Hey
I've been happily training with an ergomo this winter for the last 4 months or so. Readings seemed realistic, reliable and very repeatable, all was well. Until I got a powertap SL, planning to move the ergomo onto my TT bike for the racing season and use the powertap on my training bike. I figured I might as well use them both on the training bike for a while to calibrate them against one another before moving the ergomo - after all I know the powertap is supposed to be a few watts lower than the ergomo due to drivetrain losses, and also I'm realistic and was prepared for the possibility of some non-linearity in the relationship between the two readings.
What I wasn't prepared for, and am rather upset by, is what seems to be a definite time-drift between the power meters. First of all the PT reads higher than the ergomo- surprising, but I could deal with it. It seemed about 10W higher. But over an hour's interval session it drifts up. I've attached a picture of a typical comparison - by the end of the last rep the PT was reading up to 50W higher at times than the ergomo!! Clearly this is too much to be tolerable. A session done at 'constant power' on the ergomo is going to be a very different session to one done at 'constant power' on the PT.
So what do I do? I have as far as I'm aware no way of determining which meter is the accurate one. My gut instinct is that the PT is reading high, but that could be just because I'm used to the numbers from the ergomo. Has anyone had a problem before with either unit drifting over the course of a session?
Any help much appreciated, am feeling pretty p1ssed off right now and considering going back to training with tarot cards and a heart rate monitor
I've been happily training with an ergomo this winter for the last 4 months or so. Readings seemed realistic, reliable and very repeatable, all was well. Until I got a powertap SL, planning to move the ergomo onto my TT bike for the racing season and use the powertap on my training bike. I figured I might as well use them both on the training bike for a while to calibrate them against one another before moving the ergomo - after all I know the powertap is supposed to be a few watts lower than the ergomo due to drivetrain losses, and also I'm realistic and was prepared for the possibility of some non-linearity in the relationship between the two readings.
What I wasn't prepared for, and am rather upset by, is what seems to be a definite time-drift between the power meters. First of all the PT reads higher than the ergomo- surprising, but I could deal with it. It seemed about 10W higher. But over an hour's interval session it drifts up. I've attached a picture of a typical comparison - by the end of the last rep the PT was reading up to 50W higher at times than the ergomo!! Clearly this is too much to be tolerable. A session done at 'constant power' on the ergomo is going to be a very different session to one done at 'constant power' on the PT.
So what do I do? I have as far as I'm aware no way of determining which meter is the accurate one. My gut instinct is that the PT is reading high, but that could be just because I'm used to the numbers from the ergomo. Has anyone had a problem before with either unit drifting over the course of a session?
Any help much appreciated, am feeling pretty p1ssed off right now and considering going back to training with tarot cards and a heart rate monitor