"Peter Cole" wrote:

"VBadJuJu" none@ wrote

Highly accurate too at least as to speed (and therefore distance, avg
speed etc). Recently there was one of those automated radar speed
things down the street off and on for about 9 weeks. Coming down the
hill on my way out to ride I could verify the read out vs the radar
thingie.

Bike "computers" are simple wheel revolution counters, they're all as accurate
as the tire size input.

No, not "all" of them, which is why I mentioned the accuracy.

Counting revs alone will only get you the distance covered. You need
the capability to track the time between revs with a degree of
accuracy and granularity.

I've had more than one very cheapie that had serious trouble tracking
that time and therefore the speed readout was inconsistant. On one I
suspect the average speed was ok, but the sporadic flashes of 141 MPH
left me with little overall confidence. Another only seemed to be
accurate as to time factors when the battery was brand new: otherwise
after a 2++ hour excursion, the 'ride time' would report as 38 mins.



FWIW, 13 - 15 miles works out to about 1000 calories at 10.5 - 11.5
MPH average for me.

That sounds off by a factor of 4 or so, it's way too high unless that is up a
very steep hill. You can't accurately measure calories without measuring
watts, and that's a difficult thing to do, the equipment is available to do
that (e.g. Powertap), but it's expensive.



Apparently it is pretty accurate, more so than you imagine.

It is quite in line with several online fitness calculator/estimates:
1000 vs 997 vs 1060 vs 1297 vs 937 vs 1301. (I forget the exact
weight factor I have input on the 'puter, so the max variance of 300
doesnt bother me; the average variance is only 144.)

One key element would be the type of bike/tire. Obviously fewer
calories are burned on a road bike at 11 MPH than a mountain bike.
Using the same factors, the online calculators result in only 600 -
900 calories for generic bicycling - still about double your estimate.

Given that the calculator is so in keeping with the other estiamtions,
I suspect the computer infers the bike/tire type from the wheel factor
input.


YMMV