Oh yeah, aging sucks, doesn't it? The trick is to age without getting old. Part of that is feeling free to change things as you go. "Old" = being stuck. I work out in the gym more now and spin smaller gears at higher RPM. My road bike is a 9-speed with 53-39-26 and 11-30 in the back. Our tandem is 10 speed, same in the front, 11-40 in the back. If you go to a 39 middle ring, it'll be 10-speed but work fine with the 9-speed brifter and FD. However the 39T middle demands the 53T outer ring that's normally used on a 53-39 double. Makes sense.
On the 26-40 rig, I couldn't set the chain for big-big. I made it 2 links shorter and am just careful. My wife's single has a MTB triple crankset. That works fine too, and eliminates the big-big issue.
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