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  1. #1
    Council of the Elders billydonn's Avatar
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    A vs B Chainring?

    Looking to replace the middle chainring on an Ultegra 9-speed tripple of 2004 vintage and I see A and B type rings listed. What's the difference and which do I need? I'm replacing 42t with 39t ring. Thanks...

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  2. #2
    Senior Member mechBgon's Avatar
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    Ideally, you want to use rings that all have the same letter. They're designed to shift harmoniously to/from eachother.

  3. #3
    Insane Bicycle Mechanic Jeff Wills's Avatar
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    Quote Originally Posted by billydonn View Post
    Looking to replace the middle chainring on an Ultegra 9-speed tripple of 2004 vintage and I see A and B type rings listed. What's the difference and which do I need? I'm replacing 42t with 39t ring. Thanks...
    "A" and "B" chainrings are doubles. Sheldon Brown to the rescue:
    http://www.sheldonbrown.com/gloss_aa-l.html#a with this addition: 53's are "B".

    If you want a 39-tooth middle triple, you need this ring:
    http://harriscyclery.net/product/ult...r6656-qc49.htm
    or the equivalent.
    Jeff Wills

    All my bikes.

  4. #4
    Elitist Troglodyte DMF's Avatar
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    As mech says, it's about how they shift together. And there are many more codes than A and B. See the chart in this post for a sample.
    Stupidity got us into this mess - why can't it get us out?

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