I currently train and perform testing on a PT Pro/32h Open Pro wheel. I am about to get another PT wheel (PT Pro on deep carbon tubular rim) for road racing/time trialling.
What do I need to take in to consideration when training with one/racing with another in terms of comparing AP values? 😕
For example, if I perform FTP testing on my training wheel, should I use the power level values that gives when racing on the other wheel or do I need to test on the racing wheel as well (or instead)?
What do I need to take in to consideration when training with one/racing with another in terms of comparing AP values? 😕 ...
You should do a static torque test(stomp test) on both wheels to find out the accuracy of power measurement from each of the PT hubs. Here's a link to the test: http://www.midweekclub.ca/powerFAQ.htm#Q23 I strap a toestrap tightly around the rear brake to hold the wheel still while doing this test (after spinning the wheel to wake up the PT and zeroing the torque) and do this on a trainer. I like using weights, but have done it with body weight as well by balancing on one pedal.
Differences in power readings from the hubs will be proportional to differences in the torque test results. If there are big differences you should probably have the offending hub serviced, but you can adjust the way you read power based on the torque results. There's no way to actually calibrate a PT at home, the best you can do is become aware of any innacurracy and mentally adjust your readings.
My race and everyday hubs are within a percent of each other (.98, .97) so I don't worry about it much. My everyday wheel set reads lower (.97) so if I wanted to normalize the power readings I'd treat power out of my day to day wheels as watts/(.97) or watts*1.03. Then I'd have to normalize my race wheels the same way: watts/(.98) or watts*1.02. Frankly I just use the numbers as I see them on the display and in CP knowing my real numbers are just a tad higher (and higher yet since the PT is a rear wheel instead of crank based system).
You should do a static torque test(stomp test) on both wheels to find out the accuracy of power measurement from each of the PT hubs. Here's a link to the test: midweekclub.capowerFAQ.htmOpen ↗ I strap a toestrap tightly around the rear brake to hold the wheel still while doing this test (after spinning the wheel to wake up the PT and zeroing the torque) and do this on a trainer. I like using weights, but have done it with body weight as well by balancing on one pedal.
Differences in power readings from the hubs will be proportional to differences in the torque test results. If there are big differences you should probably have the offending hub serviced, but you can adjust the way you read power based on the torque results. There's no way to actually calibrate a PT at home, the best you can do is become aware of any innacurracy and mentally adjust your readings.
My race and everyday hubs are within a percent of each other (.98, .97) so I don't worry about it much. My everyday wheel set reads lower (.97) so if I wanted to normalize the power readings I'd treat power out of my day to day wheels as watts/(.97) or watts*1.03. Then I'd have to normalize my race wheels the same way: watts/(.98) or watts*1.02. Frankly I just use the numbers as I see them on the display and in CP knowing my real numbers are just a tad higher (and higher yet since the PT is a rear wheel instead of crank based system).
