Best cog to convert Shimano Megarange 11-34 to 11-24,26,28?

Discussion in 'Cycling Equipment' started by god, Feb 9, 2004.

  1. god

    god New Member

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    Bike Kats,
    Perhaps you can help me.

    Summary Question:
    I want to replace the 34 tooth cog on my Shimano megarange 11-34 freewheel with a smaller cog, like 26, or 28.
    What's the best type of cog to do this with?

    I haven't looked into the details of this other than studying Sheldon Brown's article on the this 11-34 freewheel which shows how to access the 34 tooth cog.

    Desired Solutions:
    1. Ideally there exists a (insert manufactures name here [i.e., Suntour]) cog that fits perfectly.
    2. Less ideally, some minor Dremel tool machining of a cog that almost fits would make it fit nearly perfectly.
    3. Even less ideal, major machining, cutting, welding, would be required.

    I believe the correct answer is 2.

    More detailed verion of the question:
    Answering the question "why do you want to do this?"
    I want a super wide range gearing on my Santana Rio Tandem. Say 15-130 inches.
    The rear dropout spacing is 140mm. (Its an old tandem.)
    The rear hub supports a freewheel.
    I don't want to put a dished wheel on my tandem (too weak in my opinion), that means I want to stick with 7 speeds.
    I don't want to go to a freehub at this time. When the rim wears out from braking I'll consider a whole new rear wheel with what is available at that time.
    Current gearing is 24-44-54 with Megarange 11-34 on 26 inch wheels.
    Major Problem: There is too big a jump in this gearing because it lacks gears in the 33-47 inch range. This around 8-10mph and is a noticeable gap at a critial speed.
    I'm working on adding 4 chainrings in front to make a quad 16-28-44-54. This will smooth out the gearing, and eliminate the need for the 34, which can then be replaced with a 28 still producing a glacial 14.86 inch gear.
    In theory, with the quad, an even tighter 11-12-13-15-18-21-24 cluster could be built having a 17-127 inch range with no major jumps.

    The Paragraphs detailing how to perform quad gearing are omitted at this time (since I haven written them.)

    Long term solution would of course be a new Santana Tandem.

    Thank you
    Paul Stankiewicz
     
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  2. boudreaux

    boudreaux New Member

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    Use the 28 off a shimano 7 speed 14x28 freewheel. Sheldon may have loose cogs. A 26 off a Sram 13x26 is also a possbility.
     
  3. god

    god New Member

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    boudreaux,
    Thanks I'll give a 7 speed cog a try.
    Do you know if its a perfect fit or will require some machining?

    I was thinking last night that my posting had a lot of information in it (too much) but I didn't really describe exactly what I was asking.

    The real question is:
    Is the 34 tooth cog on the Shimano 11-34 Megarange freewheel interchangeable with any other cog specifically with regard to the spline pattern that allow it to slide onto the BACK of the carrier?

    I know that the 11-34 mega is a different design than the 14-34 mega.
    See this posting for details for replacing the 34 on the 14-34 mega:
    http://www.cyclingforums.com/showthread.php?threadid=4441&highlight=megas

    In this posting Sheldon mentions nothing will work to replace the 34 cog on the 11-34, I quote:
    "the 11-34 is a radically redesigned unit, and nothing on it is interchangeable with any earlier freewheel. The splines for the 34 are quite a lot larger than all other models."
    So I guess I should be asking "what's the closest cog that will almost fit?"
    I'm thinking someone must have performed a delicate transplant like this before.

    Thanks again.
    Paul
     
  4. boudreaux

    boudreaux New Member

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    Sheldon is usually right,and I was not aware of the totally different design of the 11x34 megarange. Just proves again you can learn something new almost every day.
     
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