Power Meter Brands

tunney

doozerie wrote: »

On another point, a lot of what I have read in magazines and online tends to suggest that the Powertap is a reliable and consistent power meter, and when people discuss potential inaccuracy they tend to focus on the likes of Stages which use extrapolation (or guesswork, depending on your point of view) to derive the power figure they display.

It's easy to conclude that there is a world of difference between Powertap and Stages, and while there are indeed clear distinctions in some respects, the boundaries can get very blurred over time. To take a specific example, if you replace the bearings in your Powertap yourself, then you won't have the means of confirming that it remains accurate afterwards. I replaced the bearings in my Powertap within a year, because the bearings were muck (or poorly installed at the factory, more likely), and while the power figures it has displayed since then seem to be in line with what it showed before, I've no idea whether it remains accurate, in reality. I could, of course, have had the bearings replaced by someone official like Paligap, but that's not cheap.

When you factor in the potential cost of maintaining a Powertap (I'm hoping it won't need new bearings every year, but who knows), and the potential loss of accuracy if you do the bearing replacement yourself, then Stages can start to look more appealing despite the possibility that it is not as accurate as Powertap from day one.

And now you get onto the whole next part

User verification of, and user setting, of calibration numbers.

Inquitus

I think the point is that the reviews, where tested against multiple PM's, have not demonstrated L/R imbalance or non linear imbalance that has significantly affected the results. In the testing that has been done, limited in scope thought it may be, the Stages has proved as accurate as more expensive dual leg solutions.

While I understand your concerns, there exists no evidence that they will impact the majority of users, granted there is also a dearth of testing.

doozerie

tunney wrote: »

When I was training properly I knew what a certain wattage should feel like and what heart rate I would typically be at. If for a given wattage my heart rate was elevated, or RPE off, then I knew that I had a problem. I was sick, overtrained or just having a bad day.

However if you cannot be sure of the power then those comparisons go out the window.

The comparisons could go out the window, yes, but not necessarily. In the absence of power data you'd have to use other metrics to make comparisons - some people used to consider average speed for a session to be a very useful metric, for example, whereas some would also consider this a meaningless metric.

Power data eliminates much of the subjective assessment and I think that's very useful, but some/many people trained very well before power meters existed. That ability to assess yourself without scientific data is not a skill that I possess, so the likes of me will always fare better with power data to help (assuming I use it well of course). And power data can arguably help any athlete raise their performance by some amount regardless of how skilled they already are at measuring their performance. But not having a power meter doesn't necessarily mean that your training is badly impaired. Not that I'm suggesting that that's what you are saying, but it's a view that can seem implied in discussions about power meters.

tunney wrote:

I really don't understand why someone would go one legged when for a small amount (relative) more you could get both legs.

I think it depends on your definition of "relative" in relation to cost. If you don't have the extra cash to spend on something more expensive than Stages then you're stumped, but even if you could find the extra cash you might decide that Stages is accurate "enough" for the money. People make choices like that all the time in relation to choice of bike, components, kit, etc., there may be more scientific evidence to support putting extra cash towards a more accurate power meter but that won't be compelling enough for everyone.

tunney

Last thing I'll say on this. Stages are not the first attempt at left only and there was peer reviewed research on a previous attempt, one that that took more samples per revolution than the Stages

http://www.humankinetics.com/acucustom/sitename/Documents/DocumentItem/10426.pdf

Results: The EP provided a significantly higher PO than the SRM and PT during the submaximal incrementaltest: The mean PO differences were +6.3% ± 2.5% and +11.1% ± 2.1%, respectively.
The difference was greater during field training sessions (+12.0% ± 5.7%
and +16.5% ± 5.9%) but lower during sprint tests (+1.6% ± 2.5% and +3.2% ± 2.7%). The reproducibility of the EP is lower than those of the SRM and PT (CV= 4.1% ± 1.8%, 1.9% ± 0.4%, and 2.1% ± 0.8%, respectively).
Conclusions: The EP power meter appears less valid and reliable than the SRM and PT systems.

I doubt you'll get a peer reviewed paper on Stages as the whole "measure the left and double it" done before.

Inquitus

tunney wrote: »

Last thing I'll say on this. Stages are not the first attempt at left only and there was peer reviewed research on a previous attempt, one that that took more samples per revolution than the Stages

http://www.humankinetics.com/acucustom/sitename/Documents/DocumentItem/10426.pdf



I doubt you'll get a peer reviewed paper on Stages as the whole "measure the left and double it" done before.

Based on a sample of 1 subject........

