Originally Posted by
dr_lha
The CX70 has a different shaped cage that is better optimized for a smaller large ring (46T), but otherwise is identical to the FD-4600 in function (assuming you have the bottom pull version). However that shouldn't affect the function of the FD when you're in the small ring at all, so I would be willing to bet that a better adjustment of the derailleur is needed. I assume you had to move it up the frame when you put on a big ring? Make sure the FD cage is correctly aligned.
This. I use a Di2 9070 FD with a 46/30 crankset (square-taper LOL) with an 11-32 and it doesn't make noise. The Di2 roadie FDs were never made with anything lower than 50/34 in mind.
OP, this sounds exactly like an alignment and placing issue of the FD. SO long as you don't have a riveted/etc. FD braze, you should be able to get the FD to the place it needs to be to do what it needs to without noise.