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"Best" power meter - money no object
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  Back when there were only a handful of players in the market, SRM used to be the 'gold standard'. Nowadays, I'm not so sure that's the case any more. It seems to me that the top offerings from many manufacturers rival the accuracy of the SRM, and most don't involve the hassle of having to send in your PM for service periodically. So, if you were to buy a power meter today and had an unlimited budget, what would you buy, and why? For argument's sake, let's assume that it will live on one bike permanently, so things like being able to easily swap from one bike to another aren't a factor.
Last edited by: el gato: Sep 12, 18 18:52
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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PT hub. That's what I have. It's been totally fit and forget. According to dcr, it's as accurate as anything out there. It's built into a training wheel that I cover for racing.

No muss, no fuss.
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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https://www.specialized.com/nz/en/s-works-power-cranksdual/p/134035
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Re: "Best" power meter - money no object [Tri2Bake] [ In reply to ]
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Don't want cranks. My cranks are 150mm selected as optimal for my fit. The sworks only go down to 170mm.

And $2k...for crank based power? Lots of cheaper options... What's special about s-works over one of the $500 options? I know the OP said cost is no object... But more money should still mean more <something>.
Last edited by: Tom_hampton: Sep 12, 18 19:48
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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I've been super happy with my Favero Assioma Duo's. Key point? They've been completely hassle free and 100% reliable. I've had them for about 9 months now and haven't had a single day that they wouldn't connect to my Bolt or Trainerroad on the PC. They've also never given me suspect power data despite the fact that I almost never calibrate them. Battery life is so long that its almost a problem, because I don't charge them regularly. In fact the only time they have failed on me was when I forgot to charge them before a race after like 3-4 weeks of not charging them. I actually bought them with the intention of switching them between my TT bike and road bike, but now I hardly ever do, as most of my training is on the TT bike anyways. However, it only takes <5 minutes to swap them if you need to.

Some people complain about the look of the pod, but its barely even noticeable once its on there.
Last edited by: Sikedsyko: Sep 12, 18 19:59
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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Quarq DZero.
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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It's no longer about the price - your main decision should be whether you want a hub based powermeter like powertap (always ride the same wheel, but free to choose pedals), or a crank based powermeter (choice in pedals and wheels) or pedals (choice in wheels only).

I have 3 powermeters - an old Powertap Pro+ hub, a Power2Max in a Rotor 3D crank, and a 3rd generation Stages (Left side only). They have all been very reliable, they give the same numbers, they're all set it and forget it systems. I think many powermeters give similar performance and are more than adequate as the training tools that we expect them to be.

Note I haven't tried pedal based powermeters because none of them use shimano cleats and I ride shimano tri and road shoes with shimano cleats on shimano pedals on all my bikes.
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Re: "Best" power meter - money no object [Benv] [ In reply to ]
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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el gato wrote:
So, if you were to buy a power meter today and had an unlimited budget, what would you buy, and why?

SRM with SRM computer.

It's the best.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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What does that mean? Is there a capability that influences one’s ability to train, race or analyze data?
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Don't want cranks. My cranks are 150mm selected as optimal for my fit. The sworks only go down to 170mm. //

Funny this is coming up right now, I just got my Infocranks in the mail for a new bike I'm building, 155's. For me that is my best option, they seem to be the class of crank based meters. It would be great to get the pedals I like with similar accuracy, but I think that is a few years down the road yet..
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Re: "Best" power meter - money no object [Benv] [ In reply to ]
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Sorry, I haven't investigated them thoroughly since they are too rich for me. I'm using an old Powertap SL+. But I'd guess SRMs still have better quality than the competition, and if anyone actually tested PMs for accuracy/precision they'd win. Lots of people who care about those features are still buying them even though they are 2-4x the price of other crank spider PMs. They can be easily calibrated also; I don't know which other PMs have that feature, but I think Quarqs do. BTW, new SRMs have rechargeable batteries.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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I am not ‘rich’, i am a data driven scientist so when someone makes blanket statements saying ‘A is better than B’ I just like to understand what relevant (to the intended purpose) data exists. I think there is lots of data showing there are many great powermeters but I have not seen data that confirms your claims regarding accuracy / precision or ‘being better’ in other ways.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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Re: "Best" power meter - money no object [Benv] [ In reply to ]
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Benv wrote:
I think there is lots of data showing there are many great powermeters

Is there really data supporting that claim? ;)

For most people "ballpark" precision is all they care about, and then features are more important. If you mean that there are a lot of PMs that work pretty well and give kinda similar numbers, then I'd agree with that.
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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I don't. He doesn't do aero testing with his PMs and he doesn't test them for accuracy/precision.
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Re: "Best" power meter - money no object [monty] [ In reply to ]
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monty wrote:
Funny this is coming up right now, I just got my Infocranks in the mail for a new bike I'm building, 155's. For me that is my best option, they seem to be the class of crank based meters. It would be great to get the pedals I like with similar accuracy, but I think that is a few years down the road yet..

Infocrank looks promising. Don't hold your breathe on the pedals though....
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:
I don't. He doesn't do aero testing with his PMs and he doesn't test them for accuracy/precision.

I don't understand what "aero testing" you mean.

He certainly does do accuracy and precision testing. You can argue the quality / validity of that testing, but you can't argue its existence.
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Field testing for CdA, where you are using the PM as a scientific instrument.

The only "accuracy testing" I've seen is when he compares the numbers from different PMs.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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+1 Quarq Dzero, been using it for a year without any problem, just bought another one for different crankset setup
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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SRM hands down. Set it and forget it. It works every single time.

The new SRM origin is rechargeable so no need to send in your pm to replace batteries.

get comfortable being uncomfortable
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Re: "Best" power meter - money no object [Benv] [ In reply to ]
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Benv wrote:
I have 3 powermeters - an old Powertap Pro+ hub, a Power2Max in a Rotor 3D crank, and a 3rd generation Stages (Left side only). They have all been very reliable, they give the same numbers

Do you have a frictionless drivetrain?

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Re: "Best" power meter - money no object [klehner] [ In reply to ]
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klehner wrote:
Benv wrote:

I have 3 powermeters - an old Powertap Pro+ hub, a Power2Max in a Rotor 3D crank, and a 3rd generation Stages (Left side only). They have all been very reliable, they give the same numbers


Do you have a frictionless drivetrain?


:-)

My PT G3 hub is about 4 watts off from my Quarq Elsa and Riken with a static torque test, which is expected since it is upstream from the weight on the pedals. As a recreational level cyclist, these PMs have been great for me, but I know that most of the serious guys that frequent Wattage seem to generally trust SRM more. If I were to go with the OP's question and money was no object than I would no doubt go with the SRM Orgin.
Last edited by: Felt_Rider: Sep 13, 18 3:23
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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if accuracy is the driving factor... an old dual reed switch wired SRM is still the best.
Infocrank is interesting, but using accelerometers to measure cadence is meh.

My Blog - http://leegoocrap.blogspot.com
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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In my opinion right now the Favero Assioma Duo's are the best PM on the market. For starters it is one of the most elegant solutions for swapping among bikes, I regularly am swapping between my Tri Bike, Road Bike and Gravel Bike. I have never had connection issues and have seen accurate results compared to the readings on my trainer. These things are also bomb proof, at first I was apprehensive putting them on my Gravel Bike but wanted to collect power data on a 4 hour gravel ride a few months back. That ride ended up turning into a mudfest due to heavy rain mid and I never had any issues only thing I needed to do was give them a nice cleaning afterwards to get the gunk out of the pedals.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:
Field testing for CdA, where you are using the PM as a scientific instrument.

The only "accuracy testing" I've seen is when he compares the numbers from different PMs.

