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From my understanding, doing this will damage both the front and the rear derailleurs' servos and / or gears:

https://youtube.com/clip/UgkxQsBoKA0qG0Mfgwo435Xr6aLnD8TOTrRB

However, this is fine since it's essentially tightening the b-screw:

https://youtube.com/clip/UgkxnsLa4R3NFZhp7k-Yf_8b_JS58Z4TRGOY

And this is fine too:

https://youtube.com/clip/UgkxIsI9aSUdI0_NkI4y_TfcWwjxMm4lnJ8P

Is my understanding correct? If possible, please provide references to Shimano documentation.

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  • I think I can see a worm gear in this Di2 front derailleur teardown, which would mean it can't be backdriven: bettershifting.com/taking-a-di2-front-derailleur-apart Worm gears provide a lot of gear reduction and allow the servo to hold position without any power (i.e. even if the battery runs out).
    – Michael
    Commented Jun 11 at 8:58

1 Answer 1

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I tried pushing my R8150 Di2 derailleurs with quite some force and neither of them move. The servo's gearbox doesn't seem to be backdriveable.

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