Shimano power meter inaccuracy, and assymetry

[eins4eins]

I'm a happy quarq user, but wonder if this whole inaccuracy discussion isn't overrated. Looks like someone wanting some extra clicks for his youtube channel.
Ineos, Bora, FDJ, Jumbo - all using those cranks. If its good enough for them, how big of a problem could there be?

[TobinHatesYou]

I'm a happy quarq user, but wonder if this whole inaccuracy discussion isn't overrated. Looks like someone wanting some extra clicks for his youtube channel.
Ineos, Bora, FDJ, Jumbo - all using those cranks. If its good enough for them, how big of a problem could there be?

If you think GPLama is reliant on YouTube channel views as a revenue stream, then 1) you don’t know Lama and 2) you don’t understand how little money channels of that size make.

[eins4eins]

Yes, don't know all that. But doesn't matter, as my core statement was: how could this be a big issue, if the best professional athletes have no problem with it?
This discussion is totally blown out of proportion in my opinion.

[zirxo]

Because as we saw with Sky and left only Stages, the big teams ride what the sponsors wants them to ride. It's as simple as that.

[Nefarious86]

Because as we saw with Sky and left only Stages, the big teams ride what the sponsors wants them to ride. It's as simple as that.

Then train on SRM and Quarq lol

Sent from my SM-G977B using Tapatalk

[RocketRacing]

Yes, don't know all that. But doesn't matter, as my core statement was: how could this be a big issue, if the best professional athletes have no problem with it?
This discussion is totally blown out of proportion in my opinion.

Power meter accuracy is not that key. You just need consistency. But i figure that if i buy a power meter... i want an accurate one. Or at least shimano should come clean with the true accuracy %.

As someone suggested prior, expect shimano to release symmetrical cranks next gen.

[BdaGhisallo]

Yes, don't know all that. But doesn't matter, as my core statement was: how could this be a big issue, if the best professional athletes have no problem with it?
This discussion is totally blown out of proportion in my opinion.

Power meter accuracy is not that key. You just need consistency. But i figure that if i buy a power meter... i want an accurate one. Or at least shimano should come clean with the true accuracy %.

As someone suggested prior, expect shimano to release symmetrical cranks next gen.

PM accuracy is key unless you only plan to ever use one powermeter. If you ever change PM's don't you want to be able to use your previous power levels as a guide? Is it good if one PM reads 300W as being 280W and another as 310W?

[velolive]

Because as we saw with Sky and left only Stages, the big teams ride what the sponsors wants them to ride. It's as simple as that.

A bit offtopic

[Sockman]

I own a Shimano PM. It reports the same power numbers as my Quarq, my old P2M & my past two smart trainers. Where exactly does the innacuracy come in?

[Alex222]

https://gplama.com/2019/06/29/shimano-c ... er-meters/

Video below
https://www.youtube.com/watch?v=M0tWTUwpt1k

[TobinHatesYou]

I own a Shimano PM. It reports the same power numbers as my Quarq, my old P2M & my past two smart trainers. Where exactly does the innacuracy come in?

Considering you can’t use a Quarq or P2M at the same time as a Shimano crank based PM, how do you even know? Magic?

[spud]

^ you can correlate with the smart trainers

[TobinHatesYou]

^ you can correlate with the smart trainers

As always, not that simple. Testing two power sources at once doesn’t tell you which one is accurate, if either. Removing and remounting a bike can upset a trainer’s calibration. Average watts over an entire ride doesn’t tell the whole story. In other words there is always a doubt over whether the known good quantity is actually good at one time or another.

For a while I was using a pedal PM, smart trainer and a Quarq, all recording to different head units and uploading the FIT files to DCR Analyzer.

More data is better though. If he could run some concurrent tests and FIT files with, say the same ERG workout, I could upload them to the analyzer tool and we could start making some assumptions.

[Hexsense]

I own a Shimano PM. It reports the same power numbers as my Quarq, my old P2M & my past two smart trainers. Where exactly does the innacuracy come in?

They need dynamic compensation. To do so, they need to change offset values based on crank angle multiple time a circle.
And even so, it'll only accurate if your pedaling circle is "standard" as there can be some left/right interference, left over momentum etc which isn't equalize to situation they measure and collect the data to create dynamic offset values.

If you get accurate value, good then. But why risking accuracy issue when you can buy power meter that doesn't have to do all these assumption to be accurate.

[TheRich]

They need dynamic compensation. To do so, they need to change offset values based on crank angle multiple time a circle.
And even so, it'll only accurate if your pedaling circle is "standard" as there can be some left/right interference, left over momentum etc which isn't equalize to situation they measure and collect the data to create dynamic offset values.

If you get accurate value, good then. But why risking accuracy issue when you can buy power meter that doesn't have to do all these assumption to be accurate.

There IS a way to check the accuracy of a power meter, but it doesn't involve using it as a power meter.

Apparently, almost all the crank based meters that GPL tested are just as wrong as Shimano, but somehow the problem is with Shimano.

Kinda baffled why a 1-2% is somehow critical. Oh, you were actually doing 300w and it read 306w, who cares? Worried about your TSS being off by 1 or 2 points? Is there some huge difference in effort that this critical error hides?

Edit: If you want a legitimate gripe, talk about the price.