cassette mix & match question

Discussion in 'Cycling Equipment' started by blkhotrod, Sep 21, 2009.

  1. blkhotrod

    blkhotrod New Member

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    i have 2 dura ace 7800 cassettes.
    #1 corn cob 21-11 in excellent shape
    #2 25-11 older cassette with lower gears pretty bad.

    i have a race which has 6000' climbing and need a good cassette.....so can i

    take the 25-23-21-19 single piece from the older cassette and put it behind the bottom 6 gears from the good 21-11 cassette= 25-23-21-19-16-15-14-13-12-11

    thanks
     
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  2. alfeng

    alfeng Well-Known Member

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    Sure. If the larger cogs are in reasonably good condition, then "Why not?"

    BUT, try it before the race to ensure that there aren't any conflicts with the chain.
     
  3. maander`

    maander` Member

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    The 16 - 19 is a bit of a jump isn't it?
     
  4. alienator

    alienator Well-Known Member

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    16-19 is a real big jump, and it's in what is a sweet spot on a cassette for a lot of people. It's likely because of the 11 tooth cog on the one cassette. 11 teeth is hard to justify sometimes. On a descente in 50/11 at 100 rpm, that'll give you 35 mph. Of course with a 53 it's faster, at 37 mph. A lot of people would argue that an 11t doesn't even make much sense on a descent, that a 12t wouldn't cost you that much. Plus, with a 12t, you can another cog in that 16-19t range. FWIW, a 53/12 at 100 rpm gives you a speed of almost 35 mph. You're talking about gaining 2 mph with an 11t high gear instead of a 12t (This was assuming a tire circumference of 2100 mm......I thought I'd be generous.).
     
  5. swampy1970

    swampy1970 Well-Known Member

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    Did Shimano ever officially produce a 11-25 Dura Ace 7800 cassette? I know they now make one for the 7900 group.

    On the 12-25 the 17-19 and 21-23-25 were combined on the alloy carrier.
    On the 11-21 the 17-18 and 19-21 were combined.
    So unless you get creative with a dremel or a drill you're stuck with the 5 largest sprockets...

    If you're mixing a 11-21 and a 12-25 then you could get:

    11,12,13,14,15,17,19,21,23,25
     
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