Joined: Jun 2013
Posts: 4,094
Likes: 2
From: Bozeman
Bikes: 199? Landshark Roadshark, 198? Mondonico Diamond, 1987 Panasonic DX-5000, 1987 Bianchi Limited, Univega... Chrome..., 1989 Schwinn Woodlands, Motobecane USA Record, Raleigh Tokul 2
Sorry, going to a 1x when you have bad knees and freely admit that you need lots of gears sounds like a stupid idea.
1x drivetrains are really for strong riders who can power up hills, or for somebody who never wants to go faster than 20 MPH.
You've convinced yourself that a 1x is a good idea. Take a step back and look at it again.
The problem, as someone mentioned above, with the max tooth size limit on a derailleur has nothing to do with the front chainrings. Derailleurs have a hard maximum for the largest tooth cog they can accommodate. Anything above that and the derailleur itself will plow right into the large cog when you're shifting.