Originally Posted by
Badger6
Exactly this. I still use full syncro on my 11-speed Di2 bikes, but I pay close attention to the shift points because it always seems to happen right when I don't want it to happen. It's worse when down shifting than up shifting in my experience...but it is barely noticeable on the 12-speed.
Exactly, because a downshift (on the FD) can happen so quickly that the RD can't keep up.
I suspect the system doesn't generate enough torque to quickly (and simultaneously) shift both the FD and RD...But it sounds like they've worked that out in 12sp, from your post. Good to know.