Upgraded to DA 10 as I wore out most of my 9 speed stuff. Was using an 11-25 with my 650 wheels. I have made a new 11-25 DA 10 speed from a 12-25 with a new lockring and 11 t cog. I have the 14 in there which I like but wondered if for a hilly course say like the upcoming Auburn Half Ironman if it wouldn’t be better to have the 16 instead of the 14. Options below.
It’s impossible to say without knowing what size your chainrings are, but if you’ve got a 53x39, then on 650c the 14 gives you:
67.7 gear inches in the small ring
92.0 gear inches in the big ring
The 67.7 is virtually identical to the 53x19, a perfectly rideable combo, so it doesn’t factor in. The 92 however is actually a rather useful and non-redundant gear, close to the “all american” track gear of 90 inches (50x15 on 700c) and by that yardstick a nice gear for a brisk cadence on flat ground, but certainly not a climbing gear for most mortals.
The 16 gives you:
59.3 on the small ring
80.5 on the big ring
The 80.5 is pretty close to the 79.0 inches of the 39x12, so whether that’s redundant depends on whether you think going from the small ring to the second smallest cog is too crossed-up on a 10 speed drivetrain - hopefully it’s not.
The 59.3 is pretty close to the 53x21 (61.4), which is reasonably un-crossed-up.
Based on all that, the 14 appears to offer 1 useful gear and the 16 offers none.
If the assumption about the chainrings is wrong, this is all out the window.
If you want a sweet gear to spin on the flats or push up gentle grades, can I hear an amen for 42x16 on 700c? Which is unfortunately right in between a 13 and a 14 with a 39 tooth chainring on 650c - the 53x19 is pretty close but somehow it just feels better in the small ring.
Back to your original concern about hilly courses - I don’t think the 16 or the 14 have much to do with big hills, so you aren’t going to go too far wrong with either from that angle.
Do you normall race in a 14t on the flat sections? Or are you up in the 16t? That is what I would comtemplate. There are a few flat sections in the AIT course but not many.
If it was me, I would keep the 16 and keep the 14t. That is me though, I am basing it on what gears I like to ride in. You are lucky, you have an 11t to turn over in the race. I am jealous.