The Problem with Power Meters

Power meters are fantastic pieces of equipment. However, there is one huge problem with them: each one gives a different reading, and some vary wildly in their accuracy. Can power meters actually be relied upon, or are they just expensive random number generators?

Welcome 0:00
Categories of Power Meters: Pedals, Cranks & Hubs 0:25
Power Pedals & Power Cranks 2:39
Accuracy of Power Meters 3:12
Does price affect accuracy? 5:03
Can you make a power meter more accurate? 5:28
How seriously do you take your training and data analysis? 6:39
What power meter would we suggest? 7:22
Conclusions - Tell us your experience in the comments 8:04

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[gcntech]

Do you own a power meter? Let us know in the comments 👇

[atsr_]

The biggest problem with a power meter is that it provides an exact measure of how much I suck as a cyclist

[stevereaburn]

Sim[ple : Don't buy a power meter until you've watched & understood the Shane Miller / GP Llama or DC Rainmaker reviews & analysis.

[martincburns]

Assioma Duo are the business. Super easy to swap between bikes if you're fortunate to have more than one. I use mine on the indoor trainer and outdoors for consistent readings. Accuracy is excellent.

[mikskuratmiks]

I picked up a used single sided crank power meter a few weeks ago - spent the winter months on the indoor trainer so I got used to seeing the numbers.
Very happy with the purchase so far. A positive surprise is that I am now much more tolerant of riding into a strong headwind as now I see that I truly can be putting in more effort even if it results in a slow speed. Like of course I realised that I *must* be putting in more power if my heart rate is going up but it's still nice to see it for sure.
So for me it has been worth it just to compare myself with myself, and makes you realise even more how useless comparing average speeds often is.

[SecwetGwiwer]

To sum up, Shimano power meters are notoriously inaccurate.

[FatboyAussie]

I’ve got the Assioma spindles. Completely changed my training. Love the data it gives me

[billeterk]

I thought my power meter pedals showed I produced more power changing from 172.5mm cranks to 170mm. They actually showed the importance of remembering to set the crank length to accurately measure torque. Sigh.

[zhuyufan]

I don't have a power meter nor do I planned to get one. I don't race but I do like to ride bikes, so I put the money of power meter into getting an entry level tubro trainner. By doing so, I can ride indoor when weather isn't good and get a stationary platform to dial in my riding position.

[swites]

I remember one day after a good month or two of training, I swapped my left sided stages pm off my training bike onto my race bike. I calibrated it and it gave a different number than usual, but I thought nothing of it. So I set off for my 3hr hilly loop and felt great. The ride was effortless and I was amazed at the power I was doing on the flats, and up the climbs. And thought "Man 300w's feels really easy up these climbs! I must have got fit all of a sudden. My training must have all come together and my body has finally adapted! Wow this is what it feels like one of those young A graders. This is great!" Then after a few hours I suddenly thought..."Hang on a minute. This can't be right, better stop and check the pm". And lo and behold I'd forgotten to tighten up the 2 pinch bolts on the crank! And it was only staying on with the help of it's shimano safety tag and dust cap! My short stint of being "a good cyclist" was over, and I rode home feeling rather silly at my usual 180 to 200w's :( lol

[MrLuigi-oigm]

I used Shane Miller/GP Llama's reviews, and replies he gave me to questions I asked him in the discussion section of his YouTube videos, to decide what power meter and indoor trainer to buy. Great guy and he's thorough, precise, and data driven. What more could you ask for? BTW, I have been very happy and impressed with the performance of the Wahoo KICKR V.6 trainer and Assioma Duo Shi power meter pedals he recommended.

[robertchung]

Nice balanced video (though you could've mentioned the expensive low-fidelity elephant in the room). Many riders claim that you don't need accuracy, all you need is consistency, but they don't know how or even bother to measure consistency. I think that the need for accuracy depends on what you're doing with the data, and there are widely different uses so there are widely different needs for accuracy and precision. Training FTP is one of the least demanding things you can do with a power meter, so a single-sided meter (or a dual-sided Shimano) are probably fine for that. Measuring CdA and Crr are *very* demanding uses, so you absolutely need high-fidelity data for that purpose.

[CS]

I’ve had the Faverro Assioma’s for 5 years now. They just work and are consistent. Fit and forget. Super easy to swap between bikes if you need to. Support from Faverro is excellent if you do ever have a problem.

[ime]

If you are using Shimano power meters, they are known to be very inaccurate on the right side

[klanyboyd]

The purchase of assioma duo was useful for me. because the distribution between the right and left legs turned out to be more important than the power itself. Now I distribute the load more evenly.

[PepeDalinShow]

Got myself a stages single-sided power meter 2 months ago. It totally change the game for me. I feel more motivated and consistent with my training because I can see how my capabilities on the bike improve.

[Ed.R]

Love how GCN has got so nerdy over power meters. Very well explained, and as far as i can tell, 100% accurate 👍

[garyhocking]

I have a 4iiii Precision 3+ single sided crankarm power meter. It has really helped with my outdoor training. It does read a little higher than my Wahoo trainer, but I don't mind as it is a consistent reading that I accounted for with power balancing..

[normanzielke]

Most useful way to compare efforts is to use power vs HR instead of power (or HR). There are many external factors such as weather (esp. heat), sleep and nutrition that can affect your readings, so having two values as well as a training diary makes it a lot easier to put the data into context.

[hugovangent]

Exactly my experience. I use an SRM pm on my road bike and a Quarq on my gravel bike. Quarq is >10W more optimistic