Originally Posted by
redlude97
But you said you were going to a subcompact, but did not include a compact. That was the point. What you are missing is that the difference between a 50 and a 52 is 5GI, whereas the difference between a 46 and 50 is 10GI. In your "comfortable" descending cadence of 80-100rpm the difference between 52x11 and 50x11 is ~1mph. This does not equate to "opening up the range of gearing available". Like I said, why are you insistent on the need to eek out an extra 1mph on the top end where you spend less of your time? This would be a different discussion if you were wanting to run the midcompact with an 11-25 or comparable gearing where there aren't big jumps in the cassette to accommodate a 32T
So you assumed I was moving from a compact. Agreed 50-52 ain't that much there.
What's so big about the gear jumps in the comparison chart above? The gear steps from 18-28mph is accounted for, the exception being 23mph @13% but that can be crosschained (36x11) at worst if the gap proves troublesome and the bike is set up to do so.
The difference between a 52 and 46 is almost 15 gear inches with my current setup. That puts the top two cogs within a higher speed bracket at a given rpm where I can gain an additional 3mph. but, it isn't about the academic finite here. It's about placing gears at a point where I can much more effectively maintain speed or accelerate via torque instead of spinning like a hamster. Descending at speed places more emphasis on maintaining momentum against drag versus being on the flats. I spin out 46x11 regularly where I live.
I see no disadvantage going to a 52/36 and 11-32. That maintains my lowest gear requirement which is for anything sustained at 13% and up,