A regional-level male competitive cyclist (age 27 years, height 1.80 m, body mass
65 kg, maximal aerobic power 360 W) volunteered as the subject for this study.
Before testing and after having received full explanation concerning the nature
and the purpose of the study, the subject gave written informed consent. Before
participating, he underwent several habituation sessions to familiarize himself with
the testing procedure and material.

FrankGrimes

tunney wrote: »

For those reasons if the calibration of a power meter can not be user verified, if not set, that thats an issue for me.

Garmins are out as head units for me (they have an issue in and around recording of zero values when you stop pedalling, not an issue in a hill climb or straight TT but on a road race, training spin or crit it is)
And I want data to be consistent.

For me my LR balance changes over the course of a year, the more trained I am the less it is. It also changes year on year. I have the guts ten years of power data available in WKO. Each power meter has been professional calibrated and personally verified. I can accurately and confidently do historical analysis of data.

Interesting stuff. Does that mean you use the SRM Power Control head unit rather than a Garmin and it shows L/R power balance? How do you find that head unit overall? Does it have a barometric altimeter? Not sure I could do without the GPS functionality of the Garmin Edge 500, as I do like seeing what hills I've climbed, what the gradient is etc. But it seems the pros all use the SRM unit so I guess it must do some interesting stuff.

I've never done anything with my SRM other than calibrate on the Garmin device and the SRM back for new battery and calibration every 2 years. What's involved in the user calibration and did you find a big adjustment in your figures or only a small correction? I'm moving to Power2Max shortly, is recommended calibration approach there much different?

tunney

Inquitus wrote: »

Based on a sample of 1 subject........

My mistake. This paper is based on one subject and while it was done in a scientifically valid way the small sample set makes the research inferior to the test the DCRainmaker did that day on that ride and what the lad you know from the club did in the shed.


I fully retract my arguments and comments in the face of your fantastic argument and the overwhelming amount of evidence you have offered in support of it.

sconhome

Inquitus wrote: »

Based on a sample of 1 subject........

Would that not be the right thing to do? Same test subject conducting repeatable tests under the same conditions to eliminate as many variables as possible?

All testing sessions were performed by the same subject with the same road-racing bicycle (mass = 9 kg), which was equipped with clipless pedals. The mass of the system (subject + bicycle) contributes to the power required to ride on a treadmill at a given speed and gradient. A slight change in subject mass would have changed the PO required to ride on the treadmill, so every test day, the subject’s body mass was measured to avoid its influence on the PO ....

I know when I use two different systems the wattages will be slightly off from each other, one measures at the wheel, the other at the pedals but as long as I have a relative position to work from and my test protocol and conditions are similar I can track the increase / decrease of output through the year.

doozerie

tunney wrote: »

I fully retract my arguments ...

My reading of the debate so far is that you and most others are in agreement that Stages is not going to be as accurate as a power meter that (reliably) measures left and right independently (except for someone with consistent 50/50 balance, which I imagine is extremely rare even if they exist at all). For you that lack of accuracy is unacceptable, which is fair enough, for others it is acceptable, which is also fair enough.

An argument over whether the likes of Stages is accurate "enough" is never going to be won by either side. What would be far more interesting would be a discussion over exactly how accurate/inaccurate Stages is - some empirical data wouldn't settle the argument either (unless the figures were extreme) but it'd help make for a more reasoned debate and would help people define what "accurate enough" really means for them. I don't know if such data already exists and is publicly available, but some comparison between Stages and another power meter has already been mentioned and that could be a good start.

Inquitus

tunney wrote: »

My mistake. This paper is based on one subject and while it was done in a scientifically valid way the small sample set makes the research inferior to the test the DCRainmaker did that day on that ride and what the lad you know from the club did in the shed.


I fully retract my arguments and comments in the face of your fantastic argument and the overwhelming amount of evidence you have offered in support of it.

Any scientific study based on a sample of one isn't worth the paper it is written on. In addition to the fact its based on analysis of a different product using a different technology to measure power.

I did highlight in my post that the lack of research into this area is a concern, but a number of people have reviewed the data on the Stages versus SRMs / Powertaps etc. and none to date have come back with a result set that would cast any doubt on the Stages as a valid toll for Power based training.

Feel free to be as facetious as you like mind, I see you seem to struggle to remain civil at times in this debate.

CramCycle

tunney wrote: »

My mistake. This paper is based on one subject and while it was done in a scientifically valid way the small sample set makes the research inferior to the test the DCRainmaker did that day on that ride and what the lad you know from the club did in the shed.

TBF it does not make it any better than DCRainmaker either. The only benefit is that it was peer reviewed but that's not all it's cracked up to be in the modern publishing world either. (Caveat I haven't completely read through either so I could be talking out of my ass here).

