Originally Posted by
Ryan_M
Ok I know this is going to be a lot like asking you what my favorite flavour of icecream is but... I'm strongly considering building a road bike and I have to (more or less) blindly pick gearing when ordering the groupset so I'm hopeful some input will give me something to go on. FWIW I'm likely going to go with an Ultegra R8020 groupset.
28/42 bailout gearing you have right now is 18.52 gear inches(on a 40mm tire).
30/36 bailout gearing gives you 22.94 gear inches. That is about equal to 28/34 on your current drivetrain, for reference.
30/36 is about the best you will get for a road bike gearing without getting into expensive or wonky options.
A 46/30 crankset mated to an 11-36 cassette can be handled by an Ultegra GS rear derailleur. The Ultegra RD has an official 39t capacity and the drivetrain I mention would be 41t. 41t total capacity drivetrains are commonly seen on gravel bikes. My gravel bike uses an Ultegra RX RD and 41t total capacity- it works fine.
Any smaller for the crankset though and the FD may not shift as well as its designed to.