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  1. #1
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    "B" DER adjustment

    I just changed out my cassette(12X25) to a 11X28. My der jocky wheel seems to bounce and bump(against the cog) when in big ring and #11 cog. I had to move the "B" screw a good ways to correct the condition. Can I go too far, and is this the proper adjustment to make. Still new and learning. Thanks for any help.
    ...BUT PAIN DOES NOT MATTER TO A MAN.

  2. #2
    Klaatu barada nikto cascade168's Avatar
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    This is a good reference for your question:

    http://www.sheldonbrown.com/derailer-adjustment.html

    Section 4 addresses "B-index" and "chain length".
    It's possible that you may need to add a link, or two, to your chain now that you have increased the size of the large cog.
    "Work is the curse of the drinking class."
    - Oscar Wilde

  3. #3
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    Thanks Cascade, for the article, and information. Sounds like that's my problem. I'm in the middle of installing my Christmas presents. I have a new chain, and a 24 in chain ring for climbing. I will make that check as I install the chain ring. Thanks again.
    ...BUT PAIN DOES NOT MATTER TO A MAN.

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    Senior Member sydney's Avatar
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    Quote Originally Posted by Road Runner
    I just changed out my cassette(12X25) to a 11X28. My der jocky wheel seems to bounce and bump(against the cog) when in big ring and #11 cog. I had to move the "B" screw a good ways to correct the condition. Can I go too far, and is this the proper adjustment to make. Still new and learning. Thanks for any help.
    Jockey wheel bounce and jump when in the big ring and 11 cog makes no sense, with respect to B tension. Now if you had said 28 cog......you familiar with the repair section at www.paktool.com or a good maintenance book?

  5. #5
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by Road Runner
    I just changed out my cassette(12X25) to a 11X28. My der jocky wheel seems to bounce and bump(against the cog) when in big ring and #11 cog. I had to move the "B" screw a good ways to correct the condition. Can I go too far, and is this the proper adjustment to make. Still new and learning. Thanks for any help.
    Big ring and the 11 cog seems to me like a goofy gear combination to have this problem. I'd expect to find it in either the big/big or little/little combination. I'm wondering if you put on a new chain and didn't size it first. If that's the case, it's likely to be way too long and might cause the problem that you are describing.

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    Klaatu barada nikto cascade168's Avatar
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    Quote Originally Posted by Retro Grouch
    Big ring and the 11 cog seems to me like a goofy gear combination to have this problem. I'd expect to find it in either the big/big or little/little combination. I'm wondering if you put on a new chain and didn't size it first. If that's the case, it's likely to be way too long and might cause the problem that you are describing.

    Good thought. I never even considered that it might be too long. I assumed that when he was going to a bigger cog that, if anything, the problem would be too short.
    "Work is the curse of the drinking class."
    - Oscar Wilde

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