Chinertown
Other Resources => Maintenance, Mechanics, & Tools => Topic started by: cycloholic on October 26, 2025, 11:16:35 AM
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Hello all.
I hope someone out there can help. The front derailleur on my Shimano Di2 105 won’t shift down from the big ring! It’s strange because it’ll still make micro shifts as I run up and down the cassette, but won’t make the shift to the small ring :o
I’ve made sure the battery is fully charged. I’ve disconnected the battery for 60 seconds and reconnected (hoping for some kind of reset), but no luck!
Any help would be appreciated.
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Hello friend,
Maybe this video can help.
https://www.youtube. com/watch?v=Qy6UCIAR7eY
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I would start from the beginning again. The fact that is working tells that there is a problem with the setup and limits. For initial installation look at the page for general 12 speed Di2. For 105 limits specifically:
https://bettershifting.com/installation-guide/set-up-105-and-grx-front-derailleur-limits/
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If you can find someone else with a 12 speed di2 bike, I would recommend taking your fd off the bike and plugging it into their front derailleur di2 cable to see if you can shift it with their shifters. If it works, then you know the derailleur is okay and something else in the system is messed up. If it doesn't work, there's probably some issue with the derailleur itself. Check if it needs a firmware update or something.
you could check if the other bike's derailleur works with your system too.
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I believe 105 has a 1 year warranty so if it's less than a year old you should be able to take it to a shop and they can warranty it if it's broken. Sometimes they don't even check the purchase date so it's still worth a try even if it's out of warranty. You'll have the best chance if you have a shop where you're a regular or know the staff. I managed to get a shifter replaced that was like 5+ years old once.
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Thanks to everyone for your helpful replies and suggestions. It turned out to be a simple fix in the end ;D.
I admitted defeat and popped the bike into my local bike shop. He found that the Di2 synchronised shifting had gone from setting1 to setting2. I probably pressed the button on the rear derailleur by accident whilst cleaning. I have no idea why, but it seems that the shifting pattern in synchro was incompatible with the front derailleur, so the derailleur did'nt know what to do! I didn't know this could happen. Furthermore, whilst fault finding I did look at the synchro on the e-tube app, and thought all looked okay. In the end it was such a quick fix the the bike shop couldn't charge me anything to sort it. Good chap!
Along the way, one useful thing I did lean that may help others. Apparently, to re-set by disconnecting the battery it is not enough to remove the two cables from the battery. if the battery has three ports (like mine), then you also need to remove the blank that is in the un-used port - other wise the re-set does not work.