Originally Posted by
ThermionicScott
Let's say a person has a 50/34 crankset and an 11-28 cassette. Even though they *could* use the 34/13 combination, there is no advantage over the 50/19. The 50/19 runs smoother, wears the chain at a slower rate, and still has plenty of runway in both directions. So personal fitness and terrain don't enter into it.
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I agree that the 50/19 would be better if that suits a consistent cruise speed for wherever you are. In a perfect world we can always be riding in the middle of the cassette, and generally that's what we aim for for either of the front chainrings.
But if the 34/13 is where you end up, perhaps during some flat sections on some rolling climbs, it can have utility if it gets you back to your climbing gears without necessitating front der changes. In other words, the 13 is part of the runway you refer to, but for the small chainring.