Rally XC100 and Edge - Calibrate before EVERY ride necessary?

You can also enable auto-calibration. In this case the pedals will calibrate automatically if certain criteria are fulfilled. 

The pedals will calibrate if:

- the pedals are unloaded 

- the bike is relatively upright 

-  the pedals will calibrate before turning off and just after turning on. 

Thanks, Jason. I will give that a try later today. 

I presume the option for enabling auto-calibration is in the Edge GPS unit?  

I did it on the Garmin Connect app on my iPhone.

You should still calibrate manually before a ride according to garmin. Especially if you move the bike and there’s a difference in temperature 

I live in an apartment so the temp for the bike changes immediately when I head out. Based on DCRainmakers review, they don’t do a good job of auto calibrating in this case. Garmin specifically tells users to calibrate for big temp changes. 

if the bike were outside for a while before riding then it doesn’t matter as much. 

calibrate it inside before the ride and problem solved 

but my opinion the best way with Rally (or with any other pedal based system) is the constant calibration before every ride , do not trust in Garmin auto features  (i had garmin powermeter in the past, no more :) just spider-based Power2Max NGs in my all bikes since 5 years, that is pinpoint accurate with real auto-calibration/zeroing, the other meters are not really... )

Nope. That’s the actual problem, the auto calibration isn’t great at large changes in temperature. That’s basically all year for me since the apartment is rarely a similar temp as outside. 

from garmin:

“For the best results you will still want the bike to have fully adjusted to the temperature it is in and then do the zero offset calibration. We expect that to take about 10mins per 10°C. If you were to calibrate immediately, you would be setting the zero offset based on a temperature that’s likely much closer to what it was inside.

There is a difference between our zero offset calibration and temperature compensation. The zero offset is influenced by temperature at the time it is done which is the meaningful difference we expect between your rides after looking through the data. Our temperature compensation is then used to ensure we maintain that offset throughout a ride if the temperature changes to protect against drift.

Additionally, our Auto Cal feature does have some limits on how much it is allowed to change the zero offset which we believe you would have been outside of from your outdoor to indoor ride. The reason for that is we do not want to accidentally get a bad zero offset in the middle of a ride if the customer stops and happens to say, have one of their pedals leaned up against something.

Like I said, this is an area I’d like to improve going forward and we have some ideas around how to do so. I don’t want our customer to need to know all of this and even more importantly, we want to do everything we can to prevent a ride with inaccurate power data that can then influence the rider’s training guidance and our quantification of their fitness.

if you calibrate it inside then the active temp-compensation will handle the temp change outside and the power measuring will be correct during the ride . if you carry out your bike from inside to outside and calibrate it immediately, that is a mistake (as the Garmin wrote), because the strain gauge is cooler than the ambient temp by temp sensor and it causes under or overmeasuring with an offset value (10-20-30watt +- apprx) and you must stop after 10mins apprx and rezeroing it for accurate measuring. so best to manually zeroing it and inside in your case

but this is why i suggest to avoid the pedal power meters and using only spider based P2M (trust me , i'm power meter expert since ~10years with tons of pmeter experience :) )

Interesting. I'd love to test this out but I'm not sure I have the tools since I only have the pedals.

I agree on other types of PMs being better for this but I chose pedals specifically for traveling and to have a less invasive install on the bike.