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What's the best power meter?

thomasmorristhomasmorris Posts: 373
edited August 2017 in Road general
Here's some good research on power meter accuracy and precision.

Original paper

A good selection of brands tested, although only a decent number of Stages, SRM, Quarq and PowerTap.

Stages comes out worst on both precision and accuracy. Coupled with the reliability issues and then left - right issues I'm not sure how anyone could still recommend this unit.

The Power2Max which is a forum favorite (and my PM) isn't fantastic, but only two units were tested. I'd like to see more units tested before I stop recommending this unit. It is famously reliable too, although not as cheap now given the euro - £ exchange rate.

It's not clear the exact models from each brand which are tested. However, SRM, Quarq, and PowerTap come out very well. As does Verve Infocrank but with just three units.

You'd have to say relative to cost (presuming this tested their cheaper PM options) Quarq and Powertap would be very good recommendations with choice between the two probably depending on your set up (powertap wheel easier to swap between bike, but do you want the hub on your race wheel rims or training wheels?).

Posts

  • Accuracy (as in true power output) believe it or not is not that important. It's the consistency in the figures. If a meter is regularly reading low compared to another it is not important so long as it constantly reads the same figures time and time again so you know any improvement is a fair reflection of your efforts.
  • redvisionredvision Posts: 2,515
    Accuracy (as in true power output) believe it or not is not that important. It's the consistency in the figures. If a meter is regularly reading low compared to another it is not important so long as it constantly reads the same figures time and time again so you know any improvement is a fair reflection of your efforts.

    This!
  • imposter2.0imposter2.0 Posts: 10,838
    As above - consistency/reliability over precision/accuracy
  • supermurph09supermurph09 Posts: 2,471
    Accuracy believe it or not is not that important. It's the consistency in the figures. If a meter is regularly reading low compared to another it is not important so long as it constantly reads the same figures time and time again so you know any improvement is a fair reflection of your efforts.

    I agree with this ^^^ but then again I have a Stages. As long as the reading is consistent then that is what matters most, having done lots of structured training I'm confident of knowing when something might be wrong so for me personally the Stages works. Having said that, part of me just wants to ditch power altogether.
  • Accuracy (as in true power output) believe it or not is not that important. It's the consistency in the figures. If a meter is regularly reading low compared to another it is not important so long as it constantly reads the same figures time and time again so you know any improvement is a fair reflection of your efforts.

    I agree, but some people due to specifications on their bikes are forced to use multiple brands / models.

    Or for convenience use two units from the same brand.

    You may want to know your X Model PM on bike A isn't reading different to X Model PM on Bike B.

    But yes, for the most part, precision is most important. But it seems there even stages falls down.
    The only unit that comes out badly in terms of average precision is the Stages power meter, which had a coefficient of variance of two per cent. Here, 300w might be 300w on one day and 294w or 306w the next day.

    The worst performer on the test was the Stages power meter. One unit showed a coefficient of variance of 6% – that means your 300w could be as much as 282-318w, which is well outside of what is useful when it comes to trying to ride to power or monitor your performance.
  • jgsijgsi Posts: 5,025
    Accuracy believe it or not is not that important. It's the consistency in the figures. If a meter is regularly reading low compared to another it is not important so long as it constantly reads the same figures time and time again so you know any improvement is a fair reflection of your efforts.

    I agree with this ^^^ but then again I have a Stages. As long as the reading is consistent then that is what matters most, having done lots of structured training I'm confident of knowing when something might be wrong so for me personally the Stages works. Having said that, part of me just wants to ditch power altogether.

    A like minded soul... same here... if it was not for Zwift...

    ( if I do go down the Eroica route, the last bleedin' thing I will have is a damn PM.)
  • okgookgo Posts: 4,368
    Love the people who constantly come out and defend their bad purchases with that line.

    Or how about this, for the same money get one that gives you the right numbers, time and time again?

    i've got 3 quarqs now, and I'm happy with them as a vendor, and I'm confident in the numbers in every sense.
    Blog on my first and now second season of proper riding/racing - www.firstseasonracing.com
  • ryan_w-2ryan_w-2 Posts: 1,160
    okgo wrote:
    Love the people who constantly come out and defend their bad purchases with that line.

    Or how about this, for the same money get one that gives you the right numbers, time and time again?

    i've got 3 quarqs now, and I'm happy with them as a vendor, and I'm confident in the numbers in every sense.

    Surely they're under-reading looking at your latest stats?...
    '17 Focus Mares Force 1 --- '19 Cervélo S5 Disc Di2

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  • twist83twist83 Posts: 761
    I have had a Stages, Rotor and Powertap. Honestly. I did not see much difference between them all. They all worked and were consistent enough for my level and needs.

    Unless you are Pro and every accurate Watt counts then I don't see the worry? Too many Faux Pro's.
  • slowbikeslowbike Posts: 8,476
    Hmm - I can't comment on the study as I'm not buying it just to read it. However, the article linked by the OP seems heavily anti-Stages biased - Stages being mentioned 10 times - all in the negative, powertap just 4 - SRM being the only one that tops Stages with 11 mentions - either positive or neutral.

