harringtonp wrote: » Its only numbers but it does mean that for any interval work you have to rediscover the numbers for the particular intervals.
harringtonp wrote: » I am comparing a right side spider with a left side crank and the left leg right leg discrepancy is undoubtedly a factor. It's not scientific but blatantly obvious from examining the image above that the 4iii reads way lower than the P2M. This is not an isolated case either, every time I use it numbers or lower.
Daroxtar wrote: » My FSA Powerbox (rebadged power 2 max) measures lower than my smart turbo. Similar to about 200w but after that there's a steady creep, about 10% difference so 400w on the FSA is closer to 450 on the turbo but strangely in a flat out sprint the FSA usually shows a higher maximum output
tunney wrote: » Whats the smart turbo?
Daroxtar wrote: » It's a Tacx Vortex smart.
doozerie wrote: » For what it's worth, my dual power meter pedals show my (averaged) left/right power balance as 45%/55% at its worst. If I was using a single-sided power meter then my estimated average total power could obviously differ from reality by quite a bit - it would potentially show 90% of actual power if mounted on left, or 110% if mounted on right.
Macy0161 wrote: » If the power meter is consistent, does it really matter? I only really use power when training or analysing after the fact. I'm happy enough with the limitations of my left only power meter to be honest, particularly when it matched the total "power" of my Hammer. Or rather I can't and couldn't justify the cost of total or dual power meters.
doozerie wrote: » However, if you are swapping between two or more power meters then it becomes a real pain if you have to mentally (or via software) adjust for significantly different readings for each, even if each of those meters is consistent in itself. It could even hamper your training if you get that adjustment wrong between meters.
harringtonp wrote: » This is the crux of the issue. Lower numbers in particular mean getting new numbers for intervals, higher isn't so bad. If I was doing 6x3min on the road tomorrow using the p2m I'd be looking at averaging 330-340 for each interval. If I was to try this with the 4iii I suspect I would blow after 2 intervals. And that's the same for every interval length. And when I blow a session I then have to figure out if and how I can rescue it as there is a strong urge to just bail.
Lumen wrote: » Can you anticipate and therefore avoid the blow up using HR? Or does that remove the whole advantage of a power meter?
harringtonp wrote: » BTW I haven't done a proper FTP test in years. If you use power meters a lot and maintain a fairly constant level of fitness during the year they are of limited value.
tuxy wrote: » Have you tried changing the scale factor like 4iiii support recommended? It would be interesting if your numbers come closer to matching up after that.
doozerie wrote: » Re Erg mode, if you are measuring FTP via a ramp test then I'm inclined to think that Erg mode won't skew things at all. If doing a more conventional FTP test though then I think it might affect the results. Re big versus small chainring, I've read some very determined claims online that you'll get different power readings for the same "level of effort" in big versus small chainring on a turbo trainer. I've certainly read convincing conclusions from tests that measured different power losses between big and small chainring due to differing amounts of chain articulation, the wattage differences tend to be in single digits, but the other (less convincing to me) claims I refer to have talked of bigger differences. I wonder whether the differences you are seeing has anything to do with inconsistent measuring of cadence though? The reported power figure is calculated by torque multiplied by cadence so variability of either torque or cadence will obviously affect the power figure. The reason I focus on cadence is because I've had trouble with my Neo spiking to crazily high cadence figures at times. This happens in my power zone 1 primarily, tends not to happen at higher zones, but when I raised the issue with Tacx they basically told me that cadence figures reported by the Neo are calculated ones, it doesn't have a conventional cadence sensor built in, and essentially I've just got to live with its unreliability (my word, not theirs). Not very reassuring for such a premium product. I was left with little faith in the ability of the Neo to correctly determine cadence generally. As an aside, since then (a few months ago) I've been using my bike's Garmin cadence sensor as the source of cadence measurement, ignoring the Neo's cadence figures, and my reported speeds for turbo sessions are noticeably lower than before. Not that it matters as such, I don't care what theoretical speed I'm doing when stationary, but it leaves me wondering how the Neo determines speed too.
Crocked wrote: » I had read some debate online regarding big v small ring and the RPE and did find that myself. All my indoor training throughout winter was done in erg mode and small ring with no outdoor rides in that time. It was noticeably harder to do the same intervals in big ring when I decided on a whim for ****s and giggles to go mad one night and use the big ring for a set a few weeks back. So much so I failed and bailed on a few workouts. This seemed to level off after mixing things up for a few sessions and I found my big ring legs if that makes sense.
Crocked wrote: I have noticed a difference in the cadence but my understanding was the neo didn't use cadence in it's power calculations so disregarded it as a cause.
doozerie wrote: » Every time I try to get my head around this I completely fail, I might simply be missing something blatantly obvious. My brain tells me that if I choose a gear combination in big ring that is essentially the same as one in small ring, and I keep cadence the same in either gear (so that power output is the same, which means torque must be the same), then the effort I'm putting in must be the same in either gear. But I've encountered several online discussions where people were very adamant that even keeping cadence and power the same on the turbo, the big ring gear made for a much harder session. When you tried your sessions in big ring did you use the same cadence as you'd been using in small ring?Yeah I'd never even considered it a thing until I changed chainring and was wondering why my workouts went to ****e. I'll have to double check but cadence in big ring from memory tends to settle in around 90-92 whereas small ring i tend to settle in around 93-95 so not a massive difference. It definitely feels different though, small ring feels a bit heavier or less smooth in a lower cadence ( i used to have lower but I've naturally seemed to moved up to a higher cadence in the last year maybe due to the small ring workouts feeling a bit heavy at the lower cadence?). I'm guessing it's just flywheel inertia/speed or something along those lines but this kinda stuff is above my pay grade. I now mix and match rings a bit and I can do efforts in either ring but they still feel different to my legs/head. . This fits with my experience too. Whenever my cadence, as reported by my Neo, spiked it never affected the power figures, even if the cadence spike lasted a relatively long time (30 seconds or more). I saw the same cadence spikes across two different applications so they were definitely coming from the Neo. If the Neo had been calculating power based on torque and cadence, which is how I understand most power meters calculate power, then its power figures should obviously have spiked too. Which leaves me wondering how it actually calculates power. That hurts my brain too.I've never noticed the neo cadence spike like that and thats the cadence I have showing on my workouts but can't remember ever seeing it look weird like you have had. I think the neo is using the magnets and the power to them to calculate the wattage so cadence to it isn't important. The powertap hubs estimate cadence too so likely they are calculating power in a similiar fashion?
doozerie wrote: » If the Neo had been calculating power based on torque and cadence, which is how I understand most power meters calculate power, then its power figures should obviously have spiked too. Which leaves me wondering how it actually calculates power. That hurts my brain too.