As long as there are consistency to the readings why would accuracy testing be all that important?
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Re: "Best" power meter - money no object [mickison] [ In reply to ]
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There are a variety of reasons you might want accuracy as well as consistency. For example when you someday switch power meters, or when you have power meters on multiple bikes. Or if you race on Zwift and don't want to be that jerk who is zdoping. You specifically might not have a good reason to care (at the moment), but others do.
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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Unlimited budget? 2 SRMs, so that when one goes in for service I have a backup. What I recall reading somewhere, but could be mistaken, is that while other PM's are as good for steady state and most riding situations, SRM still handles peak sprinting forces and power better. Although sprint power and force isn't applicable for 99.9% of my riding, it would be nice to know that its there if I do decide to unleash my massive 20,000W sprint..

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Re: "Best" power meter - money no object [JasoninHalifax] [ In reply to ]
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Lord knows you wouldn't want your PM to only indicate 19,990. /pink
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Tom_hampton wrote:
Lord knows you wouldn't want your PM to only indicate 19,990. /pink

I would be really pissed if it showed a peak of 19,999.

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Re: "Best" power meter - money no object [mickison] [ In reply to ]
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mickison wrote:
rruff wrote:
Field testing for CdA, where you are using the PM as a scientific instrument.

The only "accuracy testing" I've seen is when he compares the numbers from different PMs.

As long as there are consistency to the readings why would accuracy testing be all that important?

1. If you ever switch pm's or use a smart trainer with a pm and your power numbers are now different, which pm do you believe? How do you now set your FTP or zones?
2. Aero testing - an inaccurate pm will lead to an inaccurate CdA
3. Analyzing data - whether you use the BBS tool or just want to compare w/kg to others on the same course. An inaccurate pm could lead you down the wrong path.

get comfortable being uncomfortable
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Re: "Best" power meter - money no object [stevej] [ In reply to ]
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I am with Steve on this one; money no object its a SRM hands down. I ride a quarq since money does matter.

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Re: "Best" power meter - money no object [jbank] [ In reply to ]
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jbank wrote:
There are a variety of reasons you might want accuracy as well as consistency. For example when you someday switch power meters, or when you have power meters on multiple bikes. Or if you race on Zwift and don't want to be that jerk who is zdoping. You specifically might not have a good reason to care (at the moment), but others do.

If I switch power meters, I retest my ftp. I used to attend a computrainer class. computrainer power numbers were always higher than my power meter. But the difference was consistence. Is there somebody out there that has done accuracy tests with most power meters and has charted the differences? so if ftp on power meter X is 256 then your ftp on power meter Y is 262. I don't think I've seen one but maybe it exists. If not, then you're back to if you switch power meters you need to retest. I can't say I've test a lot of power meters, but are there often such huge differences that you would cause a zdoping issue. I wouldn't think most differences would be greater than say 5-10 watts between power meters but I don't really have much experience with that.
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Re: "Best" power meter - money no object [mickison] [ In reply to ]
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You would think most wouldn't be different by more than 5-10 watts, but if you are including the power meters in various trainers, I think you would sadly be wrong. My stupid kickr was pretty wildly off as just one example. Fortunately had some quarqs that I trusted that helped identify just how inaccurate it was. Total pain to deal with its inaccuracy. It was consistent though.
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Re: "Best" power meter - money no object [mickison] [ In reply to ]
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To go back to the whole "just retest your FTP". Does your FTP never change? Do you test your FTP so frequently that you feel that you know it (for a given PM) precisely on any given day? If not, when you retest with your new PM, you will get a new FTP number, but you will lose the continuity in your training numbers. Was your recent training since your last FTP test effective? Maybe not a huge deal, but still pretty annoying if you are trying to monitor your fitness over a long period of time and trying to assess whether your training has been effective. Sure, this is probably not that big a deal if your PM is within 1-2%, but at 5% or 10% I would find that really annoying.

You can probably come up with some ways to handle that situation and work around the annoyance. I'm not saying that a consistent but inaccurate power meter is useless. But does accuracy add value? Yes, it does.
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Re: "Best" power meter - money no object [klehner] [ In reply to ]
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klehner wrote:
Benv wrote:

I have 3 powermeters - an old Powertap Pro+ hub, a Power2Max in a Rotor 3D crank, and a 3rd generation Stages (Left side only). They have all been very reliable, they give the same numbers


Do you have a frictionless drivetrain?
I do not have a frictionless drivetrain nor do my legs have the ability to apply power at a range of precision that is smaller than the differences between my power meters.
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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If only someone had done research on this very topic: OMG they did!!!!

Accuracy of Cycling Power Meters against a Mathematical Model of Treadmill Cycling
Authors Thomas Maier, Lucas Schmid, Beat Müller, Thomas Steiner, Jon Peter Wehrlin

http://dx.doi.org/10.1055/s-0043-102945 Published online: 8.5.2017 Int J Sports Med 2017; 38: 456–461

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Re: "Best" power meter - money no object [desert dude] [ In reply to ]
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how very Andrew Coggan of you... ;)

desert dude wrote:
If only someone had done research on this very topic: OMG they did!!!!

Accuracy of Cycling Power Meters against a Mathematical Model of Treadmill Cycling
Authors Thomas Maier, Lucas Schmid, Beat Müller, Thomas Steiner, Jon Peter Wehrlin

http://dx.doi.org/10.1055/s-0043-102945 Published online: 8.5.2017 Int J Sports Med 2017; 38: 456–461

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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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SRM easily. The latest has a replaceable battery to avoid sending it in, which I actually believe is not a good thing. Sending in SRMs every 3-5 years for a battery replacement allows SRM to do a full PMCS on it and I believe that extends the life, as I have 3 SRMs, aging from 10 years old, 7 years old and 1 year old.

PT/Quarq, etc are very good, for sure...



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Re: "Best" power meter - money no object [desert dude] [ In reply to ]
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desert dude wrote:
If only someone had done research on this very topic: OMG they did!!!!

Accuracy of Cycling Power Meters against a Mathematical Model of Treadmill Cycling
Authors Thomas Maier, Lucas Schmid, Beat Müller, Thomas Steiner, Jon Peter Wehrlin

http://dx.doi.org/10.1055/s-0043-102945 Published online: 8.5.2017 Int J Sports Med 2017; 38: 456–461


The "Limitations" section is pretty important, though. Temperature, vibration, etc.
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Re: "Best" power meter - money no object [desert dude] [ In reply to ]
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desert dude wrote:
If only someone had done research on this very topic: OMG they did!!!!


Accuracy of Cycling Power Meters against a Mathematical Model of Treadmill Cycling
Authors Thomas Maier, Lucas Schmid, Beat Müller, Thomas Steiner, Jon Peter Wehrlin

http://dx.doi.org/10.1055/s-0043-102945 Published online: 8.5.2017 Int J Sports Med 2017; 38: 456–461


Yup, I've read that before. Hence this this comment in my original post:

"It seems to me that the top offerings from many manufacturers rival the accuracy of the SRM"


Though it's hard to draw any real conclusions about some of the PM's in the report, like the Vector's, when they only tested one sample.


So, if we make the assumption that most of the 'premium' offerings (i,e, not those targeted for budget-conscious buyers like single-sided pedals) have similar accuracy, what differentiates the 'best' PM nowadays?
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Re: "Best" power meter - money no object [CPT Chaos] [ In reply to ]
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CPT Chaos wrote:
SRM easily. The latest has a replaceable battery to avoid sending it in, which I actually believe is not a good thing. Sending in SRMs every 3-5 years for a battery replacement allows SRM to do a full PMCS on it and I believe that extends the life, as I have 3 SRMs, aging from 10 years old, 7 years old and 1 year old.

PT/Quarq, etc are very good, for sure...
I prefer to charge/change the battery myself rather than sending it in. I'm in the process of changing the batteries in my SRM and noticed the service center in CO used EVE batteries on the last change rather than the original Eagle Picher. EVE stands for "Energy Very Endure" so I'm assuming they are a lower cost option from China. I don't know what PMCS is but I think it's positive you no longer have to send the new ones in for service.
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Tom_hampton wrote:
Not if you believe dcr :

https://www.dcrainmaker.com/...de-2017-edition.html

If you search you’ll find Coggan and dc rainmaker have gotten into arguments multiple times on here about the accuracy/precision/whatever about the testing the latter does. The gist of it is that there is a difference between power meters with SRM being the best but for 99% of riders it doesn’t matter.

