Average mph? I've tried all kinds of ways to figure it & finally decided that 1) if I know the distance relatively accurately and 2) knowing there are always many reasons why, on any given day, I'll slow down, stop (for a light, the train, etc) then 3) I'll just time from when I roll out my driveway until I roll back in. That's accurate enough for me considering, as you stated, conditions change from ride to ride even on the same course. The HRM provides more useful info about my conditioning challenges than any 'average mph' statistics, at least for me.
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centexwoody
They're beautiful handsome machines that translate energy into joy.