As part of my never-ending quest to overthink everything, I took a quick look at my shifting pattern. This has probably been done before, but I haven't seen it. Goal was to shift from the smallest gear ratio to largest with the most even steps and in a way that was simple and avoided high-loss combinations.
I have 30/39/50 teeth on the front, 11/13/15/17/20/23/26/30/34 teeth on the back.
I measured the approximate lateral separation of the rings, in mm. Higher separations were avoided. Also gave a bit more preference toward higher tooth count combinations, since I believe those result in less friction loss.
Tried to avoid small/no changes in gear ratio (delta ratio), as well as large ones.
Weighted all of these things to assign an overall value to the combination. Value is from 0-10, with higher being better. It really doesn't mean anything by itself, but might be a sign to look closer at a particular combination.
Here is what I came up with. Nothing terribly surprising here, but it should optimize everything a bit and isn't hard to remember. Will probably paint a couple small dots on my shifting indicators to help.
One interesting thing is that there are only 13 combinations here. The eliminated ones really wouldn't add much functionality. This supports my plan to eventually replace that 3 ring front.
Got a couple questions too.
Anyone have a better way to measure lateral separation of the gears? I just used a straightedge on the largest front ring and measured from there. Fairly accurate, but could be better.
Also, why don't we see something like 4 front and 4 rear gears? It shouldn't be too hard to write up something that, when given min/max ratio, min/max gear size, and number of gears of front/back would assess all possible tooth counts to find the one with the most even spacing. I suppose it would make things a bit less intuitive - needing to change both the front and back gear for more of the jumps. Would be interesting to see that combined with computerized gear selection. That might be a project for another month though.