Power meter vs trainer power issues

Anyone else having power issues when using their power meter vs the trainer power?

I have a stages LR gen 3 ultegra power meter and i’m noticing significant issues in power that’s being reported when using bluetooth. For the past few months, I’ve primarily used ANT+ on my mac to get the power from my stages, but because of annoyances of dropouts, I tried to switch to a bluetooth connection based on recommendation by the TR staff.

However, when i used bluetooth i noticed that the power was significantly lower (30w below) what i was used to seeing at the same effort. After several tickets with the TR staff we couldn’t really determine the cause and I decided to stick to ANT+ and bought a usb extender instead so i could put the ANT+ receiver right under the trainer (Neo2).

The other day, i decided to give bluetooth a shot again. At first i tried with the stages PM as the source, but was still seeing the discrepancy in power. I disabled the stages and used the power from the Neo2 and it was on point with what i was expecting.

Has anyone else had this issue? Any one else with the same setup (neo2 and stages LR)? In this scenario should i then just stick to the power from the neo2 instead of the stages?

For reference, i don’t see issues with the power meter when i’m riding outside (although that’s reported via ant+ to my garmin).

Thanks in advance all!

I might have misunderstood your issue but I would stick with the Stages / Power meter, especially if that is what you use outside.

What do you mean…

was the Neo a higher number by any chance, if so why would you trust that anymore than the Stages?

A Stages LR on Shimano can be a tricky beast due to Shimano variances that @GPLama has outlined pretty well. I’d absolutely trust the NEO over the Stages LR.

That said, it’s not clear if the Stages LR is higher or lower than your NEO from your post. However, Stages should be higher, but not likely 30w higher. If looking at something like 250w, I’d expect stages to be between 5-8w higher assuming a normal level of drivetrain cleaning.

For troubleshooting power meters and trainers, I also wrote up an entire post that dives into this in way more detail than you’ll ever really want: https://www.dcrainmaker.com/2018/12/how-to-troubleshooting-power-meter-and-trainer-accuracy-issues.html

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That makes sense I think.

It is not clear what the power source in regards to the -30w but reading again the suggestion is a different in readings when using bluetooth?

Different readings on BT are actually entirely plausible. Specifically with dual-sided cranksets. There are cases where either an app or the crankset can single-channel stuff incorrectly.

The easiest way to validate/check for this is to ensure that the device recording is showing a left/right balance somewhere. When I’m doing testing with dual-sided devices, I always keep a data field handy that shows that - just as a quick double-check that I’m getting data from both devices. BT supports this, but many times apps don’t. In that case, they can sometimes only connect to a single side of the power meter, producing funky results.

For the NEO - there’s no scenario I’m aware of in which that kind of split can occur. It single-channels everything.

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the neo had the higher number.

  • neo2: 100w at 98rpm
  • stages LR: 74w at 97rpm

thanks! i’ll read through the article and see if that helps.