Joined: Jul 2007
Posts: 8,586
Likes: 3,518
From: South shore, L.I., NY
Bikes: Trek Emonda SL7, Cannondale Topstone, Miyata City Liner, Specialized Chisel, Specialized Epic Evo
Curious what 1X Di2 system you are putting together ?. Is this a drop bar gravel build with a road group ?, or flat bar mt. build ?
If drop bar, the GS Ultegra rear derailer only handles up to a 34 tooth cog, you might stretch to a 36. That kind of defeats the while 1X concept of letting the 46-50 cassette give you your low range.
And why go 1X ?, one of the many advantages of Di2 is the front shifting is exceptional.