Getting accurate TSS with power meter discrepancy

New trainerroad user and new stages power meter owner. My apologies if these questions and concerns have already been addressed.

I have recently purchased a L crank arm power meter that I will be using on both my gravel and road bikes for outdoor training. I do about 60% of my training inside on a Cycleops Hammer trainer with an old dedicated trainer bike that does not have a power meter on it. After I received my new meter, I decided to use it on the trainer for one ride to make sure there wasn’t a huge discrepancy. During the workout, the stages was reading roughly 10% lower than the hammer trainer. For future trainer workouts, I do not plan to use my on bike power meter. My questions are:

  1. Is it possible to change the power readings on trainerroad to match my power meter readings without changing the effort?

  2. Should I retest my FTP with the stages connected and powermatch on in order to get a more accurate number that I can use outside? If I do this, will the power numbers continue to be deflated to match the stages if my stages isn’t connected on future workouts?

  3. Is there a way to manually inflate my numbers on the stages in order to match my hammer during outside workouts?

I recognize the easiest method would be to make a mental note of the difference and then perform the workouts only meeting 90% of the target power for prescribed intervals, but I also want my TSS and IF to be accurately reflected outside. Thanks, everyone.

Of course, it is the Stages reading low, rather than the Hammer reading high. :laughing:

That said, it may be worth checking this discrepancy in more detail (eg. does it hold true across all parts of the power curve).

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Not sure which is high or low. That is why my first question was whether I could deflate the TR app numbers a bit to match the stages. I have had knee surgery in the past year on my left leg, so that could be one reason for the number discrepancy. Or my trainer is boosting my ego. With a couple of TT events later in the year, I’m only chasing consistency in power and TSS the more I begin doing outside workouts.

The number difference seemed to be somewhat consistent throughout the power curve. Intervals of about 5 minutes avg 220 on TR read around 195-200 on the stages. At 300, those numbers were between 265-275.

My N1 thoughts.

I’ve never used a stages but use a quark and calibrate it as recommended. I would assume the stages has some sort of calibration in a certain position else this probably isn’t a good idea?

Adding very light weights to the pedal if its calibrated in the 6 o’clock position, this may move the power curve in a direction?

Maybe try moving it’s position to another when calibrating, thus weight, say to the 12 o’clock position and it may “calibrate” with the offset you desire, again weights may be required or helium balloons :sweat_smile:

This is something you could quickly try and something that can be quickly reversed if it doesn’t achieve the desired outcome by calibrating it correctly.

Really no idea what would happen to all parts of the power curve but at least you can test it against your trainer there.

Hopefully someone may come up with a better suggestion…

I have a similar issue with my favero assioma uno (one sided). In the favero app you can adjust the readings by a percentage (since my favero is reading high I reduced by 4%). Check your stages if you can make a similar adjustment.

I would recommend doing several calibration rides with power meter and trainer to tune in the adjustments.

Consistency is more important than accuracy.

Use the PowerMatch feature in TrainerRoad which is described Here

This way you will always get the readings from your stages PM and the workout will be controlled by the stages through the Hammer unit.

Thanks. I will look into that with stages. This would be the ideal scenario, outside of getting the ride aided component.

I understand that powermatch would be a great option and would clear up the issues I’m having with consistency, but the problem is that I have a dedicated trainer bike that doesnt have the power meter attached. It’s also in a location that makes it quite inconvenient to take on and off. I’ve only used the stages initially to see the power discrepancy.

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Your other option would then be to run a test with both trainer and stages at the same time. Use a power analyzer tool like DC Rainmaker’s Power Comparison Tool to see what the true discrepency is over a few power ranges, and then use the manual offset feature in the stages app to see about equalizing the two.

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Thanks for the help. I haven’t gotten the app yet but happy to hear there is a manual offset option. Looking at the backlog of issues found in this forum, it seems like everyone generally has issues with the stages reading High because of drivetrain loss, and can manually adjust the crank arm length shorter to affect the power readings lower.