Matt
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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el gato wrote:
Back when there were only a handful of players in the market, SRM used to be the 'gold standard'. Nowadays, I'm not so sure that's the case any more. It seems to me that the top offerings from many manufacturers rival the accuracy of the SRM, and most don't involve the hassle of having to send in your PM for service periodically. So, if you were to buy a power meter today and had an unlimited budget, what would you buy, and why? For argument's sake, let's assume that it will live on one bike permanently, so things like being able to easily swap from one bike to another aren't a factor.

Garmin and Pioneer will give you the most insight in to your pedal stroke, if you know what to do with that data those two are great. Stages dual leg are bullet proof.
I have PT wheel, Powertap P1 pedals, Garmin pedals, stages dual leg and stages single on my cross.
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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el gato wrote:
If we make the assumption that most of the 'premium' offerings (i,e, not those targeted for budget-conscious buyers like single-sided pedals) have similar accuracy, what differentiates the 'best' PM nowadays?
If you take accuracy off the table as a differentiator, which I agree is appropriate with the current offerings, then the differences become specific to each individual's preferences...

You already struck portability as a criterion, so that does not leave much as a differentiator.

Is it OK to assume "best" would be total power? If so, then that reduces choices to hub, crank, chainring, and dual-side pedal and crank arm offerings.

Is it OK to assume that "best" means accurate left/right power? Then, that reduces offerings to crank arms and pedals.

Is it OK to assume that "best" means pedal dynamics? Then, that reduces the offerings to pedals.

You eliminated budget-conscious, so does that filter Favero pedals?

By your filters and criteria, it seems like the best power meter is either PowerTap P1 or Garmin Vector 3.

OTOH, if your best diminishes pedal dynamics in favor of freedom to use any pedals, then Best would be Stages V3 dual sided or Shimano's new PM (when it is ready for prime time).

\Thread
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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Nobody has mentioned Power2Max yet. I have two - one for nearly three years, and the second for a bit over one year. Other than change the batteries once a year, I haven't had to do a single thing with them. They simply work. I had two Powertap wheels for eight years (race and training), and had a few issues over that time span with them. No experience with any other PM's, but highly recommend the P2M!


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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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Does SRM have active temperature compensation yet?
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Re: "Best" power meter - money no object [mickison] [ In reply to ]
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mickison wrote:
As long as there are consistency to the readings why would accuracy testing be all that important?

If a PM is consistent (precise) then accuracy is a trivial matter of calibration. In other words precision is the main problem.
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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If money is no object, the answer isn't one powermeter, but several. First, get a hub-based powertap for each rear wheel you will be using. Then, just so you can keep an eye on drivetrain friction, get an SRM or Power2max.

IMO, there is no substitute for a Powertap hub when it comes to field testing - particularly Chung testing. Crank and pedal based power are too loosely correlated with what actually gets to the wheel to be useful for many things.

If I had relied on my SRM alone, I would have blithely gone through life believing that Q-Rings and Osymmetric Rings were actually gaining me an extra 20 watts. The powertap set me straight on that. Looking back, the rolling resistance tests I did with the SRM are far more variable than the Powertap tests, which were dead-on repeatable.
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Re: "Best" power meter - money no object [desert dude] [ In reply to ]
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desert dude wrote:
If only someone had done research on this very topic: OMG they did!!!!

Accuracy of Cycling Power Meters against a Mathematical Model of Treadmill Cycling
Authors Thomas Maier, Lucas Schmid, Beat Müller, Thomas Steiner, Jon Peter Wehrlin


http://dx.doi.org/10.1055/s-0043-102945 Published online: 8.5.2017 Int J Sports Med 2017; 38: 456–461

From that article:


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Re: "Best" power meter - money no object [commendatore] [ In reply to ]
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This is the reason I switched to Quarq. That and the auto-zero issue with Garmin at the time.

For aero testing, it’s Powertap hubs for me.

Developing aero, fit and other fun stuff at Red is Faster
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Re: "Best" power meter - money no object [forshy0516] [ In reply to ]
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I'm also in the money no object camp and I agree.... big fan of my Assioma Duos. They've been accurate and reliable. One added advantage is if you travel to races, you can pack them in your carry on. If your bike gets lost and you need to buy/borrow a loaner, at least you'll have your PM. The one con I see is maybe the pedals aren't as aero as something like a Keo Blade or Speedplay Zero Aero, and the pods are kind of ugly.

I just added a DL Dura Ace Pioneer to Speedmax SLX because I didn't want to have to swap pedals between bikes, and on first ride had some drop-out issues. So we'll see that goes.... but leaning toward buying another set or two of Duos and just keeping a set of each of my bikes.

I've heard nothing but bad things about Stages and haven't tried. I had two sets of Vectors and both had the battery door issue and dropout problems. One set pooped out on me in a race.

I had a PT hub in my old training wheel set. It was bombproof and reliable, but it's kind of a fugly hubset.

I'd consider Quark if I was running SRAM, but my bikes are Di2 and Campy Mech.

I don't quite get the SRM love, frankly. I mean, sure it's the "gold standard" or whatever, but it's feature set is actually kind of lacking. The non-user-serviceable battery is a deal-killer for me. Presumably if money is no object, the value of your time is high. I don't have time to be changing and shipping around cranksets whenever I need a new battery.
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Re: "Best" power meter - money no object [SkippyKitten] [ In reply to ]
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Can someone please explain the advantage of PT hub in aero testing? It would seem this is actually a limiter if you want to test different wheelsets (rather than just position changes, accessories, etc.).
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Re: "Best" power meter - money no object [wintershade] [ In reply to ]
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wintershade wrote:
Can someone please explain the advantage of PT hub in aero testing? It would seem this is actually a limiter if you want to test different wheelsets (rather than just position changes, accessories, etc.).


You determine your aerodynamic drag (and your rolling resistance) by measuring your speed and power at the wheel (and then accounting for environmental factors -- grade, road surface, air density, wind, etc).

The problem with crank/chainring/pedal powermeters is they only give you an estimate of power at the wheel. Yeah, you can subtract 4-7 watts for drivetrain loss. But this number is not a constant. It's actually somewhat variable, being influenced by cadence, chainring/cog choice, etc. A Chung test, where you may change these factors systematically (because of the terrain), may therefore be systematically skewed.
Last edited by: jens: Sep 13, 18 13:17
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Re: "Best" power meter - money no object [jaretj] [ In reply to ]
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jaretj wrote:
Garmin does now:

https://buy.garmin.com/en-US/US/p/546361

That's for the Vector 2 & 2S, not for the Vector 3 & 3S......

-Brad Williams
Website | Twitter: @BW_Tri |Instagram: @BW_Tri | Strava | Co-Founder & Coach at: KIS Coaching
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Re: "Best" power meter - money no object [wintershade] [ In reply to ]
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Accuracy and precision are very good for starters with the G3. It’s also easy to install without needing calibration.

For aero testing where you’re interested in the energy delivered to the tyre rather than output by the rider, hub PM means you can, pretty much, ignore gearing and transmission losses.

Yes it limits rear wheel testing choices, but the impact of rear wheel on the rest of the system is extremely limited, and in the few cases* where we’ve been looking at rear wheel options, we could still use another PM, but then you have to factor in transmissison loss and gear changes in test. We do test that way, but hub PMs are preferred.

* front end changes are normally more significant. Most riders have a deep section rear and disc and use the disc unless it’s not allowed, or really hilly.

