Is a watt a watt?
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Member
376 days
derek5 posted 7 weeks ago.
Ive noticed that on a computrainer your wattage readings will be a little low. Partly because of not calibrating it perfectly and also because you get tired quicker because of never being able to coast. The best way to find out is to use your power tap on a computrainer. Then you can compare numbers so that you get an idea of what your wattage is in the "real world".
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Member
312 days
xc800runner posted 7 weeks ago.
All your power meters will have a variance to some degree. This is due partly to the mechanism that is employed to measure wattage, and partly to the point of measurement. If you calibrate all them to read the same, then they'll work just fine.
Physically, you should get the highest power readings from an srm since this measurement point is the most direct (at the crank). The Polar method of measuring chain tension should be slightly lower to account for the frictional and strain losses in tensing the chain at the chainring and cranks. Powertap will have additional energy losses through the hub and will read lower as a result. Finally, you would have computrainer power at the bottom of the chart since you also need to add in frictional losses at the tire/drum interface. Swap out all your bearings for ceramics and you'll see the largest jump in power on the computrainer, but your overall power savings will be equal. Your srm won't know you did anything.
Are the watts on say a Computrainer measured the same way that the watts from a PowerTap are measured? If I train on a Computrainer can I expect the same measurements of power from a PowerTap or do they all differ slightly (is a watt a watt?) Anyone have any experience with this?