Originally Posted by
kenrudman
Or you could buy a unit that uses a GPS, like the Garmin 500, which has a second bike setting, will work without a sensor, although I think you need a sensor on the second bike to determine wheel size automatically...
I second this however, if you use a gps like said 500 (which I'm now using) then wheel size doesn't matter if you aren't using the cadence/speed sensor. It also calculate the speed from gps.