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  1. #1
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    Di2 6870 FD up-shifting coarsely

    I'm trying to adjust my Shimano Ultegra 67870Di2 Front Derailleur on my Specialized Tarmac SL4. I installed it according to the Dealer's Manual, and I have also used the two Art's Cyclery videos for guidance:
    How to Adjust Shimano Di2 Front Derailleurs
    https://www.youtube.com/watch?v=V-p4qXgbAEc

    The overall problem I'm having is that upshifting from the small ring to the big ring feels coarse. Sometimes I need 2-3 pedal rotations before it engages.

    The video and the documents say that when I use E-Tube or the on-board adjustment mode, the inner plate of the derailleur cage should be 0-.5mm away from the chain, but I can't seem to get it that close, even if I adjust the cage to the extreme limit.

    What am I doing wrong?

  2. #2
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    Neither of those videos include discussion of a key step that IS specified in the Shimano 6870 manual (but the manual is not perfectly clear).

    When you first set up the FD by tightening the mounting bolt, you want the outside of the cage to be both directly over the big chain ring and also parallel with it. That's the final goal. To get there takes two steps:

    1. When you first tighten the FD you want the cage NOT parallel: instead, you want the back of the cage to be slightly inboard. (The videos don't don't make this point clear.) If you start with the FD cage parallel, then in step two you will end up throwing it out of parallel.

    2. Then, when you tighten the support bolt, it will bring the cage BOTH outward overall, and it will square the cage up by swinging the back of the cage out more than the front.

    The Shimano manual tells you to start at .5mm to 1mm off of parallel. And that's about right, on average. But on some bikes you may need to start with the back even more inboard have than this, and that's because the more you tighten the supporting bolt, the further out the back of the cage will swing.

    (On the bike I just set up I needed to start with the back of the cage inward (off of parallel) by about 1.5mm. )

    If you do this first, then when you shift to the small chainring and the biggest cog, it will be easy to adjust the low limit screw such that you make the cage rub. Then just back it off to the .5mm clearance you are looking for. Then set the high limit, and if necessary, the auto-trim micro-adjust, as described in the videos. But my strong guess is that your mistake is with the initial position of the FD and the tightening of the support bolt.

    Make sure when you start that you have backed OUT the support bolt and the high and low limit screws.

  3. #3
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    Di2 front adjustments are complicated. There must be an easy way to do this?

    My Di2 front derailleur cage wasn't quite straight, so I decided to readjust it from scratch.

    It turned out to be a long, complicated process. I set the height above the large chainring to about 1.5 mm. I got the cage lined up straight pretty easily. Then I followed the Di2 Dealer Manual front derailleur adjustment process.

    First, Low adjustment (small chainring) with .5 to 1.0 mm chain clearance on the inside of the cage.
    Now it jams when trying to shift to the big ring.

    The high and low limit screws just don't work like a cable derailleur. Both High and Low move the cage in and out. I expected them to just limit the travel at the edge of the range?

    I had to set the cage to almost touch the outside of the chain to allow it to shift from 34 to 50. I finally got the chainring shift to work, then adjusted the High limit. It still almost touches the outside of the chain when it does the auto trim.

    I wrote a bunch of notes on the dealer manual pages, and I'm still not sure exactly how to get this to work the first time.

    ~~~~~~
    Micro cage adjustment
    This is the "press button on junction box" method.
    The rear has 33 adjustment steps, very easy to use.
    The front only seems to adjust if the chain is in the Big-Big combination!
    The manual says 24 steps on the front.

    Quote Originally Posted by fronesis View Post
    Neither of those videos include discussion of a key step that IS specified in the Shimano 6870 manual (but the manual is not perfectly clear).

    When you first set up the FD by tightening the mounting bolt, you want the outside of the cage to be both directly over the big chain ring and also parallel with it. That's the final goal.

    ...snip...

