More on gearing

Google found me this page on cadence and gearing. I know a very very long time ago I made a gearing chart for my old bike, internalized a couple of details ("one front shift is worth about 1.5 rear shifts") and lost the chart. Since everything is on the Internet now, you can find, say, the gear sizes for SRAM cassettes without getting down and counting, and find out which one your bike has by looking at its Web page. Comparing my bike to the locally popular Bianche Volpe, in gear inches:

Specialized Sequoia Elite					Bianche Volpe
	30	39	50			28	38	48
26	30.4	39.5	50.6		32	23.0	31.3	39.5
23	34.3	44.6	57.2		28	26.3	35.7	45.1
21	37.6	48.9	62.7		24	30.7	41.7	60.2
19	41.6	54.0	69.3		21	35.1	47.6	60.2
17	46.4	60.4	77.4		18	40.9	55.6	70.2
15	52.6	68.4	87.7		16	46.1	62.5	79.0
14	56.4	73.3	94.0		14	52.6	71.4	90.2
13	60.7	79.0	101.2		12	61.4	83.3	105.3
12	65.8	85.5	109.7		11	67.0	90.9	114.8

(The numbers are gear ratio times wheel diameter in inches; I'm assuming both bikes have the same wheel circumfrence of exactly 210 cm and working from there.)

The differences appear to be all about the rear cassette. "11-32T" doesn't sound that different from "12-26T", but that difference means the Volpe has a 23% lower lowest gear (even a little lower for having an 8% smaller chainring) and an 8% higher highest gear (again slightly less for the smaller chainring). The flip side of this is larger steps: the Sequoia has a geometric mean of 10% between gear steps, but the Volpe 14%. So I have better gear resolution, about the same top speed, but less climbing power. My understanding is that replacing the cassette is a reasonably routine bike-shop repair; it might be something to keep in mind if I find hills routinely defeating me.