Both studies have huge flaws, the number of participants, the number of trials, statistical relevance of some of the data. The best thing that summarises the paper is the conclusion stating "appears" as that all it is. Its a trend but it's far from statistically significant from my brief overview (the abstract).

It is a common issue with Sports Science studies where you often have only one participant.

I remember Kieron Collins doing a talk on it and it was an interesting discussion, talking about the issues with Sports Science and study of data. You could only take inferences out of the majority of papers, which are enough for a layman but not for most scientists but then you had such narrow parameters for acceptable subjects you could never get a large enough field of participants and had to settle for this.

fat bloke

What's the consensus on this new Garmin Vector S? Sounds like a really clever idea to apply some vaseline to power meter entrance. Buy one pedal and get going, and if you want to or feel you need to, get the other pedal.

1200 quid is a huge entry spend (at the end of the day, they're still only fcukin pedals!!! ). 700 or whatever they decide to be half, is a much more palatable , or at least much less unpalatable, price point.

Hmmzis

I think it's just a reaction from Garmin seeing how successful Stages are with their single leg version. It's more expensive than Stages but would suite if you have carbon cranks. On the other hand, if you think you would prefer if both legs are taken into account then a p2m is the way to go (or wait till 4iiii relese theirs, should be even cheaper than p2m for both legs).

harringtonp

Hmmzis wrote: »

I think it's just a reaction from Garmin seeing how successful Stages are with their single leg version. It's more expensive than Stages but would suite if you have carbon cranks. On the other hand, if you think you would prefer if both legs are taken into account then a p2m is the way to go (or wait till 4iiii relese theirs, should be even cheaper than p2m for both legs).

Yes cannot understand why people are talking about one leg not too easy too install/configure solutions when you have

http://www.power2max.de/europe/en/Produkt/bestsellers/power2max-fsa-gossamer-road/

EC1000

harringtonp wrote: »

Yes cannot understand why people are talking about one leg not too easy too install/configure solutions when you have

http://www.power2max.de/europe/en/Produkt/bestsellers/power2max-fsa-gossamer-road/

But if I go for a group spin today on my roadie and do intervals on my TT tomorrow - that's a bit impractical, right?

Garmin solution addresses that issue anyway - whatever about all the other issues.

mossym

EC1000 wrote: »

But if I go for a group spin today on my roadie and do intervals on my TT tomorrow - that's a bit impractical, right?

Garmin solution addresses that issue anyway - whatever about all the other issues.

why? can swap a crankset over in a couple of minutes? undo non drive side crank, remove, driveside and chain rings slide out, slide into other bike, and reattach non drive side crank

and i'd add, no messing about with the vector torque requirements, isn't it an awkward tool/method?

can't get why people think crankset PM's are difficult to move between bikes.

lennymc

if all your bikes run a compatible BB system then the crank option is probably easiest, but if you run different bb (press fit v cups etc) then crank isnt going to work unless you look at adaptors and stuff.

mossym

lennymc wrote: »

if all your bikes run a compatible BB system then the crank option is probably easiest, but if you ring different bb (press fit v cups etc) then crank isnt going to work unless you look at adaptors and stuff.

yeah, my cannondale tri bike is bb30, road bike is a 24mm, so installed a rotor bb30 to 24 adapter, namely this one,
http://www.rotorbikeusa.com/products/bb30-24_bottom_bracket.html

and it's been perfect.

fat bloke

mossym wrote: »

why? can swap a crankset over in a couple of minutes? undo non drive side crank, remove, driveside and chain rings slide out, slide into other bike, and reattach non drive side crank

and i'd add, no messing about with the vector torque requirements, isn't it an awkward tool/method?

can't get why people think crankset PM's are difficult to move between bikes.

If it works for you then fair play to you but when I'm going for a spin I find it taxing enough to remember where I left my helmet, find my other glove, pump the shaggin tires, make sure the garmin is charged and get a dump in before doing up my bib shorts and putting on pocket-stuffed jersey!

Throw in a crank change as well? A couple of minutes me hole, it'd take me that long to find the key for the shed to get the toolbox where I may or may not have left the crank removal tool.

mossym

fat bloke wrote: »

Throw in a crank change as well? A couple of minutes me hole, it'd take me that long to find the key for the shed to get the toolbox where I may or may not have left the crank removal tool.

sure you'll need to find the key to get the bike out of the shed anyway:)

you;d leverage that arguement against any of them though. if you;re going to be swapping pedals anyway, or cranks, then a crankset is no harder. if not comfortable doing that, then wheel based the next option, or stick the same pedals on all bikes and go brim brothers.

tunney

mossym wrote: »

sure you'll need to find the key to get the bike out of the shed anyway:)

you;d leverage that arguement against any of them though. if you;re going to be swapping pedals anyway, or cranks, then a crankset is no harder. if not comfortable doing that, then wheel based the next option, or stick the same pedals on all bikes and go brim brothers.

