ibike pro power meter?: Triathlon Forum: Slowtwitch Forums

That is very interesting.

If it proves to be accurate then at $350 it will mean "power to the masses" which is a good thing. Even if the wattage indicators are not that accurate, the other functions make it very appealing as a plain bicycle computer.

However, since it is using an airspeed indicator, I would have my doubts about how close it comes to your real watts. Of most interest was this question:

3. What if I change riding position, how does that impact the iBike wattage reading?[/url]

Most riders stay in the same position about 90% of the time or more, so the percentage of the total ride where there is a wattage difference won't be great. The iBike Pro assumes that the athlete remains in the same riding position, so changes in riding position will not be reflected by changes in the iBike's wattage readings.

However, remember that the overall wattage "error" caused by ride position is moderated by other wattage components. For example, let's suppose that, at a particular point of the ride, the iBike is reporting 200W. Remember that the iBike "knows" where the watts are going. For example purposes, our rider is on a level road with no acceleration. The wattage breakdown is: 50W due to rolling resistance and friction, 150W due to aerodynamic resistance.

Let's suppose that the rider is out of his normal riding position on the hoods and that this is causing a 10% underreporting of aero watts. The iBike Pro would be reporting 200W instead of 215W. The total wattage variance at this particular instant of the ride would be 215W/200W = 7.5%, not 10%, and only for that portion of the ride. If the iBike is off by 7.5% for 10% of the time due to riding in the drops, the net error over the whole ride is only 0.75%. That's less than 1% and is well within the accuracy range of competitive products.

Apparently if you change positions, the accuracy of the reading is suspect. For a race this isn't a big deal, since I assume most people stay on the aerobars, but on a long ride or in places where you are climbing a lot, it would not be very accurate.

Plus, what does it tell you if you are drafting? Is this a totally ride by yourself tool?

Chad

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