Computrainer vs. Powertap Watt Readings

I don't have a PT but I have an Ergomo.

I find that below 100 watts on the CT the two readings don't agree very well.  But once you get above 100 they seem to match.

In general, I see higher wattages outdoors on my Ergomo than indoors on my CT.  I think this is a function of "having to" push the higher wattage to get up the hill, into the wind, etc. and not having the CT calibration set high enough above 2.0.  Anything with a lot of watts (like hills) on the CT I guess the calibration needs to be set higher or your tire slips.

For consistancy sake I always use the power data off the Ergomo....

My Ergomo always seems to be about 20 watts higher than my computrainer.  But I am not really obsessive with accurately calibrating the CT according to the manufacturer's recommendation.  I tend to just turn it on, spin it up and do the quick calibration instead of warming it up for a bit.  I'm pretty sure that makes for quite a difference.

In the recent time trial we did on the CT at the Boston Tri-Expo, my average watts on the CT screen for the all out effort were only around 221.  I find this pretty low for the effort that I put out.  My Ergomo reading was 272 watts.  I tend to trust the Ergomo much more than the CT.