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Weird shifting on Di2 FD shifting
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Running internal battery BTR-2, with 8050 RD, 6870 FD, and 9150 shifters (I know, royal mishmash).

Anyways, I'm adjusting the shifting, and when I attempt to go from 50x11t to 34x11t, the system shifts the rear to the 13t but doesn't shift the front. I have to to downshift the front again to have the chain go from the big chainring to the small chainring.

On my other set-up using DN110 (the newer internal battery), I know i have to select certain combination (usually making the system believe I'm running 53/39t front and 11/25t rear) so that the phenomenon just described doesn't occur. But I was under the impression that this shouldn't even be possible when using older internal batteries, as there isn't even an option to select gear settings. What am I doing wrong?

Thanks in advance
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Re: Weird shifting on Di2 FD shifting [echappist] [ In reply to ]
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I just built up a gravel bike with new GRX DI2 and an old internal battery I have had in a draw for years. When I was setting up my gears with no chain on I couldn't get the derailleur to go to to the 11 and stay in the 13. Having only run older DI2 (which can cross cluster in both directions) I couldn't work it out so went to my local shop just around the corner who changed the front derailleur to the big ring and voila it went into the 11. Seems later gen derailleurs are programmed to stop cross clustering small ring to 11. I can't recall trying to go from the big ring 11 to the small ring 11 and what happens but will definitely go to your 13 and may need two shifts on the lever as it has to do two separate changes?
Last edited by: Shambolic: Oct 15, 20 21:44
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Re: Weird shifting on Di2 FD shifting [echappist] [ In reply to ]
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I accidentally knocked mine into a semi sequential mode while adjusting the other week, but mine decided it was going to find the next available gear at the opposite end ie went from 39/25 or 53/27 or whatever the 2 lowest sprockets are in my bike.
Had to go into the pc software and reprogram it to 0 shifts at either end of the semi sequential mode.
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Re: Weird shifting on Di2 FD shifting [echappist] [ In reply to ]
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I agree that this shouldn't be happening, but it does sort of match the Gear Position Control description on page 127

Specifically:

Quote:
When the chain is in the range [1], shown in the illustration.
Operating the shifting switch does not shift the front derailleur.

Instead, the rear derailleur is shifted down through two gears


Now... you do not need a new battery in order to "use" Gear Position Control, but I always thought you needed both derailleurs to be r8050 or r9150. Apparently that is not the case.
Whether or not GPC is enabled / can be switched off depends on the selected chainring/cassette, as you've already found out ;-).

BetterShifting.com - Di2 help and guides| BetterShifting Instagram | Terry's Instagram
Last edited by: Di2Terry: Oct 15, 20 23:39
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Re: Weird shifting on Di2 FD shifting [Di2Terry] [ In reply to ]
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Thanks for the helpful diagnosis. I guess i can always disable it by connecting it to one of my bikes with DN110. That bike, otoh, uses a 6870 RD.

All so confusing
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Re: Weird shifting on Di2 FD shifting [echappist] [ In reply to ]
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My brain hurts so bad reading this thread. I love my Di2 but have no understanding of how it works, diagnosis, troubleshooting, programming, etc. I'm just happy when I remember to charge the battery.
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Re: Weird shifting on Di2 FD shifting [Di2Terry] [ In reply to ]
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Di2Terry wrote:
I agree that this shouldn't be happening, but it does sort of match the Gear Position Control description on page 127

Specifically:

Quote:
When the chain is in the range [1], shown in the illustration.
Operating the shifting switch does not shift the front derailleur.

Instead, the rear derailleur is shifted down through two gears


Now... you do not need a new battery in order to "use" Gear Position Control, but I always thought you needed both derailleurs to be r8050 or r9150. Apparently that is not the case.
Whether or not GPC is enabled / can be switched off depends on the selected chainring/cassette, as you've already found out ;-).

I finally resolved it. It was indeed a GPC issue, but GPC can only be disabled when using the system with an updated battery (e.g. DN110).

The option to disable it is in the menu for "Shift mode setting", but "Shift mode setting" isn't available when using the older BTR-2 battery. Alas, I had to connect the FD & RD in question to a bike using DN110 to disable GPC. That did the trick.

Thanks again for chiming in.
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Re: Weird shifting on Di2 FD shifting [echappist] [ In reply to ]
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Nice! Thanks for letting us know how to resolve that!

My BT-DN110 bike is currently work-in-progress, so I only had the SM-BTR2 / 6870 to play with :}

BetterShifting.com - Di2 help and guides| BetterShifting Instagram | Terry's Instagram
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