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  1. #1
    Defender of Freedom...
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    Chain rub with FSA Compact Energy and Dura-ace

    I just coverted my Fondreist to an ISIS FSA Energy Crankset (and FSA P Pro BB) from a non-compact Dura Ace Octalink set up. I have a short cage RD and a DA front derailor and notice significant chain rub in the small chain ring and the 3 smallest cogs. Has anyone else had this problem? Have a fix?

    JR

  2. #2
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    Not uncommon...

    ...as the chain angle in the gear combinations you indicate is responsible. Some will state that you should not be in such combinations due to "cross-chaining." On one of the Shimano instruction sheets, they indicate that you may get rub in the small chain ring and the 2-3 smallest cogs. I get some slight rub on the 3rd smallest cog while in the small chain ring, though I rarely use this combination...usually due to forgetting which gears I am using as I zone out on long country road. You should also not use the big ring and the two largest cogs for the same reason...an added benefit is that you will put less wear-and-tear on your drive train by avoiding these combinations.

  3. #3
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    define chain rub...

    I assume you mean that the chain rubs on the big ring and not the front derailleur? If so, then there's nothing that can be done about that.

    You could check the chainline, but assuming that you used the correct length of BB spindle, it's unlikely to be off by more than 1-2mm. Adding a small BB spacer would at best fix the rub in the third cog.

  4. #4
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    Yes the inside of the large chain ring

    Quote Originally Posted by C-40
    I assume you mean that the chain rubs on the big ring and not the front derailleur? If so, then there's nothing that can be done about that.

    You could check the chainline, but assuming that you used the correct length of BB spindle, it's unlikely to be off by more than 1-2mm. Adding a small BB spacer would at best fix the rub in the third cog.
    Your correct, I'm refering to the large chain ring vs. FD. I'm sure it's a chainline issue (I thought maybe I didn't have the BB all the way in but I reinstalled just to make sure. I'm using the correct BB for the cranks but I swear I didn't have a significant issue with the Shimano set-up. If a spacer improves the shifting on the 3rd cog would this negatively effect another gear combo?

  5. #5
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    yes...

    If the chainline is truly correct, then adding a spaceer might eliminate the 3rd cog noise, but obviously it will create a more extreme chainline in the larger cogs.

    The recommended chainline is 43.5mm to a point out in space, between the two rings. Why in the world, manufacturers contimue to define chainline in this manner is beyond me. How do you measure a point in between the two rings? Since chainring spacing is about 7.5mm c-c, the tip of a tooth on the big ring should measure 47-48mm. Using a scale from the side of the seat tube, subtract half the ST diameter. For example, with a common 32mm ST, the measurement should be 31-32mm.

  6. #6
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    Chainstay length?

    Unless you have VERY short chain stays, it's highly unlikely that you would simultaneously have the correct chain line AND the chain rubbing on the big ring when in the 3rd cog from the bottom. I'd be willing to bet that you'll find the center point between the rings to be to the left of the center of the cassette. A BB spacer will reduce this problem, but you'll likely never get rid of rub with the smallest cog unless you goof up the chain line.

  7. #7
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    try different chainrings?

    I just put on a 36/50 crank, which I use with a 105 front derailleur and a 12-27 cassette.
    I have absolutely no problem, and could probably get away with using all the cogs with both chainrings, though I stick to the top 8/bottom 8.

    My chainstays are 15.75 inches, but I suspect the combination of 34/50 might be the problem. I can tell by eyeballing my setup that if I put on a 34, it would probably rub also, unless I also used a 48 outer ring.

    Why not try a 36? It might solve your problems and give you all the gear you need. I like this ring because I can cruise at 21mph on it with the second smallest cog without shifting. Although I'm tempted to try a 34 for climbing the mountains around here, I would definitely use it with a 48.

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