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  1. #26
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    Quote Originally Posted by Lombard View Post
    Agree here too. There is no way to prevent this rubbing in the small/small combo. Believe me, I tried by adjusting the FD cable and ended up with chain drop issues. So you have only two choices. You can either not use the small/small combo OR you can just live with the noise and the eventual grooving of your FD. Period.
    Rubbing is on the chain ring, not the FD cage. The grooves will be on the inside of the big ring.

  2. #27
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    Sorry to dig up this old thread, but not much out there in regards to C2 crank compatibility issues.

    I understand the OP's frustration, I have an Aluminum 68mm English Threaded BB with eTAP Gxp that is plagued by the same exact issue.

    However, I am able to cross-chain all day long with my Di2 bike without the chain rubbing on the inside of the big ring (using both, 6800 & SiSl w/Opi Cranksets).

    I also went through a lengthy exercise, in which I transferred the Etap groupset onto my Di2 Bike (BB30 S-Works Tarmac w/Cannondale SiSl OPI Crankset), obviously I could not use the Red GXP Crankset. All worked fine in any combination without the chain rubbing on the inside of the large chainring.

    SRAM mentions chainstay length as a likely culprit, but I also don't have any issues with cross-chaining on a 2 sizes smaller frame (shorter chainstays) using 6800 cranks. That bike is also a 68mm threaded BB (so apples-to-apples...sort of).

    Yes, we all know that cross chaining is "bad" and wears components quicker, but to me it seems that in this case it is the Sram Red Crankset, more specifically the chunky machining (on inside of the large chainring), along with tight spacing between rings.

    Like the OP, I too thought about running 1~2mm spacers between the the "Large Chainring and spider" to push it out just a tad and give the small ring enough clearance to accommodate the chain in those extremes. Not sure if it's doable, or how drastically that would affect the chainline while in the large ring, but might work.

    I do understand that the 11sp chain is narrower, and increasing the distance between the chainrings can potentially lead to the chain getting jammed between rings during shifts, but I doubt that the addition of a 1mm spacer would lead to this.

    Lastly, I have not measured the clearance between the chainrings on the cranksets which work flawlessly with Di2 and eTap in all gear combination, but it seems clear that it must be different...and BTW I am running Dura-Ace CN-HG901 chains on all my drivetrains.

  3. #28
    'brifter' is a lame word.
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    Quote Originally Posted by mieszko_I View Post
    Sorry to dig up this old thread, but not much out there in regards to C2 crank compatibility issues.

    I understand the OP's frustration, I have an Aluminum 68mm English Threaded BB with eTAP Gxp that is plagued by the same exact issue.

    However, I am able to cross-chain all day long with my Di2 bike without the chain rubbing on the inside of the big ring (using both, 6800 & SiSl w/Opi Cranksets).

    I also went through a lengthy exercise, in which I transferred the Etap groupset onto my Di2 Bike (BB30 S-Works Tarmac w/Cannondale SiSl OPI Crankset), obviously I could not use the Red GXP Crankset. All worked fine in any combination without the chain rubbing on the inside of the large chainring.

    SRAM mentions chainstay length as a likely culprit, but I also don't have any issues with cross-chaining on a 2 sizes smaller frame (shorter chainstays) using 6800 cranks. That bike is also a 68mm threaded BB (so apples-to-apples...sort of).

    Yes, we all know that cross chaining is "bad" and wears components quicker, but to me it seems that in this case it is the Sram Red Crankset, more specifically the chunky machining (on inside of the large chainring), along with tight spacing between rings.

    Like the OP, I too thought about running 1~2mm spacers between the the "Large Chainring and spider" to push it out just a tad and give the small ring enough clearance to accommodate the chain in those extremes. Not sure if it's doable, or how drastically that would affect the chainline while in the large ring, but might work.

    I do understand that the 11sp chain is narrower, and increasing the distance between the chainrings can potentially lead to the chain getting jammed between rings during shifts, but I doubt that the addition of a 1mm spacer would lead to this.

    Lastly, I have not measured the clearance between the chainrings on the cranksets which work flawlessly with Di2 and eTap in all gear combination, but it seems clear that it must be different...and BTW I am running Dura-Ace CN-HG901 chains on all my drivetrains.
    It's quite simple. Don't cross chain small/small. Only use what works, there is no sense in using small/small. Do NOT put any spacers under your big ring. There are more engineers designing these systems than you can shake a stick at and they all have the same answer to this issue.
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  4. #29
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    I do understand that the 11sp chain is narrower, and increasing the distance between the chainrings can potentially lead to the chain getting jammed between rings during shifts, but I doubt that the addition of a 1mm spacer would lead to this.
    It would most certainly lead to this. The indexing of the front shifter is designed to work with the spacing of the chainrings WITHOUT modification. If you move the large chainring outbound 1 mm (which might as well be a mile in terms of front derailleur adjustment), then the index cable tension to reach that chainring would be so high, you would never be able to shift back down to the small ring. With the additon of the extra 1mm between rings, when you did shift back down, the chain would not go all the way to the small ring and most likely jam in the space between.

    I cannot for the life of me understand why people feel the need to ride in the small/small, and would consider modifying precision shifting systems just to make that possible.

  5. #30
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    Quote Originally Posted by 202cycle View Post
    I cannot for the life of me understand why people feel the need to ride in the small/small, and would consider modifying precision shifting systems just to make that possible.
    This. Small/small and large/large were not designed to be ridden. There is absolutely no reason to use either of these besides laziness.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

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  6. #31
    'brifter' is a lame word.
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    Quote Originally Posted by Lombard View Post
    This. Small/small and large/large were not designed to be ridden. There is absolutely no reason to use either of these besides laziness.
    Not so fast. Big/big is something that should work and needs to work. Small/small is just dumb.
    I work for some bike racers
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  7. #32
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    Quote Originally Posted by cxwrench View Post
    Not so fast. Big/big is something that should work and needs to work. Small/small is just dumb.
    Why would you ever need big/big?
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  8. #33
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    Quote Originally Posted by Lombard View Post
    Why would you ever need big/big?
    Because you don't want to risk a front shift. Racers do it ALL the time. Or, look at it this way. Out of the box, the new Di2 won't allow shifts to small/small or even the small/12. But it will definitely allow you to go big/big. To a LOT of people big/big makes sense every now and then. Trust me on this one.
    I work for some bike racers
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  9. #34
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    Quote Originally Posted by cxwrench View Post
    Because you don't want to risk a front shift. Racers do it ALL the time. Or, look at it this way. Out of the box, the new Di2 won't allow shifts to small/small or even the small/12. But it will definitely allow you to go big/big. To a LOT of people big/big makes sense every now and then. Trust me on this one.
    Well OK, I guess if you are a racer, it is prudent to avoid front shifts. A chain drop can lose a race. And I presume many racers are strong enough that they seldom use small ring.

    For myself, I generally shift the front when I'm in one of the middle cogs in back. If I'm in the small ring and getting near the small in back and want more speed, I shift to the large ring. If I'm in the large ring and I see a hill ahead, I immediately go to the small ring. So neither extreme is necessary for me.
    "With bicycles in particular, you need to separate between what's merely true and what's important."-- DCGriz, RBR.

    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein



  10. #35
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    Quote Originally Posted by Lombard View Post
    This. Small/small and large/large were not designed to be ridden. There is absolutely no reason to use either of these besides laziness.
    I don't see an issue with large\large, but by the time small\small is arrived at the big ring should be engaged. Shifting into bigger gears is probably going to be more long term than smaller gears.
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