Developing aero, fit and other fun stuff at Red is Faster
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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SRM for reliability, accuracy and customer service. Nothing fancy - just German quality and engineering. Over the long term they end up being cheaper than all the others.
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Re: "Best" power meter - money no object [desert dude] [ In reply to ]
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desert dude wrote:
If only someone had done research on this very topic: OMG they did!!!!

Accuracy of Cycling Power Meters against a Mathematical Model of Treadmill Cycling
Authors Thomas Maier, Lucas Schmid, Beat Müller, Thomas Steiner, Jon Peter Wehrlin

http://dx.doi.org/10.1055/s-0043-102945 Published online: 8.5.2017 Int J Sports Med 2017; 38: 456–461
As a test of quasi steady state power accuracy it was an interesting exercise in attempting to provide an absolute standard as opposed to comparing one or more meters with one another. It's actually not an easy task to provide an absolute standard that at least bears some resemblance to they way people actually ride.

While the accuracy of quasi steady state power scenario is of interest to most in the world of triathlon, it's by no means an indicator of measurement accuracy in other riding scenarios, e.g. during accelerations and for peak power measurement. And this is still a limitation to consider as I'll explain further down.

As has been said already, it helps to understand the manner in which you plan to use the data in order to choose a meter appropriate to your needs (or whether indeed a power meter is needed at all).

Sometimes you don't know what you might like to do with the data, or whether such things as accurate peak power measurement matters. Even for a triathlete I think it does matter, especially if you are considering ways of applying the more recent power duration modelling since the peak power measurement does affect all the model's parameters.

And a final comment - it's not just the meter but also the devices used to capture and upload the data, the firmware/software doing the post processing of data and how they all interact with one another. Sometimes errors are not due to the meter itself.

http://www.cyclecoach.com
http://www.aerocoach.com.au
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Re: "Best" power meter - money no object [SkippyKitten] [ In reply to ]
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SkippyKitten wrote:
Accuracy and precision are very good for starters with the G3. It’s also easy to install without needing calibration.

For aero testing where you’re interested in the energy delivered to the tyre rather than output by the rider, hub PM means you can, pretty much, ignore gearing and transmission losses.

Yes it limits rear wheel testing choices, but the impact of rear wheel on the rest of the system is extremely limited, and in the few cases* where we’ve been looking at rear wheel options, we could still use another PM, but then you have to factor in transmissison loss and gear changes in test. We do test that way, but hub PMs are preferred.

* front end changes are normally more significant. Most riders have a deep section rear and disc and use the disc unless it’s not allowed, or really hilly.


Changing gear can affect the power accuracy of a Powertap as well (at a level that matters for aero testing). At least that's my experience when analysing such data from aero testing and is why when doing such testing we settle on staying in the same gear if we are using a Powertap.

Over the past decade or more of doing field testing indoors, I've never been let down by those with SRMs on their bikes. However I typically find with many other meters, while they still enable us to do good work for most aero testing stuff, they tend to provide data with a higher variability and so being able to nail down very small changes (e.g. an assessment of shoe covers) is harder or not possible or requires collection of so much data it's not cost effective for the time required.

http://www.cyclecoach.com
http://www.aerocoach.com.au
Last edited by: AlexS: Sep 13, 18 14:19
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Re: "Best" power meter - money no object [AlexS] [ In reply to ]
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I did say ‘pretty much’. :) I stick with one gear where possible and do track gears when data is available. It’s certainly good enough for shoe and shoe cover tests for example.

Developing aero, fit and other fun stuff at Red is Faster
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Re: "Best" power meter - money no object [SkippyKitten] [ In reply to ]
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I've been using a Quarq PM for years, and have no issues. I've sent it back for calibration once, when the numbers seemed to be off. That being said, I'll probably go with the new Look/SRM pedal for my next PM. This will give me the possibility to run Campy cranks with my Campy gruppo, and continue with my preferred pedal.
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Re: "Best" power meter - money no object [SkippyKitten] [ In reply to ]
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Skippykitten,
Do you have any quick recommendations for a value-minded wheel set to go with the G3 hub? I mean, like really on the cheap side. I'm still in my first year of cycling, so going super fancy would be overkill right now. The stock wheels that came with my bike are the Vuelta Zerolite Comp wheels and weight about 2050grams. I'm a "hobby" cyclist who wants to learn and do some at-home aero testing, so the hub is appealing.

I was considering ordering the DT Swiss R460 wheel set with G3 preinstalled since the set is rather inexpensive. Are there better options out there if I order everything separately and have the wheel built locally??


Thanks!
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Re: "Best" power meter - money no object [jens] [ In reply to ]
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jens wrote:
If money is no object, the answer isn't one powermeter, but several. First, get a hub-based powertap for each rear wheel you will be using. Then, just so you can keep an eye on drivetrain friction, get an SRM or Power2max.

IMO, there is no substitute for a Powertap hub when it comes to field testing - particularly Chung testing. Crank and pedal based power are too loosely correlated with what actually gets to the wheel to be useful for many things.

If I had relied on my SRM alone, I would have blithely gone through life believing that Q-Rings and Osymmetric Rings were actually gaining me an extra 20 watts. The powertap set me straight on that. Looking back, the rolling resistance tests I did with the SRM are far more variable than the Powertap tests, which were dead-on repeatable.

You shouldn't have needed to make any measurements to realize that non-round chainrings would alter the accuracy of the data.
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Re: "Best" power meter - money no object [Newduguy] [ In reply to ]
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Newduguy wrote:
Do you have any quick recommendations for a value-minded wheel set to go with the G3 hub? I mean, like really on the cheap side.

If racing then a cheap and deep Chinese rim with a cover would be ideal. For training really any decent rim and build is fine, and you can cover that also for races. $550 for the DT460 wheelset from Powertap looks real good to me!
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Re: "Best" power meter - money no object [SkippyKitten] [ In reply to ]
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SkippyKitten wrote:
I did say ‘pretty much’. :) I stick with one gear where possible and do track gears when data is available. It’s certainly good enough for shoe and shoe cover tests for example.
I never got data from Powertaps which enabled that level of precision with any reliability.

This is indoor track testing.

The torque zero would typically fluctuate such that you hit the limit with what was reliably testable. It was also my experience that some Powertaps were more susceptible to this than others. I've been through perhaps 30 PT hubs, and maybe one of them I could reliably test to this level, about half or so I could do aero work that was good enough for the session objectives, and the rest were fine as a power meter for general training but unsuitable for fine grade aero testing.

Prior to testing I always checked what meter we were using so I could set reasonable expectations on the typical precision limits. In some cases the rider themselves is the cause of most variability, especially if their bike fit is not so good and they are not rock solid stable on the bike.

http://www.cyclecoach.com
http://www.aerocoach.com.au
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:

If racing then a cheap and deep Chinese rim with a cover would be ideal. For training really any decent rim and build is fine, and you can cover that also for races. $550 for the DT460 wheelset from Powertap looks real good to me!

I have a dt460 with a pt hub that i built myself. Very happy with the 460...strong rim that has taken some serious hits in the last 24 months. I ran over a 1/2" bolt last year. Jarred me something fierce. It snake bit the tire on both sides and the tube. The rim was completely undamaged. Didn't ever loose true.

Earlier this summer, I hit a wheel sized pothole. ... Long story... I swerved and missed it with the front, but the rear dug in hard. Again bomb-proof.

I run it covered for racing.
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Re: "Best" power meter - money no object [AlexS] [ In reply to ]
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AlexS wrote:
I never got data from Powertaps which enabled that level of precision with any reliability. The torque zero would typically fluctuate such that you hit the limit with what was reliably testable.

I noticed that on rollers. <100W @>30mph ends up being very little torque at the hub. And one in-lb resolution isn't very fine.

Besides the SRM was there another PM you thought was better than a PT hub?
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Re: "Best" power meter - money no object [Andrew Coggan] [ In reply to ]
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Andrew Coggan wrote:
You shouldn't have needed to make any measurements to realize that non-round chainrings would alter the accuracy of the data.

Ouch. I'm a poet, not a scientist.

