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PowerTap pedals and calibration
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Before I purchased my PowerTap pedals I did some research on here to see how they were. Everyone pretty much loves them, but there was a thread about calibration. It talked about when new, the calibration number was single digits and over time it would climb up into the 40s and 50s (maybe more, can't exactly remember).

My question is what difference does the calibration make? I only ride outside as I don't have a trainer. I installed them this week and calibrated them (double sided) which were 55 and 56. Today they were 44 and 45.

Since I'm not out comparing my power numbers to anyone because mine are so low, I thought the results would be good for training and racing, regardless of the number. So, if my ftp test said 175 I don't really care if that exactly correct. I only care if it doesn't change day-to-day because of the calibration.

If the calibration changes from 55 to 44, does that produce a different reading on the power when riding? If so, is the power reading higher or lower when calibration is 44 instead of 55? If different, is it a percentage (20% in this example) or an actual watt number (10 watts different)?

TIA
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Re: PowerTap pedals and calibration [LEBoyd] [ In reply to ]
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Think of calibrating like zeroing a scale. By doing the calibration, you are getting a more accurate, more consistent measurement. The actual calibration number doesn't really matter, as long as it isn't a crazy number which could indicate a problem with the power meter.

Environmental factors can impact the strain gauges that are used in power meters, so the calibration changing a bit day to day isn't a concern.

TLDR: Calibrate before each ride, and just aim for whatever power output you planned to ride.
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Re: PowerTap pedals and calibration [LEBoyd] [ In reply to ]
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"If the calibration changes from 55 to 44, does that produce a different reading on the power when riding? "


No.
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Re: PowerTap pedals and calibration [LEBoyd] [ In reply to ]
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Just remember to set your crank length correctly on your head unit.
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Re: PowerTap pedals and calibration [bgoldstein] [ In reply to ]
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Thanks folks for the input. I'll just do like I have done and recalibrate before each ride and ride my plan.
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Re: PowerTap pedals and calibration [LEBoyd] [ In reply to ]
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Thank you for posting this. Recently, my P1 pedals went from 15 to 18 when zeroed to 38 to 40 on the left pedals only. It is good to know that this is normal and doesn’t mean the accuracy have changed
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Re: PowerTap pedals and calibration [karmatraining] [ In reply to ]
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“Zeroed”?
Do you mean calibrated or are you doing something after you calibrate?
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Re: PowerTap pedals and calibration [Buchreitz] [ In reply to ]
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I used zeroed there instead of calibrating because it’s not really calibrating unless you are using a defined weight. Yes, Garmin says calibrate but it’s not really calibration
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