Did some outside “testing’’ yesterday with a teammate. Same bike, wheels, clothing. Both Pms calibrated. We decided to roll the same uphill strava segment and look at the power numbers after. He was pushing 5 watts higher and I’m about 20#s heavier. Too many confounding variables to look too deep into it I’m sure, but does seem to further indicate low readings.

Please use the DCR power comparison tool.
Comparing your PM to another owners bike PM is just adding one more variable to the equation that is not controlled for. If you want reliable consistent results that is not the way to come at the problem.

I’ve had a Stages gen2 and gen3. Compared against Kickr 2017 and used the DCRainmaker power comparison tool. What I found is that the Kickr power estimation varies based on temperature, so over the course of the workout it changes a bit. I had suspected that because some of my initial TR workouts seemed harder at times.

Ok, so to deal with the time varying power readings on the Kickr I did a spin down after 30 minutes, and then the Stages and Kickr were within a few watts of each other. All good. And with only 1 bike everything was resolved by using PowerMatch so that indoor and outdoor power matched.

I understand you are a) using another bike on the Hammer so no PowerMatch, and b) my experience with Kickr doesn’t translate to Hammer. Also it was suggested to use an offset feature in Stages app, that is a feature I haven’t seen on iOS and I don’t think is available.

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I also have a difference between stages left cranks which I have on 4 bikes and my tacx neo. I ramp test on the neo and over the course of months and years based on rides and testing I’ve honed in on a 30w greater FTP to use outdoors with the stages. Using the higher FTP then automatically adjusts all my workouts and stats when I’m outdoors. I also have to manually edit each outdoor ride FTP after its uploaded on trainer road, easy to do that so no big deal. I should mention I also use a different FTP because I can put out more power outside, due mainly to increased cooling I think, its not just the power meter difference. If I didn’t have that difference it would be an easy solution to just put a stages on my trainer bike. No way to know which is one right and it doesn’t matter, just needs to be consistent similar effort level even if the value is different.

The things you are asking about generally aren’t possible so using a different FTP is the best solution I can think of. They’ve mentioned and there is a forum post that having multiple FTPs in the app is a possible future feature.

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Because stages is lazy and wont include like 4iii or favero you have to do workaround by adjusting crank length

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Yeah, I was not remembering a direct option for power offset in Stages app either.

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Brilliant. I did not realize there was a feature to have different FTPs for different workouts. I’m assuming that doesn’t fix the issue of TR workouts outside giving me trainer watts rather than outdoor watts, but does fix my TSS issue. I’m happy to take the time once a month to bring in the stages bike to perform the ramp tests. Thanks! Eventually when I get out of school and find a job I’ll just spring for a spider based PM and save the headache.

For outdoor rides you change your ftp setting in the app before changing the workout to an outdoor workout. Then it will upload the workout with the outdoor ftp you want. Its just a bit annoying that have to keep changing the ftp up and down so your ftp tracking history doesn’t mean anything. But its better to track all your improvement, weight, etc in your own spreadsheet anyway.

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Not to mention that depending on the final Adaptive Training implementation, changing your FTP can sometimes trigger adaptation to the workouts, so that could lead to quite a mess if that happens each time you swap for whatever reason.

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Yeah, a large decision in me even getting a PM was for the AT rollout so I could get the benefit input from my outdoor workouts. Previously I’ve just been completing outdoor workouts with HR and RPE with pretty good success. So, if I’m planning on using AT, I may be resigned to waiting to get a slightly more *accurate PM that tracks more closely with my trainer.

*I recognize the PM is accurate and that it is a physiology rather than a hardware problem. Nothing against stages.

There have been other posts dotted around the forum about this issue and on one of them someone from TR said, if I recall correctly, that putting a manual offset function in the app to adjust the reported power to match your primary power source was something they are considering doing. Whether they will or not - who knows? We need to call it something other than “matching power” because as soon as a lot of people see that they just think “Powermatch”, which it isn’t.