leaning towards as small a chain I could get away with to accommodate this larger cassette. As for keeping the chain at this but switching out the cassette I was wondering if the RD would pick up the slack. I'd imagine that, given that both of the cassettes have an 11T sprocket as their smallest, that the larger chain length should work for both cassettes. When the chain is on the smallest sprocket at the back the RD isn't to know which cassette is on the wheel. (I think that this is what cython was getting at?)


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