In my defense, I would point out that many others were misled by the bogus readings, including Bobby Julich and whoever was coaching him at the time. In fact the SRM guy I emailed about it insisted that the SRM was measuring the power accurately.
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Re: "Best" power meter - money no object [Sikedsyko] [ In reply to ]
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So I started looking into these after seeing a few ppl strongly recommended them here. I was getting all excited... They looked great... until I learned the battery isn't replaceable?

What have you heard is the expected life of the battery? Kinda sucks to think that in 3+ years you could have a $1200 paper weight just bc the battery is no longer!
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Re: "Best" power meter - money no object [JBell] [ In reply to ]
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JBell wrote:
So I started looking into these after seeing a few ppl strongly recommended them here. I was getting all excited... They looked great... until I learned the battery isn't replaceable?

What have you heard is the expected life of the battery? Kinda sucks to think that in 3+ years you could have a $1200 paper weight just bc the battery is no longer!
You'd need to ride a lot to wear out the battery in 3 yrs. It supposedly loses 20% of its capacity after 25,000 hrs. Still works just doesn't last quite as long between charges.
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Re: "Best" power meter - money no object [gregf83] [ In reply to ]
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Fair enough... That sounds pretty solid. I only picked 3 years bc the warranty is good for 2 ;)
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Re: "Best" power meter - money no object [ In reply to ]
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If I were interested in an SRM, but wanted 165mm cranks, are the SRM's with Rotor cranks my only option?
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:
And one in-lb resolution isn't very fine.

Hmmm. How old is your hub, and your head unit? I have 0.1 inch-lb resolution on mine.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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It's an SL+, with a Joule GPS+.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:
It's an SL+, with a Joule GPS+.

Hmmm. Isn't SL+ prior to the G3's? I think they've been reporting at 0.1 inch-lb resolution for a pretty long time.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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If you work through the math (taking into consideration typical wheel and crank RPM), the zero offset resolution of a PowerTap hub is only about 1/10th that of the average SRM crank.

IOW, a fair bit of error can still be hidden in the offset of a "properly zeroed" PowerTap.
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Re: "Best" power meter - money no object [Newduguy] [ In reply to ]
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I’ve used rims from Open Pros (28 2x) to Flo 90s. (Full carbon 24h 2x Sapim CX-Rays). Both of those build up very nicely. I’d not be averse to racing on the Flo. I’m not a big fan of covers for myself. I’d pair that with a 60-70mm front.

If you go for a deep section carbon rim, make sure it’s not a faired type because the larger flange on the G3 will mean that the spoke holes won’t line up with the fairing for you.

As noted, some of the prebuilt Powertap wheels are pretty good in their own right.

Developing aero, fit and other fun stuff at Red is Faster
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Re: "Best" power meter - money no object [Andrew Coggan] [ In reply to ]
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Andrew Coggan wrote:
jens wrote:

If money is no object, the answer isn't one powermeter, but several. First, get a hub-based powertap for each rear wheel you will be using. Then, just so you can keep an eye on drivetrain friction, get an SRM or Power2max.

IMO, there is no substitute for a Powertap hub when it comes to field testing - particularly Chung testing. Crank and pedal based power are too loosely correlated with what actually gets to the wheel to be useful for many things.

If I had relied on my SRM alone, I would have blithely gone through life believing that Q-Rings and Osymmetric Rings were actually gaining me an extra 20 watts. The powertap set me straight on that. Looking back, the rolling resistance tests I did with the SRM are far more variable than the Powertap tests, which were dead-on repeatable.


You shouldn't have needed to make any measurements to realize that non-round chainrings would alter the accuracy of the data.

I've often read that non round q rings would possibly decrease the accuracy of crank based pm readings. On the other hand P2M has stated various times that readings are not compromised by oval chain rings. My personal n+1 is: I'm riding a P2M with q-rings on a Tacx Neo. I'm not seeing differences of 20 watts between devices. Both power meters are rarely exactly identical in their reading, one is also somewhat slower than the other in picking up drastic changes, like at the start of a sprint. But using 30s rolling averages on a normal zwift training ride I rarely see differences exceeding 7 watts, (often they're closer) which is well within their respective 1% stated accuracy if you take into account a little bit of drive train loss.
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Re: "Best" power meter - money no object [surrey85] [ In reply to ]
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+1 for power2max. Great fit and forget PM. I have two now, one type s on my CX bike and NG on my tri bike. Both have worked brilliantly.
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Re: "Best" power meter - money no object [surrey85] [ In reply to ]
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P2M uses an accelerometer instead of a Reed switch to determine crank angular velocity, yes?

If they calculate power by multiplying the torque measured at points throughout the crank rotation by the near-instantaneous angular velocity measured at the same point, the data will be noisier, but use of non-round rings should not be an issue.

OTOH, if they simply use the accelerometer data to determine the overall average crank angular velocity (as with a reed switch) then non-round rings will inflate the power measurements, regardless of anything the company might claim.

Alex Simmons would likely know which of these two possibilities is correct. Hopefully he will see this and chime in.
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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el gato wrote:
If I were interested in an SRM, but wanted 165mm cranks, are the SRM's with Rotor cranks my only option?

I think so, unfortunately. I believe I purchased the last DA9000 SRM pm in 165mm that the CO folks had, and that was almost a year ago.
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Re: "Best" power meter - money no object [Bdaghisallo] [ In reply to ]
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With the switch to Look crank arms on the origin, Look only has their adjustable crank arms down to 170mm (ZED2 crankset).

https://www.lookcycle.com/en/components-bicycles/

While the ability to adjust crank length is awesome, SRM has now made themselves dependent on Look. Honestly, they should have just kept the DA9000 SRM along with the new Origin.

get comfortable being uncomfortable
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Re: "Best" power meter - money no object [stevej] [ In reply to ]
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stevej wrote:
With the switch to Look crank arms on the origin, Look only has their adjustable crank arms down to 170mm (ZED2 crankset).

https://www.lookcycle.com/en/components-bicycles/

While the ability to adjust crank length is awesome, SRM has now made themselves dependent on Look. Honestly, they should have just kept the DA9000 SRM along with the new Origin.

I don't know that SRM had that option. With Shimano introducing their own powermeter, and many of their Protour teams using the SRM DA PM, I don't Shimano were too excited about continuing to produce bespoke cranks for a competitor that might slow the adoption of their own powermeter.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
Hmmm. Isn't SL+ prior to the G3's? I think they've been reporting at 0.1 inch-lb resolution for a pretty long time.

Yes, circa 2010 or so. If you put it in testing or calibration mode and display torque you get a decimal like 508.3? I only get whole numbers of in-lb.

The .csv export is in N-m, but it appears the data is converted from 1 in-lb steps. .11, .225, .335, etc. are the lowest values.
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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I didn't read all the comments but as of late or the updates the Garmin V3 pedals have been flat out amazing for me. They also read within 1-2 watts of my Kickr on any 1hr ride which is great to me. I think they are a fantastic choice "now" and should be considered if you want pedal based.


I think a year or so from now the SRM pedals are going to be killing it - but to me the V3 are the choice with a close following of the Assioma. Garmin really shot themselves in the foot on this deal but I think will make it after everyone forgets haha

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Re: "Best" power meter - money no object [Andrew Coggan] [ In reply to ]
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Andrew Coggan wrote:
P2M uses an accelerometer instead of a Reed switch to determine crank angular velocity, yes?

If they calculate power by multiplying the torque measured at points throughout the crank rotation by the near-instantaneous angular velocity measured at the same point, the data will be noisier, but use of non-round rings should not be an issue.

OTOH, if they simply use the accelerometer data to determine the overall average crank angular velocity (as with a reed switch) then non-round rings will inflate the power measurements, regardless of anything the company might claim.

Alex Simmons would likely know which of these two possibilities is correct. Hopefully he will see this and chime in.
I don't know the real answer.

