doulos said:
How did Polar and iBike do on the road? I've got a Cycleops trainer with power for the indoors. Thanks Tim
The SRM was give the baseline value as it was the unit in which they were able to calibrate for accuracy.
Test 1 - Bunch ride
Average power over the ride:
Power tap - Same as SRM
iBike - over estimate by 7%. Ergomo - Polar - had some transmission problems and a average over the ride was not possible.
Ergomo- over estimate by 11%
All units responded well in measuring uphill efforts with all unit showing similar readings. The iBike was found to be inaccurate during drafting and downhill and not particularly reliable in this type of application. The Polar was a little slow in keeping up with measuring surges, which resulted in showing more time in lower powerbands. Ergomo tended to show more time in the higher bands.
Test 2 - Four Time Trial Efforts
These efforts were measures of trying to maintain a prescribed target power and cadence for periods between 3:30-4:30min
On average
Powertap - consistently similar to SRM\
Ergomo - consistently 14-16% over estimated
Polar - consistently 23-31% underestimated.
iBike - varied from +3% to -7%
it was thought that as the Polar and Ergomo were consistent in their measurement that this would still provide a basis of comparison for training purposes.
Test 3 - Black Mt Repeats (2.4km w/ave 8.9%)
Two riders on separate days put each unit to the test with two climbs each
Powertap - similar to SRM
Ergomo - Rider 1 - over estimate 17%; Rider 2 - over estimate 12%
iBike - Rider 1 - under estimate 11%; Rider 2 - over estimate 5%
Polar - Rider 1 - under estimate 6%; Rider 2 - under estimate 15%
Test 4 - Crit Racing - Race 1 20min +2; Race 2 15min +2
iBike and Polar had some technical issues for various reasons in relation to fitting units, etc.
Polar again showed that it was a bit slow to pick up the quick surges, etc and showed a lower overall average power value as a result.
Powertap was similar to SRM, but did miss a couple of high value spikes.
Ergomo had a similar result in relation to missing a couple of high value spikes, but also showed a high value for average overall power.
iBike again showed that it is high susceptible to having inaccuracies caused by drafting.
The next bit is my opinion on the data
As much as I would love to have a SRM unit, the cost is prohibitive for your average rider.
The powertap unit has the limitation to being restricted to a single wheel, in addition to the cost.
The iBike unit would not be able to provide any group or race data, which I consider a limitation.
The Ergomo unit is quite expensive when you consider the cost of the unit and the fact that it will require physical modification of the bike to install. In addition restricts the type of cranks that you can use.
Polar, while not perfect, is still the best option. Its consistent in its measurements, works in a variety of environments and is relatively cheap. I know a number of people who use the old style of power unit for the S series of monitors and have had little trouble once set up correctly.
Hopefully my new CS600 with power arrives soon, bike shop was told today by the distributor that I will most likely have to wait till June