Originally Posted by 2Rodies
Which is why I went with the HAC4. Full bike computer w/HR/Watts and downloadable for under 300 bucks. It does everything as well as the Polar unit does but it's not as accurate. Last month I did side by side test with one of my teamates. He has the Polar S720 with watts. We are about the same weight, bike and rider and about the same age 43/45. We did a climb of just under 2 miles and maintained the same speed and gear while riding next to eachother. At the top we checked our measurments. His max wattage was 580 watts with an average of 420. Mine was quite a bit less 420/270 respectively. I can only guess that the Polar units way of calculating watts (chain tension) is more accurate than the HAC 4 which uses gradient/speed/virtual wind resistance.
the problem with the HAC4 is when you are riding into the wind, which I seem to do an unreasonable amount of the time, at least in my opinion. I was riding with this guy (same one as in the first reply) and he's got a HAC4...we were hammering into this really awful headwind at around 17 mph or so, and it was really hard, my HR was around 80%...anyway...I remembered his HAC4 and I asked, "so how much power you makin? 400watts or so?" he goes, "well...its actually like 150..." and that totally demoralized me...