On my bikes without the cadence thingy (which indeed, has a different wire and goes with speedometers that hook up to the rear wheel; I got it so I could see how "fast" I was going on the trainer, and that's *really* a meaningless number except compared with itself!), I don't try to do fifteen seconds and all that (though it would be good anti-Alzheimer's training, I'm sure)... I do figure that one full cycle (left-right) in one second is 60 rpm, and left-right-lefgt is 90 rpm, and try to get a little closer to 90 than 60. If I am really getting carried away I see how quickly I can "lap" myself, and then try to figure out what ratio to use to calculate rpms from that... but that's getting dangerous...