    If you do this first, then when you shift to the small chainring and the biggest cog, it will be easy to adjust the low limit screw such that you make the cage rub. Then just back it off to the .5mm clearance you are looking for. Then set the high limit, and if necessary, the auto-trim micro-adjust, as described in the videos. But my strong guess is that your mistake is with the initial position of the FD and the tightening of the support bolt.

    Make sure when you start that you have backed OUT the support bolt and the high and low limit screws.
    I must be doing something wrong.

    I thought I tried this, backing out both high and low limits. It was jamming when shifting to the big ring.

    I have a clamp-on derailleur. The screw adjustment that controls the cage angle parallel to the chainring only had maybe 1/4 turn of adjustment. The rest of the screw's range felt loose and didn't change the cage angle?
    Last edited by rm -rf; 04-06-2017 at 02:50 PM.

  4. #4
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    Quote Originally Posted by fronesis View Post

    Make sure when you start that you have backed OUT the support bolt and the high and low limit screws.
    Thanks for the info. This is a useful reply.

    The high and low limit each move the cage inboard counterclockwise and outboard clockwise. When you say back out the high and low limits, do you mean that I want to loosen both screws all the way (both counterclockwise) or that I want to set the derailleur to the maximum span, so the Low limit is counterclockwise as far as it will go, and the High limit is clockwise as far as it will go?

    I also find it very difficult to tell whether the cage is parallel with the chainring just by looking at it from above.

  5. #5
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    Quote Originally Posted by TiCoyote View Post
    I also find it very difficult to tell whether the cage is parallel with the chainring just by looking at it from above.
    Another way is to lay a straight edge across the chainring and move the crank back and forth and look at the gap between the straight edge and the straight edge as it moves across the face of the FDR. Use the limit screw so the FDR really close to the straight edge but not quite touching at the front of the DR, then adjust the jacking bolt till you have the same at the rear.
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  6. #6
    'brifter' is a lame word.
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    Holy crap you guys can make the easiest thing harder than balls. Just so we know, what cadence are you pedaling when trying to shift from small to big? 20? 40? 80? Make sure it's something realistic, not super slow trying to see what happens or not.

    Set the cage up slightly tail-in from parallel, then use the adjustment screw to bring it parallel. It's NOT hard to see, just look from above. Use a wrench or a straight-edge as posted above.
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  7. #7
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    I started two threads about this, so I'm going to paste this reply in both of them. I hope that is okay.

    I replaced the RD hanger with a Wheels Mfg. The new one is a bit softer and easier to align as others mentioned. It turns out both the original and the Wheels were equally out of alignment, so I'm guessing that they were both straight, but the frame is about out of alignment. I understand that his is common for frames, and straightening the hanger is a good practice when building up a frame.

    Next, I removed the FD and repositioned it. This took a few tries. The best method seemed to be moving the low end adjustment outboard until the outside edge of the cage lined up with the big ring. I also needed to angle the tail of the cage in further than I would expect, and then turn the support bolt a little further than the .5mm that the DM suggests. This means that the support bolt is doing more work, and therefore giving the FD more support.

    At this point, everything was shifting accurately, and the skipped shifts and dropped chains had gone away.

    Finally, I replaced the chain and cassette, which I do every spring anyway, and now everything runs great.

    The only remaining issue is that I get some noise when the chain is cross-geared to the big/big combo. I didn't have that issue before I started this process. Perhaps the FD was out of alignment to the extent that it allowed for cross-chaining, but was causing other interference?

  8. #8
    'brifter' is a lame word.
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    Unless your frame has really short stays and/or you're using a compact crank, you should be able to adjust the derailleur so there is no rub when cross-chaining. Remember that the high limit on the front derailleur plays a part in this...you have to have both the low and high set very close, if the high is allowing the derailleur to move too far out when in the big ring the chain can and will rub on the inside of the derailleur cage when you're cross-chained.
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  9. #9
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    I've been playing with it a lot and trying to figure out where the noise is coming from. It's the sort of thing that happens when I'm riding but not when the bike is on the stand.

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