Originally Posted by DrIsotope

Let's talk for minute about actually riding a bicycle. For the sake of clarity, we'll (mostly) discard the hyperbolic nonsense associated with big chainrings, i.e what they can do above 35mph. Because I've tested this in practice-- coasting down a hill that is sufficiently steep to go 35mph requires zero watts. Accelerating up to say 37 or 38 miles an hour requires over 200 sustained watts just to combat air resistance. Unless there's a podium at the end of that descent, that's machismo gearing.

Instead I'll focus on "normal" riding. Let's take for example a CDC average male on a bicycle-- 5'9". 198lbs, on a 20lb bike. We will assume he has a reasonable degree of fitness, and can sustain 20mph on a level surface for a decent amount of time. This would be a 52/16 @ 80rpm or 52/18 @ 90rpm. This is roughly a 200 watt effort. The issue arises in that with any typical 11-25 or 11-28 cassette, he's already riding past the halfway point. He has 5 or 6 gears to allow him to go faster, but maybe 3 that allow him to go slower. To pace at say 17.5mph, he would have to be in 52/21, or shift to the small ring.

So outside of downhills, group sprints, or bursts of youthful exuberance, the 11, 12, 13, 14, and possibly 15 tooth cogs are just rotating mass for most of the ride. I'm always amused when people pooh-pooh the notion of 1X, then throw a 52 on the front which renders the bottom quarter of their cassette "downhill only." Let's not forget all of the two-wheeled titans that have to bolt on that 52 because they were spinning out their compacts-- I'm pretty much useless past 110rpm, which would be 41mph with a 52/11. That is a thing I've no desire to do. I don't even want to do it with a 50. I can't do it on the flats, and if the hill is steep enough, gravity can produce a whole lot more force than I can.

I of course speak only from my experience. I ride almost exclusively solo. I'm virtually always either going uphill or downhill. I do not actively seek out hills on most days, but have nevertheless recorded at least 400,000 feet of vertical every year I've ridden. I choose gears to go up the hill, and cash in on that effort by allowing gravity to do most of the work on the way down. I felt perpetually "between gears" with the 52.