Lets put something in the pedals then?
Doesn't matter if it works, sure most people using it won't notice.

Kaisr Sose

fat bloke wrote: »

If it works for you then fair play to you but when I'm going for a spin I find it taxing enough to remember where I left my helmet, find my other glove, pump the shaggin tires, make sure the garmin is charged and get a dump in before doing up my bib shorts and putting on pocket-stuffed jersey!

Throw in a crank change as well? A couple of minutes me hole, it'd take me that long to find the key for the shed to get the toolbox where I may or may not have left the crank removal tool.

The left and right side argument again. :-)

Tip: Jersey easier to put on empty and then stuff with goodies.

As for the single side or both side power measurement discussion. The world is full of alternative solutions for the same thing. Often, there is no best or single method, but various options, each of which will be more or less appropriate to an individuals wants, needs, aims, budget, etc.
Its highly unlikely that this does not apply to Power Meters.

fat bloke

Kaisr Sose wrote: »

Tip: Jersey easier to put on empty and then stuff with goodies.

Indeed. But there is no more effective a laxative than a freshly zipped up jersey over bib shorts!

Re crank removal. I've conned myself with similar arguments wrt carbon wheels and tubs and specific brake pads "sure it only takes a second to swop out them out etc". I'm older and wiser now .

As for the 1 leg 2 leg argument. I would contend that it is far better for whole swathes of people to be able to (literally) get one leg on the training with power ladder due to a more affordable price point than to have the same swathes economically excluded. The option then to add the other leg at a later date is a practical and considerate and sensible one imo. And it's not one that will ever be available to the stages purchaser.

One leg is better than none though and every newcomer to the increasingly affordable power meter party should be welcomed.

tunney

fat bloke wrote: »

Indeed. But there is no more effective a laxative than a freshly zipped up jersey over bib shorts!

Re crank removal. I've conned myself with similar arguments wrt carbon wheels and tubs and specific brake pads "sure it only takes a second to swop out them out etc". I'm older and wiser now .

As for the 1 leg 2 leg argument. I would contend that it is far better for whole swathes of people to be able to (literally) get one leg on the training with power ladder due to a more affordable price point than to have the same swathes economically excluded. The option then to add the other leg at a later date is a practical and considerate and sensible one imo. And it's not one that will ever be available to the stages purchaser.

One leg is better than none though and every newcomer to the increasingly affordable power meter party should be welcomed.

Ah bless, looking forward to the Wicklow 200 next year?

fat bloke

tunney wrote: »

Ah bless, looking forward to the Wicklow 200 next year?

Why so because?

pprendeville

fat bloke wrote: »

Indeed. But there is no more effective a laxative than a freshly zipped up jersey over bib shorts!

Re crank removal. I've conned myself with similar arguments wrt carbon wheels and tubs and specific brake pads "sure it only takes a second to swop out them out etc". I'm older and wiser now .

As for the 1 leg 2 leg argument. I would contend that it is far better for whole swathes of people to be able to (literally) get one leg on the training with power ladder due to a more affordable price point than to have the same swathes economically excluded. The option then to add the other leg at a later date is a practical and considerate and sensible one imo. And it's not one that will ever be available to the stages purchaser.

One leg is better than none though and every newcomer to the increasingly affordable power meter party should be welcomed.

Hear hear. I thought it was just me that got excited bowels at the sight, no the smell of a pair of bib shorts.

Chips Lovell

Tunney banned for a week for repeated trollerization.

niceonetom

Have I slipped through a wormhole to 2008? I'm half expecting Kona to start throwing abuse...

...if this post makes any sense to you, you've been here too long. RUN! RUN YOU FOOLS!

fat bloke

Only professionals can have nice things

Ken1975

Folks need some help. Got stages ultegra 6800 and it calibrated fine on friday. Reading was 870. Forgot to zero it before a 4 hour spin on Sunday but also moved the bike from the shed to the kitchen where it stood for 20 mins so readings were off the wall.
This morning I zero'd outside before heading off and reading was 1194. I thought I may not havr left it outside long enough so carried on.
I left my bike in an underground carpark all day so temp should be fairly consistent. So calibrated before leaving this evening and reading was 1288.

Amy ideas how to get back to the original 870 reading.

Btw. Tried calibrating with no hrm on too. Same.

Cheers.
Ken.