Many moons ago P2M made a claim about measuring angular velocity data (I'm not going to search for the links to the reference conversation though) but when asked to supply data showing angular velocity measured with a frequency greater than once per crank revolution, they wouldn't.

What I don't know is if that also means they couldn't.

That did not leave me overly convinced about their claim.

I suppose the only way we'll know is for someone with sufficient experimental rigour to perform some tests.

http://www.cyclecoach.com
http://www.aerocoach.com.au
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Re: "Best" power meter - money no object [AlexS] [ In reply to ]
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I have a P2M NGEco power meter, sufficient experimental rigor (I'm a practicing engineer), and some time. Say I wanted to have fun on a Saturday morning and run some tests....

What would I do and what data should I collect? Or is this more of a complex exercise that needs a lot of experience?

I see that P2M does't have a high frequency mode in their app. Is this something that would be required?
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Re: "Best" power meter - money no object [Newduguy] [ In reply to ]
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Newduguy wrote:
I have a P2M NGEco power meter, sufficient experimental rigor (I'm a practicing engineer), and some time. Say I wanted to have fun on a Saturday morning and run some tests....

What would I do and what data should I collect? Or is this more of a complex exercise that needs a lot of experience?

I see that P2M does't have a high frequency mode in their app. Is this something that would be required?
Provided you can do a slope calibration test for each set of chainrings after fitting them and have a way to reliably compare with power delivered to the rear wheel (e.g. a reliable Powertap wheel), that would be enough for an initial set of tests.

http://www.cyclecoach.com
http://www.aerocoach.com.au
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Re: "Best" power meter - money no object [wintershade] [ In reply to ]
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wintershade wrote:
I don't quite get the SRM love, frankly. I mean, sure it's the "gold standard" or whatever, but it's feature set is actually kind of lacking. The non-user-serviceable battery is a deal-killer for me. Presumably if money is no object, the value of your time is high. I don't have time to be changing and shipping around cranksets whenever I need a new battery.

Have you owned one? Serious question.

Battery life of road units is up to 3,000 hours. If you train 20 hours per week, every week of the year, that's 3 years. Most people (a) don't train that much per week (esp on a single bike) and (b) don't train that much year-round. 5 years of battery life is not unusual.

Sending a power meter (ANY power meter) in for a check-up every 5 years is not a bad thing to verify it is to-spec.

Then again, you rarely see meters of many brands that will actually work after 5 years -- a 5-year old SRM still has value on the used market; that's not the case for most other products. That is sad to me as none of these products are inexpensive.

(I own, service and sell a variety of meters, including SRMs. Personally I have several of both road and MTB units in active rotation, going back 7 years. They just work*, which has extreme value to a busy person.)

* - Any electronic device on a bike exposed to the elements can have a problem; SRMs tend to have fewer than most other brands, but they are not completely immune.
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Re: "Best" power meter - money no object [CPT Chaos] [ In reply to ]
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CPT Chaos wrote:
SRM easily. The latest has a replaceable battery to avoid sending it in, which I actually believe is not a good thing. Sending in SRMs every 3-5 years for a battery replacement allows SRM to do a full PMCS on it and I believe that extends the life, as I have 3 SRMs, aging from 10 years old, 7 years old and 1 year old.

I think you mean "rechargeable", not "replaceable", correct?

The latest (Origin) SRM power meter has a rechargeable battery *as an option*.

Some customers insist they want this, but I personally do not use it. Why? The discharge properties of rechargeable batteries are different than regular cells, and the latter tend to retain more consistent voltage over their usable life, which affects power readings.

Unless someone *really* has a special use for it, I advise them to get the non-rechargeable versions.

As you said, sending the meter in once every 3-5 years is actually valuable, though we would all prefer to never send any device in for servicing.
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Re: "Best" power meter - money no object [commendatore] [ In reply to ]
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commendatore wrote:
Does SRM have active temperature compensation yet?


"Yet" would imply that it is necessary.

Their hardware design makes their meter immune to temperature swings. The delta between a morning temperature in my garage vs peak ride temperature can be 50F, yet the zero offset on my SRMs changes <1% (=~3w @ 90rpm) at any point in a ride. I've tested and observed other meters to vary up to 10% for the same conditions -- and even in temperature-controlled environments!

(Yes, I was SHOCKED when I did the detailed testing.)

Software temperature compensation was sold as a feature, but it is using software to solve a problem that did not have to exist in hardware.
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Re: "Best" power meter - money no object [tetonrider] [ In reply to ]
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tetonrider wrote:

The latest (Origin) SRM power meter has a rechargeable battery *as an option*.

Some customers insist they want this, but I personally do not use it. Why? The discharge properties of rechargeable batteries are different than regular cells, and the latter tend to retain more consistent voltage over their usable life, which affects power readings.

Unless someone *really* has a special use for it, I advise them to get the non-rechargeable versions.

I'm no engineer but to me as a layman it would seem like a pretty bad design by SRM if the smallish powerdrop you see on a typical discharge curve of rechargable batteries at very low currents would actually significantly affect power readings. But then most discharge curves you find online seem to indicate that many rechargeable batteries actually have less vdrop than button cells or typical alkaline batteries.

Getting your unit looked at and checked by the manufacturer at certain intervals seems great but having to send it in for exchange of battery seems ridiculous.
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Re: "Best" power meter - money no object [surrey85] [ In reply to ]
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surrey85 wrote:
tetonrider wrote:


The latest (Origin) SRM power meter has a rechargeable battery *as an option*.

Some customers insist they want this, but I personally do not use it. Why? The discharge properties of rechargeable batteries are different than regular cells, and the latter tend to retain more consistent voltage over their usable life, which affects power readings.

Unless someone *really* has a special use for it, I advise them to get the non-rechargeable versions.


I'm no engineer but to me as a layman it would seem like a pretty bad design by SRM if the smallish powerdrop you see on a typical discharge curve of rechargable batteries at very low currents would actually significantly affect power readings. But then most discharge curves you find online seem to indicate that many rechargeable batteries actually have less vdrop than button cells or typical alkaline batteries.

Getting your unit looked at and checked by the manufacturer at certain intervals seems great but having to send it in for exchange of battery seems ridiculous.

I could be mistaken about the voltage drop -- it may be another property of the battery -- but suffice to say that power meters are quite sensitive to battery. anyone that has owned a Quarq and seen even the slight difference in a CR2032 cell (maybe it's an old CR2032 or a different brand) can attest to this.

that said, a "user replaceable battery" was touted as a feature way back when SRMs had battery life of ~1 year. yes, sending in a unit annually was a hassle. doesn't a battery you can replace at home sound amazing?

HOWEVER... how many owners of Quarq units or Stages or any other meter with a "user replaceable battery" have discovered that the battery cover is a common failure point for the ingress of water? almost every user i've known of those meters (myself included) has had one or more fail that way. SRMs *tend* to perform materially better in inclement weather for the very reason that the batteries are NOT easily replaceable by the end user*.

with up to 3,000h of battery life, i'd wager that having to send it in is not really an issue any longer and is only held up by people who want to find a reason not to get an SRM.

and that's fine -- all power meters involve trade-offs.

i'd argue that a non-user-replaceable battery is a FEATURE, not a bug. each to his own, of course.
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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el gato wrote:
If I were interested in an SRM, but wanted 165mm cranks, are the SRM's with Rotor cranks my only option?


Was just reading through this thread and saw your question again. SRM has recently announced that they will be offering an aluminum Origin crankset for their powermeter and this will be available with both 160mm and 165mm arms.


http://store.srm.de/origin-powermeter.html
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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IQ2

_________________________
27 years and counting
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Re: "Best" power meter - money no object [el gato] [ In reply to ]
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el gato wrote:
Back when there were only a handful of players in the market, SRM used to be the 'gold standard'. Nowadays, I'm not so sure that's the case any more. It seems to me that the top offerings from many manufacturers rival the accuracy of the SRM, and most don't involve the hassle of having to send in your PM for service periodically. So, if you were to buy a power meter today and had an unlimited budget, what would you buy, and why? For argument's sake, let's assume that it will live on one bike permanently, so things like being able to easily swap from one bike to another aren't a factor.

