Power match differences

I’ve recently turned on power match between my stages gen 3 and cycleops Magnus trainer.
I’ve noticed that there’s often a large gap between the power my cranks read and what the trainer shows.

So much so I had to set the power match off on Saturday and today’s efforts as it killed me.

I regularly calibrate my crank in the tr app and do the trainer in the Rouvey app (only way I believe I can do this?). I don’t think I should need to calibrate the trainer every time?

I’m connecting via bluetooth to my phone and it’s in the device page when pedalling that I see the difference in power. Is there anything else I can try? Or just stop power matching, but as I understand it that will give me a good ftp total I can use outside for pacing as well as training indoors.

I should say I’ve contacted support (and replied on a random trainer post) but I thought with people having similar issues would be worth a punt here too.

Wrong. Saris suggests a calibration for EVERY ride.

It’s this varied rolling resistance that the roll-down calibration is measuring and accounting for when calculating power readings, or wattage. Since rolling resistance can change from session-to-session, or even within the same ride, we recommend performing a calibration as frequently as you wish to keep your power numbers as accurate as possible.

  • Implying to do it each and every workout.

This is common practice for all Wheel-On trainers from every manufacturer I have seen. I know some don’t do it, but skipping it leaves the potential for more variation in power reporting from the trainer.

What are you trying to accomplish here?

  1. Assuming you are OK with the performance of PowerMatch, keep using it with the trainer and power meter.

  2. If you plan to ditch the power meter and use trainer power, just do a new Ramp or FTP Test and work off those values.

  3. It’s understandable to want both devices to track with similar numbers, but if you look around, you will see that gaps are possibly the norm than super close matching. There’s a wide range of experience in trainer vs power meter data. Skim this Equipment category with Power Meter and Trainer as the tag (just like yours) and you can see plenty of examples with varied results.

Was your last FTP test done with power match on? (meaning the stages determined your FTP - not the trainer power?)

If not, I’d say just re-test FTP using the stages in power match and see what you get - it might be quite different, but will then reset your zones correctly.

I have a SNAP wheel-on and could care less what it says and don’t bother calibrating it - I just rely on my stages which is way easier, and then matches up outside.

I also have a Kickr snap and I calibrate it every ride although im using my Vector 3 pedals as the power source. Are you saying that calibrating the trainer doesn’t matter at all?

If you use Power Match (via TR or the Wahoo option), there is less need to calibrate the trainer specifically, because the power targets are set according to the power meter.

The gap between the trainer and power meter will be monitored and adjusted in the workout, regardless of whether the trainer was calibrated or even if the power data is notably different.

With Power Match, the most important thing is to zero offset the power meter so it is accurate.

All that changes if you are using just the trainer for power data. When that’s the case, calibrate each and every ride.

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Yea, it’s not necessary to calibrate the trainer once you use another power source. This makes life so much easier… I can’t remember when I last did a spindown, much less stopping to do another one 10 mins in to account for tire heat!

Frankly I don’t even zero my Gen3 stages that much as it’s very consistent. I try to remember to do so before ramp tests, or if I did some work on the crank. I’ve never had a situation where the meter seemed to read something not believable or found a noticeable shift after calibration. They also have built in thermal compensation. Even the guy from 4iii on the podcast had a hard time making the case that it’s particularly critical… More just a good habit in case you bash it was what I concluded.

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Brilliant! Thanks for the advice y’all.

Guess there is a ramp test in my near future.

8W drop so hopefully I’ll finish the VO2 workouts now without dropping the percentage.