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Discussion Starter · #1 ·
After initial setup, a trip to the LBS, and a lot of fine-tuning on E-tube, I have my Ultegra Di2 6870 almost there. However, I'm still running into a little problem. It feels "sloppy" in the 4th largest cog.

I'm running 36/52 in the front and 11-25 in the back. It's great in every gear except the 19. It feels a little sloppy, as if the derailleur is a bit out of tune, and it's between gears, in the 19 and the big ring. It feels really sloppy in the 19 and the small ring. Occasionally, I get a skipped shift going into that gear.

It's perfect in every other gear combination.

I don't see any visible damage to the cassette. I installed a new derailleur hanger when I built up the frame. The frame is a Specialized Tarmac Pro SL4.

In an online search, I found this thread with essentially the same issue: Di2 11 speed tuning issue? - Australian Cycling Forums - Bicycles Network Australia

Thank you.
 

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Discussion Starter · #3 ·
I do ride in the 19 a good deal. That cassette had about 500 miles on a different bike when I put it on this one. Is it possible that the cog is worn down?
 

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I do ride in the 19 a good deal. That cassette had about 500 miles on a different bike when I put it on this one. Is it possible that the cog is worn down?
Only 500 or so miles? Doubtful wear is the issue. You sure about the mileage? A guy at the shop the other day was amazed his chain was worn out, he said he only had about 800mi on it. Til he checked his computer and discovered it was more like 2200mi.
 

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Wow, I have EXACTLY the same problem. New Ultegra DI2, issues with the 19th cog (4th biggest). Just took it to the LBS for tunning but not result, its the same as before. I'm running a 12-25

Weird!
 

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how is this gadget supposed to work?
You put it on the sprocket. It does 12+ tooth ones. You use the little nub at the end there to apply leverage with the lever to pull the chain tight around the cog. With the chain under tension you check the last special link/roller and see if it drops into place without touching. If it can't be easily dropped into place and lifted without touching, the cog is worn, if it can and there's a gap still, the cog is fine.

 

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Where is the LBS adjusting the rear cassette from, meaning what gear? Shimano tech documents say to do it in the middle of the cassette. I do that on mine, I go one direction counting the "steps" until I hear the chain start rubbing and showing signs of jumping to the next gear, then go the other way and count the steps. From there I split the difference in the steps.

So if I get 9 steps to almost jumping gear and a total of 24 steps to the other side when it shows signs of jumping I move the RD back 11 steps or so and make sure the chain sounds like it is moving smooth with no signs of running.

Adjusting the RD is a sound thing, really easy to tell from sound if you have it adjusted correctly in my eyes.
 

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Discussion Starter · #11 ·
Where is the LBS adjusting the rear cassette from, meaning what gear? Shimano tech documents say to do it in the middle of the cassette. I do that on mine, I go one direction counting the "steps" until I hear the chain start rubbing and showing signs of jumping to the next gear, then go the other way and count the steps. From there I split the difference in the steps.

So if I get 9 steps to almost jumping gear and a total of 24 steps to the other side when it shows signs of jumping I move the RD back 11 steps or so and make sure the chain sounds like it is moving smooth with no signs of running.

Adjusting the RD is a sound thing, really easy to tell from sound if you have it adjusted correctly in my eyes.
That is exactly what the LBS did. I also followed the same instructions.

Interestingly, the correct adjustment seems to be +13, which is near the end of the adjustment range.
 

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If I remember right the Di2 RD has 30 steps of adjustment on the rear. Cassette spacing can change that some as well though.
 

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Where is the LBS adjusting the rear cassette from, meaning what gear? Shimano tech documents say to do it in the middle of the cassette. I do that on mine, I go one direction counting the "steps" until I hear the chain start rubbing and showing signs of jumping to the next gear, then go the other way and count the steps. From there I split the difference in the steps.

So if I get 9 steps to almost jumping gear and a total of 24 steps to the other side when it shows signs of jumping I move the RD back 11 steps or so and make sure the chain sounds like it is moving smooth with no signs of running.

Adjusting the RD is a sound thing, really easy to tell from sound if you have it adjusted correctly in my eyes.
Way too much work.

Go to fifth largest cog.
Adjustment mode.
Move the chain up the cassette with adjustments until it starts to make a little noise.
Move it back down 4 clicks.
Done.
 
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