Nice little program, testtube. I like the rpm vs. speed analysis.

I've got a feature suggestion, though, if you're still taking input.

I often find myself wanting to compare various drive ratios. Say I currently have a 46x16, what would be the next higher/lower possible combination? It's usually not immediately apparent that a 49x17/43x15 would be those combinations (if my calculations are correct.) And if you throw in differing wheel sizes, etc, it gets even more complicated.

I've put together a simple gear ratio table, but would love something more interactive and a little less overwhelming.

Would it be possible to add this "next higher/lower gear" feature with maybe checkboxes to decide whether to include crank lengths & wheel sizes in the combination? It seems like you're already pretty close to this with the "equivalent gear" feature.

Keep up the good work.