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rear derailleur cage size

SproolSprool Posts: 1,022
edited February 2014 in Road buying advice
I have a canyon CF SL coming next week, 105 group set, compact 50/34 with 11-32 cassette on the back, so I'm assuming its a long cage derailleur - will this still work ok if I want to swap out to a tighter range cassette for flatter terrain, say 11-28 or 11-25?

Posts

  • DiscoBoyDiscoBoy Posts: 905
    Yes, but you'll need to shorten the chain.

    I'm half way through doing this myself actually (except with a BMC). The new cassette is on, and the. Chain is off ready to be shortened.
    Red bikes are the fastest.
  • SproolSprool Posts: 1,022
    How do you know how many links to remove?
    And when you change back to the wider cassette, can you get away with using a few of those power links to get back to original size?
  • DiscoBoyDiscoBoy Posts: 905
    Sprool wrote:
    How do you know how many links to remove?
    And when you change back to the wider cassette, can you get away with using a few of those power links to get back to original size?

    You can "get away with" using the same chain changing between cassettes with slightly different large cogs, but 25-32 isn't what I'd call slight.

    For the price of a 10 speed chain, I'd probably have a chain for each cassette. This is also a good idea because chains and cassettes wear (out) together- which is probably makes it a bad idea to use several power links to make the chain longer. A new chain is probably a comparable price to a few power links anyway.

    There are several ways of gauging how long to make a chain, you can find them easily with google.
    For my 12-25 I will be using this method:
    Thread chain through derailleurs
    Set gears to largest cog at front, smallest cog at rear (50-12)
    Set chain length so that, in this combination, the derailleur jockey wheels are vertical

    NB that this isn't the best way to do it for a cassette with more than about 27 teeth.
    Red bikes are the fastest.
  • mr_evilmr_evil Posts: 234
    You won't have to shorten the chain, since the smallest combination will remain 34/11 no matter which cassette you switch to. You could shorten it anyway to save a little weight, but I would recommend leaving it, so you can freely swap between cassettes.
  • lesfirthlesfirth Posts: 1,286
    Mr Evil wrote:
    You won't have to shorten the chain, since the smallest combination will remain 34/11 no matter which cassette you switch to. You could shorten it anyway to save a little weight, but I would recommend leaving it, so you can freely swap between cassettes.

    That's just what I thought. Can any of the chain shortening advisers give a technical reason to support their posts.
  • rolf_frolf_f Posts: 16,015
    Mr Evil wrote:
    You won't have to shorten the chain, since the smallest combination will remain 34/11 no matter which cassette you switch to. You could shorten it anyway to save a little weight, but I would recommend leaving it, so you can freely swap between cassettes.

    I think the only difference is going to be where the cage is positioned at the extremes. If, with the big cassette, the cage moves from 4 o'clock to 9'o'clock across the range, if you put a smaller big sprocket on and don't shorten the chain ,the cage will be moving eg from 6 o'clock to 9 o'clock which is probably not optimum efficiency. But not anything that anyone who doesn't review bikes for BR would ever notice. Or anyone who doesn't suffer from really bad OCD!
    Faster than a tent.......
  • ai_1ai_1 Posts: 3,060
    I've got a 50/39/30 triple that originally came with an 11-32 cassette (all purpose CX bike rather than roadbike). I've used the same drivetrain with 11-32, 12-27 and 12-23 cassettes without ever changing the chain length - no problems (on second thoughts I'm not certain if it's a medium or long derailleur!)

    Regardless, you shouldn't need to shorten the chain as your intention is to move to a smaller range cassette that's within the range your current setup already accommodates. You may be able to remove links but you won't need to and I wouldn't if you might want to switch cassettes from time to time depending on terrain.
  • zx6manzx6man Posts: 1,092
    The long cage is for taking up the slack on a 52/11 triple so will be fine if its a GS. Although Shimano docs on the canyon links suggest MAX 28T :-)
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