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  1. #1
    RoadBikeReview Member
    Join Date
    Apr 2006

    12-23 or 12-27 10 spd cassette conversion -- or vice versa?

    looking for an inexpensive way to have two ranges: 12-23 for flatland WI where I live, and a 12-27 for riding in the hills. Looking at the ratios, it seems I could buy the 12-27, buy a separate 18 cog, take out the 27, and have a 12-24. Or I could get the 12-23, take out the 18, add a 27 bailout on the inside and be good to go.

    From: 12/13/14/15/16/17/19/21/24/27 +18, -27
    To: 12/13/14/15/16/17/18/19/21/24
    From: 12/13/14/15/16/1718/19/21/23 +27, -18
    To: 12/13/14/15/16/17/19/21/23/27

    or is it even possible to drop the 12 from the 12-29 and add a 29 to get a 13-29? I'm not too worried about losing the top end speed.

    Anybody have any experience with that, or any reason it wouldn't work easily? I'd look to use Shimano Ultegra.

    Would need to find loose cogs and spacers....

  2. #2
    Low Idiot Tolerance
    Join Date
    Jul 2005
    I don't see why it wouldn't work. But...

    That's a lot of farting about, it would be simpler to buy a second cassette. Yes, I realise you said "inexpensive" but you're trading off cost for convenience.

    If it was me, I'd run a 12-27 and when I was on the flat, I'd ignore the 27. They're gear ratios, you only use one at a time, so don't use the one you don't need to use. Simple.

    Is having that 18 wedged in there between the 17 and the 19 really going to enhance the cycling experience that much to justify getting grubby fingers every time you want to ride a different area?


  3. #3
    RoadBikeReview Member
    Reputation: Kuma601's Avatar
    Join Date
    Jan 2004
    Would a 12-25 and a different small chainring get what you want?

  4. #4
    RoadBikeReview Member
    Reputation: tuscanybill's Avatar
    Join Date
    Nov 2005
    There is a way to avoid buying a whole cassette

    You can buy the riveted large gears seperate from Shimano, depending on your shop this may or maynot be cheaper

    Example to take a 12-23 to a 12-27

    you need two items

    Y-1ZD 98120 (this is the 21/24/27 togather)

    and Y-1ZD 1900E (this is the 19 to replace the 18 on tthe 12-23)

    This info is from this Shimano site (Please check the numbers yourself to confirm)

    Click on the componet (cassette sprocket) and then select your cassette and you will see the compleate parts list

    If you have a good shop they can order these parts for you, I would check the price as sometimes you can get the cassette for only a little more. You can then "rotate" them to cut down on wear.

    Hope this helps -- Bill

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