Any ideas what I am doing wrong? I have been just riding it for months knowing that the numbers have to be wrong. I have had a powertap on my bike, so I have an idea where I should be.
Any help would be appreciated. thanks guys.
Have you fooled around with the pressure on the back wheel and tried to sync the two?
Do you properly warm up your wheel and calibrate each time? If so, the watts should not be terribly different.
The actual wheel speed that the system is reading is probably dead on, but this is kind of meaningless since your bike isn’t moving. Now the watt conversion to the road speed based on your drag factor needs to be adjusted so that it matches what you have on the road (along with your weight being put in so speed is adjusted accordingly going up hills).
Any ideas what I am doing wrong? I have been just riding it for months knowing that the numbers have to be wrong. I have had a powertap on my bike, so I have an idea where I should be.
Any help would be appreciated. thanks guys.
Why do you think the CT numbers are wrong and the powertap is correct? Did you calibrate the CT after a 10 minute warmup? Did you zero offset the powertap?
Speed is meaningless on the CT. If you are in erg mode and shift gears the same effort will show a different speed.
Every CT I’ve ridden (5) reads ~50 watts higher than my PT’s (3)
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I hope not 
…although I’ve been riding mine on a wheel that needs trued (hops and side wobbles)…that may be the equalizer.
To the OP, I’m guessing you aren’t talking about erg mode. Did you go out and do the “fake” cda test to get the wind resistance correctly? Does it matter what your speed is on it? There are some groups that do virtual time trials on the CT, you should go look up the settings to get something consistant/repeatable and ignore what the powertap is reading while indoors.
Any ideas what I am doing wrong? I have been just riding it for months knowing that the numbers have to be wrong. I have had a powertap on my bike, so I have an idea where I should be.
Any help would be appreciated. thanks guys.
Why do you think the CT numbers are wrong and the powertap is correct? Did you calibrate the CT after a 10 minute warmup? Did you zero offset the powertap?
Speed is meaningless on the CT. If you are in erg mode and shift gears the same effort will show a different speed.
x2 - i calibrate at around 2.25 on CT. My Powertap and CT are within +/- 2 watts in erg mode. For speed you will have to adjust the drag factor, but I agree with packetloss its meaningless.
The simply truth is that power meters aren’t necessarily all that accurate and don’t need to be. They only need to be consistent.
If you’re training with power than speed is meaningless.
I have a CP set up and a Quark on my bike. It is pretty common that there will be a difference in the measurement. I will regulary perform power tests on one or the other depending on what is appropriate for my current training cycle. Power output ranges just don’t change that much that quickly particularly when you’re dealing with such broad ranges as a 1 to 5 scale.
If you’re really jumping back and forth between the 2 than do alternating power tests every 3 weeks.
The simply truth is that power meters aren’t necessarily all that accurate and don’t need to be. They only need to be consistent.
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That is completely incorrect. If they aren’t accurate you can’t compare data between the two or when you get a new one. They need to be precise and consistent
There is a difference when power is being recorded on a stationary bike vs on the road. I have an article that discusses the differences between the 2 settings. If I can figure out how to upload it to ST, I’ll share it. Although I think I read that we are only supposed to post a link, not the entire paper.
I agree with you, since I work in calibration I know that while consistency is important, accuracy is needed to make good decisions.
It’s difficult to make projections from inaccurate but consistent data.
A link to the abstract or a citation would be appreciated.