I’m going to say the Verve InfoCrank and then do some carbon work to make it aero. SRM used to be the gold standard but I find it to be much hassle than its worth at least once a year when I have to send it back for battery issues.

I’ve also heard that Rotor has something new in the works so I’ll hold further judgement until then.
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Re: "Best" power meter - money no object [Ohio_Roadie] [ In reply to ]
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Ohio_Roadie wrote:
I’m going to say the Verve InfoCrank and then do some carbon work to make it aero.

You sure that won't affect the readings? Seems like anything that would effect the stiffness would be bad.
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Re: "Best" power meter - money no object [Ohio_Roadie] [ In reply to ]
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Ohio_Roadie wrote:
SRM used to be the gold standard but I find it to be much hassle than its worth at least once a year when I have to send it back for battery issues.

That hasn't been the case in quite a while. SRM has been producing powermeters with 2K hours plus battery life for a number of years now.
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Re: "Best" power meter - money no object [Bdaghisallo] [ In reply to ]
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SRM also offers rechargeable powermeters.
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Re: "Best" power meter - money no object [Ohio_Roadie] [ In reply to ]
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Ohio_Roadie wrote:
el gato wrote:
Back when there were only a handful of players in the market, SRM used to be the 'gold standard'. Nowadays, I'm not so sure that's the case any more. It seems to me that the top offerings from many manufacturers rival the accuracy of the SRM, and most don't involve the hassle of having to send in your PM for service periodically. So, if you were to buy a power meter today and had an unlimited budget, what would you buy, and why? For argument's sake, let's assume that it will live on one bike permanently, so things like being able to easily swap from one bike to another aren't a factor.


I’m going to say the Verve InfoCrank and then do some carbon work to make it aero. SRM used to be the gold standard but I find it to be much hassle than its worth at least once a year when I have to send it back for battery issues.

I’ve also heard that Rotor has something new in the works so I’ll hold further judgement until then.

Have been quite impressed with the InfoCrank recently installed on my wife's Premier Tactical so far. Just wish it looked sexier.

I'm racing 2019 IM Arizona as part of Team Smile Train. Will I implode? Will I finish strong? Donate to find out more!
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Re: "Best" power meter - money no object [jkhayc] [ In reply to ]
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I've had stages, 4iii, powertap hubs and currently the favero assioma dual sided pedals. I love the pedals- they are so easy to swap between multiple bikes, and I've had zero issues in 600 plus hours of usage. 4iii was solid too.

That said, if I had a mandate to spend someone else's money and had to buy a new power meter for MSRP, I'd get the Verve Infocrank. Probably the most proven high level of accuracy out there, but you do pay $$ for it.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:
RChung wrote:
Hmmm. Isn't SL+ prior to the G3's? I think they've been reporting at 0.1 inch-lb resolution for a pretty long time.


Yes, circa 2010 or so. If you put it in testing or calibration mode and display torque you get a decimal like 508.3? I only get whole numbers of in-lb.

Sorry, I just saw this. Yup. Torque on my G3 is reported in 0.1 inch-lb resolution.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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That sounds like a good reason to get a new hub. 1 in-lb is pretty course sometimes.
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Tom_hampton wrote:
PT hub. That's what I have. It's been totally fit and forget. According to dcr, it's as accurate as anything out there. It's built into a training wheel that I cover for racing.

No muss, no fuss.

How much of a hassle is it putting the cover on and off? I've been very satisfied with the PT Elite+ wheelset I bought second-hand for my road bike, and was thinking about going with a G3/R-460 rear wheel for the tri bike with an AeroJacket for racing.

"They're made of latex, not nitroglycerin"
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
rruff wrote:
RChung wrote:
Hmmm. Isn't SL+ prior to the G3's? I think they've been reporting at 0.1 inch-lb resolution for a pretty long time.


Yes, circa 2010 or so. If you put it in testing or calibration mode and display torque you get a decimal like 508.3? I only get whole numbers of in-lb.


Sorry, I just saw this. Yup. Torque on my G3 is reported in 0.1 inch-lb resolution.

How do you see that? I have a Powertap G3 Track hub and the offset value I get is usually "10" or "11".
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Re: "Best" power meter - money no object [ In reply to ]
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I like the Quarqs and SRMs with someone else's money
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Re: "Best" power meter - money no object [gary p] [ In reply to ]
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Mine is a DIY cover using MonoKote. I leave it on year round. Can't speak to the Aerojacket. But, I think there are tons of other threads that talk about it.
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Tom_hampton wrote:
PT hub. That's what I have. It's been totally fit and forget. According to dcr, it's as accurate as anything out there. It's built into a training wheel that I cover for racing.

No muss, no fuss.

Agreed. It's the most "plug and play" of all the PMs in my experience.

And, since "money is no object", just buy a PT hub for every wheel you ever get for the bike...and you'll still have less total outlay than many of the other PMs mentioned here :-)



http://bikeblather.blogspot.com/
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Re: "Best" power meter - money no object [MTM] [ In reply to ]
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MTM wrote:
RChung wrote:

Sorry, I just saw this. Yup. Torque on my G3 is reported in 0.1 inch-lb resolution.


How do you see that? I have a Powertap G3 Track hub and the offset value I get is usually "10" or "11".

The offset value is different on my head unit than the torque value itself. Didn't PT change the offset value from a number close to 512 to one close to 0?
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
MTM wrote:
RChung wrote:


Sorry, I just saw this. Yup. Torque on my G3 is reported in 0.1 inch-lb resolution.


How do you see that? I have a Powertap G3 Track hub and the offset value I get is usually "10" or "11".


The offset value is different on my head unit than the torque value itself. Didn't PT change the offset value from a number close to 512 to one close to 0?

I think they did, but I'm not that versed in Powertap offset values. I was wondering what one unit in the offset (as showed on my Garmin) corresponds to.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
MTM wrote:
RChung wrote:


Sorry, I just saw this. Yup. Torque on my G3 is reported in 0.1 inch-lb resolution.


How do you see that? I have a Powertap G3 Track hub and the offset value I get is usually "10" or "11".


The offset value is different on my head unit than the torque value itself. Didn't PT change the offset value from a number close to 512 to one close to 0?

Yes....this was a blog post I did back in 2016.

Mine is usually -12 consistently and I have done a static torque test to verify the G3. Based on what I posted it supposedly be -30 to +30 from a PowerTap blog post.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
MTM wrote:
RChung wrote:


Sorry, I just saw this. Yup. Torque on my G3 is reported in 0.1 inch-lb resolution.


How do you see that? I have a Powertap G3 Track hub and the offset value I get is usually "10" or "11".


The offset value is different on my head unit than the torque value itself. Didn't PT change the offset value from a number close to 512 to one close to 0?
I think my Garmin uses 1in-lb resolution so perhaps you need the cycleops or a different head unit to get .1 resolution.
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Re: "Best" power meter - money no object [gregf83] [ In reply to ]
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gregf83 wrote:
I think my Garmin uses 1in-lb resolution so perhaps you need the cycleops or a different head unit to get .1 resolution.
That would suck.
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Re: "Best" power meter - money no object [MTM] [ In reply to ]
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MTM wrote:
I think they did, but I'm not that versed in Powertap offset values. I was wondering what one unit in the offset (as showed on my Garmin) corresponds to.
Ah, if I've read the PT site properly (and that's not a 100% sure thing) they switched from displaying torque and offset from inch-pounds to Nm. With the current firmware, one unit is .1 Nm, so an offset value of 10 or 11 means an offset of 1.0 or 1.1 Nm.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
gregf83 wrote:
I think my Garmin uses 1in-lb resolution so perhaps you need the cycleops or a different head unit to get .1 resolution.

