I'm converting to 10 speed and trying to decide what cassette to use. I'm working with Shimano 105 components and would like to use a compact crankset (50/34). I live in a relatively flat area, with the occasional long, moderate hill.
Warning: here comes the math...
I've done the number crunching on the gears based on my comfortable cadence. I spin between 94 - 112 rpm which are typically my comfortable shift points (i.e. once my cadence drops below 94 I look for the next lowest gear, etc.). With an 11-23 cassette and 50/34 crank, my lowest possible speed at 92 rpm is 10.8 mph. Is that low enough? I'd hate to get towards the end of a century on a long hill and have to mash the pedals at 70 rpm. Due to the cost of 10 speed cassettes, I'd like to get one that works for everything. Should I get a cassette with a 25T gear?
FYI, I use this calculator http://www.panix.com/~jbarrm/cycal/cycal.30f.html plus my own program.