Power meter offset

I’m using PowerTap P1 pedals, what should the calibration offset be for the most accurate data? I didn’t do a zero offset through the powertap app before riding and the offset in the TR app was ~230. It felt way too easy pushing Watts well above my threshold.

So I hopped off, did a zero offset in the powertap app, then calibrated in TR. the TR offset then read 10. This felt much more inline with my ability during the workout. Does that sound right?

And since I’m using the pedals I had the trainer (wahoo kicker snap) in resistance mode set at 25%. Is that where the resistance should be?

I usually see a range between 16-22 for my P1 zero offset.

As to Resistance setting, that is purely up to you and the power you need to hit. If you can hit the highs and lows, you are good to go. Is there a reason you are doing Resistance mode instead of ERG?

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I figured that’s what I should do if I was using the power from the pedals rather than the smart trainer. Should I keep it on erg even with the pedals?

You can chose the mode (Resistance or ERG) to meet your preference or needs. It is nothing to do with the presence or lack of a power meter in the mix. If you are unfamiliar with ERG mode, please watch this video to learn more.

The one consideration with a power meter and smart trainer, is whether or not to use the PowerMatch feature in TR. Read the following article to learn more.

Do you have a good resource explaining what the “offset” means? When I calibrate my left sided stages PM TR always give me a value of 868.

I didn’t have anything in particular on hand. Here are some results from a quick Google search.

https://support.stagescycling.com/en/support/solutions/articles/1000046294-what-is-zero-offset-calibration-

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A lot of folks run calibrations until they get offset values that are the same or very close between two calibrations. That might mean running a handful of calibrations prior to each ride. I generally try to get the same value twice in back to back calibrations, but on my V3 pedals we’re usually talking +/-3. My old PowerTap hub didn’t actually give me a value at all… I’m sure it’s different for different PMs.

Wow, I’ve been using PowerTap P1S, left sided, for a couple of years…my offset reads between 7 and 13 depending on the temperature (it seems).

Are you spinning the pedals manually to wake it up, then levelling them before you run the TR calibration?

My understanding is that this process is not true calibration, it is measuring any residual reading when the pedals are not in use. Then offsetting further readings to eliminate the false values.

Correct, what we do on a daily base is actually called the “Zero Offset”.

Actual “Calibration” requires special process that often include a very accurately measured weight applied to the power meter. This is not commonly available and is usually best left to the manufacturer, if it needs to be done after the initial purchase.

Edit: I will add that reading the first link I posted above goes into greater detail for those interested.

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The number value you get once the zero offset is done is particular to each device. My P1’s will not necessarily return the same value as yours however, the value shouldn’t change drastically each time you zero it.
On your case it sounds that 10 is the good value.
Whenever you zero your pedals and you get some value too far away from that, just do it again until its back to somewhere around 10.

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Awesome, thank you! Definitely seems like I didn’t do it properly the first time.

I spin them manually, get off the bike and set my PM to the 6 o’clock position per Stages then calibrate

I get a very similar value, fwiw. And calibrate it with the same technique.