So this is something that has been perplexing me now for a while without much noticeable impact but it appears to be worsening over time and with the nicer weather meaning more outside workouts, it is impacting my training, which isn’t ideal.
I’ve been running a left-crank Stages G2 (bought used) for 18 months or so now and it’s been fine, no doubt better than the wheel on cheapy turbo I had initially. However, it seems like something isn’t quite right with it any more, it’s either started under-reporting power over time, or I’ve been slowly de-training over the last while (despite being measurably faster etc). My FTP by the Elite Direto PM is ~315 whilst the Stages FTP is 273 by my last ramp, 12 W down on my post-Winter FTP, also on the Stages.
I’d have thought the offset here would be the other way around, with drivetrain losses etc. Regardless, that’s still a big offset, even with doubling of left leg etc etc.
It gets more perplexing looking at the five main intervals, where the Stages reported power tails off as the interval continues. This ends up about 40 to 50 W difference, the same happens in both ERG and slope mode.
This means when I head outside I end up cooking myself depending on the session, and not able to workouts later in the week. Ideally I’d be using Power Match, but I feel like the Elite swings wildly trying to keep up and it’s unusable.
It doesn’t stabilise over time, there appears to be no effect of temperature, cadence or zero-offset changing. I’ve removed and inspected the crank and no damage is visible!
Is it time for a new power meter? I’ve contacted Stages, and will see what they say but I’m keen to see if anyone else has seen this sort of drift before?
First thing I would do is some left leg only drills, double the power of the trainer - are the curves closer? If yes might point to left leg being weaker.
Having said that, I had a stages and eventually its power values drifted and they confirmed could not be repaired. In my case the calibration values started drifting down over time.
Not had my Stages drift but I can tell you that I did have a left/right imbalance (verified by 2 dual sided PM’s) and using a left only Stages indoors with Neo2T/Powermatch has enabled me to correct it (mostly)
I would also not trust the power readings from anything other than an actual PM (most trainers read too high imo and experience using 2 wahoos and the Tacx)
But if you get zero offsets that’s are way out then it could be the strain gauge, I’ve had 2 singles and one dual replaced because of drift in zero offset.
I have a left sided stages 3rd gen and a directo. I always record both power sources separately (stages to 945, directo as the power source I use for the workout). I don’t use power match.
Depending on the day, the NP can be the same to 10 watts difference. The majority of rides it’s within 5 watts. For us amateurs, I think that’s fine.
Generally speaking, the stages is the source that trends higher for me.
I did think that, but then that would mean somewhere around a 40/60 L/R balance, that’s got to be something I would have picked up on by now or have one monster leg!
There is an actual PM inside the Elite Direto, it’s an optical torque sensor, think it works by measuring deflection of some metal disc inside. Reportedly properly accurate!
I went back to see if this is something I’d been seeing for a while and just not feeling, but it seems like before they were close enough. This is a Petit from late March with form sprints.
I would be more inclined to believe the Elite, it’s new, has an actual PM in it with it’s optical torque sensor magic. Obvious caveat of newer isn’t always better, but the Stages has had a tough life, running a cross season and a full UK winter.
Have the Stages calibration readings remained the same? My Stages reads lower than my Saris H3 by 2-4% but calibration is consistent and this difference is within spec of both units accuracy. The issue I have though, is that by the nature of how the Stages measures my power output is much more variable than the Hammer and this harder to train with. I used to have to concentrate on power stroke much more and often had to chase power targets. With Hammer I just pedal and get on with it.
Guys i’m not sure but I’ve been having my suspicions about my Gen 2 Dura ace Stages. I found that if I zero on the stages app it gives total different offset values than on the calibration on TR. Anyone else find this?
Thanks for the info on the Elite, I did not know it was an actual PM.
If you can’t complete outside workouts using an FTP from your trainer surly the FTP is too high? Have you tried altering the FTP to match what you got from the Stages ramp?
I find that for outdoors riding a PM discrepancy makes less difference (I also have a 4iiii that over-reads which I’ve now offset to give lower readings) as power on the road is so highly variable riding to 2-5% wattage margins is just not possible anyway. This is where having a sense of RPE for a given power and monitoring HR is important IMO.
