Originally posted by sjonz3
I was wondering if anyone has experience using a cyclosport HAC4 computer. How accurate are they in comparison to the other products on the market?
thanks
sean jones
CA, USA
Originally posted by ricstern
Because the sum of all the resistive forces that you must overcome are related to both your size (e.g., frontal area), your bike equipment (aerodynamic drag), the intensity which you're riding and friction and rolling resistances, etc. it's impossible for the HAC4 to estimate these accurately, especially when cycling on level ground. up a steep hill where speed (and thus drag) are very low it becomes somewhat easier to account for these resistive forces. Therefore, the HAC 4 is unlikely to be accurate, especially while cycling on level, rolling roads.
Ric
Originally posted by Feanor
Has anyone made a direct comparison between the power measurement of the HAC4 when compared to the system used by the Polar s720i which is theoretically and reputedly more accurate?
I had both hrm/cyclecomputers at one time, but do not as yet have the s720i power sensor...
Thanks in Advance
Feanor
Originally posted by TimC
Unless you have a power chart that you are comparing yourself against, I would have thought that accuracy is less important than consistent repeatability which allows you to compare rides. If the Hac4 achieves this (and, in my experience, it does), then it can be a useful aid to training. If only the software was better - and if there was some meaningful two-way exchanges between Ciclosport and their customers, this would be an excellent bit of kit. As it is, it's merely good.
Originally posted by TimC
In short, it can't! But on your normal training route, in average UK weather, the figures returned will be similar enough that major differences due to other factors will be noticeable. On my own regular route, my variation in speed and heartrate due to wind are less significant than the variations due to other physical factors, so the power figures given by the Hac4 are pretty valid. Yes, it's a fairly sheltered route, but many are.
The point is that it's not the absolute accuracy of the power figure that's important (unless you want to compare yourself to Lance's power figures - but, note, he uses a Hac4!), but that each time you repeat a given ride at a given speed in similar conditions, the power graph returned is directly comparable to previous episodes. If it is, then changes in power performance can be tracked and used as a training guide.
If you want absolute accuracy, and a system that accounts for changes in wind effect and road conditions, then you are going to have to pay a lot more. That may be good value for you; for me, the Hac4 will do just fine - if only the software was better!!
Originally posted by TimC
There are limitations, obviously, and God knows the Hac4 could be improved, but for the money I don't believe there's anything better. However, the Hac4 does measure temperature and pressure. It's only the effect of wind that is missing from the equation, and only very expensive power-measuring cranks will overcome that limitation. If the Hac4's software was improved, the ability to meaningfully compare rides on the same route would be very much enhanced, even without the wind element.
At the end of the day, it all comes down to money!
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