    No attempt has been made to review the recording methods used, or the riders taking part.

    It's well known that Stages is left hand reading only (was - they're now selling the two sided version) - which has fundimental issues with leg imbalance. If I wanted to skew a power reading on Stages then I'd ride with one leg - simple. Even if I didn't want to skew it I'd have to make sure my perceived effort was balanced - not something you generally think about whilst riding.
    Looking at the article review - it's quite easy to look at the "Worst performer" stages - and chalk the entire discrepancy up to Rider leg imbalance - yet the review hasn't mentioned that posibility - is it mentioned in the original paper - I'd hope so.

    Personally - I'd go back to DCRainmaker's review
    https://www.dcrainmaker.com/2016/09/pow ... ition.html

    He's done his testing with between 4 and 7 power meters recording simultaneously onto a Wasp unit.

    I think this quote just about sums it all up:
    I think probably the biggest takeaway here is that no particular power meter is perfect. Anyone who says that there is, is sadly mistaken.
  • This is about the stupidest thing I've ever read. A freaking cord on a seatpost with a treadmill and some weights. Is this some grade-school science experiment? Where's Wil e Coyote and the Roadrunner?

    Amateur hour over here.

    Get back to me when you do it with precision calibrated instruments and precision machined testing rigs.

    "To do this, riders were placed on a treadmill set to a one per cent incline – but they were facing downhill (see figure one). A cord was attached to the seatpost, which in turn was linked to a weight to hold the rider in the same position on the treadmill.

    A second weight was added to the cord which, if the rider didn’t pedal, would pull them backwards up the slope. Because the mass of the additional weight was known, the researchers could then calculate power output, while also accounting for the loss of power through the drivetrain.

    This setup allowed the researchers to compare the average power as recorded on the various power meters to the true value. Each power meter was tested a number of times with a number of different riders."
  • twist83 wrote:
    I have had a Stages, Rotor and Powertap. Honestly. I did not see much difference between them all. They all worked and were consistent enough for my level and needs.

    Unless you are Pro and every accurate Watt counts then I don't see the worry? Too many Faux Pro's.


    I also wonder how many people know how to use it properly. It's not just having accurate numbers but knowing what they actually mean. If you have 3 and see very little difference that tells me you are looking beyond the basic raw figures and are being a bit more analytical which is what power meters are designed for.
  • supermurph09supermurph09 Posts: 2,471
    okgo wrote:
    Love the people who constantly come out and defend their bad purchases with that line.

    Or how about this, for the same money get one that gives you the right numbers, time and time again?

    i've got 3 quarqs now, and I'm happy with them as a vendor, and I'm confident in the numbers in every sense.

    Despite what I said, your point is valid, however at the time of purchase the money wasn't the same and if you can only afford one and need to swap it between bikes then the options were limited further.
  • okgookgo Posts: 4,368
    They were never limited, you fell for the marketing.

    Before I could afford to have 3 (about 5 years ago) I swapped it between bikes, it took about 90 seconds.

    I prefer to have accurate numbers, allows me to compare to my peers in certain events, ride on different bikes and see where the gap between my TT position and road for example is (impossible with two powermeters that have hugely different readings), also pretty sure having the wrong numbers would give you a totally wrong CdA figure for a TT position. Which would make sense as Aerocoach will give anyone with a stages a powertap to borrow for the session to make sure that the numbers stack up.

    It isn't about being a faux pro, its about buying a product that works, none of them are £50, so why accept one that is wrong, there is no point.
    Blog on my first and now second season of proper riding/racing - www.firstseasonracing.com
  • sungodsungod Posts: 12,202
    this has appeared in other places, based upon the reported details it appears to be a poorly controlled study

    maybe the original paper is being misrepresented, but it's paywalled, and based on what i've seen so far, they'd have to pay me to look at it
    my bike - faster than god's and twice as shiny
  • StillGoingStillGoing Posts: 5,153
    Very happy with P2M. Consistent and no need to calibrate repeatedly. Its also reasonably priced. I'd love a Quarq but the cost was prohibitive for me.
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
  • The one that compares me closest in W/Kg to Chris Froome? ;)
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  • milemuncher1milemuncher1 Posts: 1,472
    Power meters give you a number, with which to work. Whether the number supplied by a particular power meter is a true reflection of your actual output, is always going to be debatable, and difficult to ascertain, without cross referencing a standard, which is traceable to a recognised 'official' benchmark piece of equipment ( a calibrated certificated artifact), of which I'm not sure there are any. The most important thing is repeatability / stability / reliability of the equipment. The value for money of the equipment is important to me personally, as well. Through experience, I've found Stages to only be acceptable because of the relative low costs, they haven't been reliable or stable, IME. Garmin Vectors have been my favourites in the past, if for nothing else, than the flexibility of having a pedal based system, rather than crank based, the head units have been the biggest issue, with these though.
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