That would suck.
I mis-remembered. The zero offset value is an integer but the torque is displayed to two decimal places. Likely Nm.
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Re: "Best" power meter - money no object [tfleeger] [ In reply to ]
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tfleeger wrote:
Quarq DZero.

I have this meter on all my bikes (cross, road, mtb) for consistency but I've had zero problems with them in a couple of years of use.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
MTM wrote:

I think they did, but I'm not that versed in Powertap offset values. I was wondering what one unit in the offset (as showed on my Garmin) corresponds to.

Ah, if I've read the PT site properly (and that's not a 100% sure thing) they switched from displaying torque and offset from inch-pounds to Nm. With the current firmware, one unit is .1 Nm, so an offset value of 10 or 11 means an offset of 1.0 or 1.1 Nm.

Thanks, hopefully that's correct as that would be decent resolution. 0.1 Nm is around 1W at 95rpm if my quick math is correct.
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Re: "Best" power meter - money no object [jhammond] [ In reply to ]
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jhammond wrote:
tfleeger wrote:
Quarq DZero.


I have this meter on all my bikes (cross, road, mtb) for consistency but I've had zero problems with them in a couple of years of use.

Be aware that just because you have the same brand/model of powermeter, they are definitely not necessarily reading the same. I've had two Quarqs (different models, though) and we have a handful or so of riders on my team with Quarq DZeros. Haven't rigorously tested them against each other, but from riding with my team in the mountains I am quite certain some of them are several percentages different to others. Of course, for some a 3-4% difference doesn't matter - for me it does.
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Re: "Best" power meter - money no object [AlexS] [ In reply to ]
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I've got a P2M (S Type) with Rotor Q rings and a Powertap G3 - I've never done any specific testing in relation to the oval rings and have never run the P2M with round rings as it came with the ovals second hand.
I have run them at the same time and they tracked pretty much exactly over a 30min ride with varying power between 0 & 500W. The P2M was slightly higher overall (@2%) on average but I would expect that given it is further up the drivetrain and that's also within the accuracy level of the two meters combined.

If the oval rings were inflating the power what kind of variance would you expect to see (a previous poster mentioned 20W) or is it more complicated than that and my N=1 doesn't prove anything either way?

Ps. I bought them both second hand, used them year round in all weather (more so the Powertap) and neither has ever missed a beat so would happily recommend either.
Last edited by: JaRok2300: Mar 8, 19 7:02
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Re: "Best" power meter - money no object [JaRok2300] [ In reply to ]
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It depends on how oval the rings are but years ago one of the oval manufacturers claimed a 3% difference in power by using their rings. So one of the guys on the old Wattage List had an SRM, a PT hub, oval and round chain rings and, most importantly, a high boredom threshold. He did a static torque test on the PT and the SRM with round rings, then collected data from both. Then he swapped to the oval rings, did a static torque test, and repeated the data collection. Compared to the PT, the SRM/oval ring reading was -- drum roll -- about 3% higher than the reading from the SRM/round ring.
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Tom_hampton wrote:
Mine is a DIY cover using MonoKote.

Is there a report on how you did it? Would love to see it.
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Re: "Best" power meter - money no object [MTM] [ In reply to ]
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MTM wrote:
I think they did, but I'm not that versed in Powertap offset values. I was wondering what one unit in the offset (as showed on my Garmin) corresponds to.


Looks like N-m if using Ant+. https://www.powertap.com/...tes-to-offset-values
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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I followed someone else's report on here for how they did it.

https://forum.slowtwitch.com/...ost=5539564#p5539564

The stuff is very tough. It's surprisingly hard to tear or puncture. So, I just leave it on year round. It's easy to fix if it does get a hole.
Small punctures can be repaired with electrical or clear packing tape. Larger tears can be patched with a piece of monokote.

My rear wheel is a dt swiss r460. I think that's about the shortest profile that will have enough surface area to glue the film too.

A roll of monokote is about $20... And is enough for 1 wheel, plus some leftover for patching, if needed.

Note other heat shrink films such as ultracoat are NOT wide enough to cover a 700c wheel. As far as I know only monokote is wide enough.

There are plenty of colors to choose from and you can get fancy with layers of color if you are so inclined. Mine is basic black.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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Yup. That too. Only thing I'd say is that a heat gun is about 100 times easier than an iron for large surfaces.
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Sounds cool. I saw where one person recommended Stits aircraft covering. That should be really tough but probably heavier.

Is the cover very uniform on each side? What I'm concerned about is wobbles or unevenness in the surface when you spin the wheel that would cause flow separation and defeat the purpose.
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Re: "Best" power meter - money no object [jaretj] [ In reply to ]
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jaretj wrote:
Garmin does now:

https://buy.garmin.com/en-US/US/p/546361

Do they similar for Vector 3 ?

Have kept this a bit quiet considering how many use Shimano cleats
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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Mostly that's a question of workmanship. A slightly deeper rim would make it easier to manage. The R460 doesn't leave much room to work. So a slightly deeper section would just make it a littler easier to work with.

But, I think you are splitting hairs. Not that there is anything wrong with that. That IS sorta what we do around here.

Of course, I did fare the battery cover on my powertap. And it annoys me that it is a concave faring. So, I might be the pot calling the kettle black. :=)
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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IME a rigid cover is never quite right. I seem to have more trouble with the DS, but can get the NDS pretty good. That's my main motivation for looking at Monokote or something similar. The current rim is a XC279, 23w, 28d. I've been debating getting a cheap 80+mm carbon rim and putting a cover on that... because it should be easier to get a good fit on a deep rim, plus better chainstay and derailleur clearance. And in Wheelbuilder's tests, the cover on a deep rim was much better... although I believe fit was probably the only reason for that. Fit is important! Seems like the Monokote would be uniform so long as you get the glue lines uniform. I don't know how hard that is though. And the dish! Not sure about that either...
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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If you want perfect glue lines, just mask off the edge near the spoke nipples with tape. You can spend all day on that if you want, to get it perfect. Apply the contact cement, let dry, and peel the making tape. Then apply the monokote. Should be near perfect.

The hardest part of the whole process is minizing wrinkles on the rim. Just takes some patience. Apply at 12,6,3,9 and the divide. You can use your heat gun to shrink between divisions to pull out the slack as you work around the rim. As noted, monokote is cheap... So, if you aren't happy you can retry your process until you are... Several times before you even get close to the cost of a cover. It's easy to work with, so worst case I'd guess it takes one extra roll to get the process perfect like you want.

The material shrinks a LOT. So, it will be drum tight and glass smooth when you are done. The dish is no big deal. It has no impact on covering either DS or NDS. No drama.

Your xc279 looks almost identical to an r460. Its actually 4mm deeper according to one drawing I found. So, seems fine.
Last edited by: Tom_hampton: Mar 8, 19 19:50
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Tom_hampton wrote:
Apply at 12,6,3,9 and the divide. You can use your heat gun to shrink between divisions to pull out the slack as you work around the rim.

The divide? Can you explain that some more?
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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Almost any Monokote disc should be better than this: https://forum.slowtwitch.com/...ost=3487234#p3487234
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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That's.... amazing ;) If you check the spreadsheet, the CdA (yes he took it to A2) was surprisingly low compared to a box-rim wheel.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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Sorry. Typo. Sound have been "then divide".

The idea is to adhere the monokote just at each point on the clock (12,3,6,9). Then subdivide each of those areas. Keep subdividing until the sections are about 4-6" long. Once you are down to these short sections use the heat gun (or iron) to shrink the perimeter enough to avoid wrinkles as you smooth down a section at a time.

Then use the heat gun to begin slowly working out the slack. Take your time and work fairly large areas until it begins to get taught. Concentrate more on the perimeter more than the center. From then on work smaller areas that are showing wrinkles. Just keep the heat gun moving. Don't over shrink it. Just enough so it's taught, and not showing wrinkles.

Seasonal temp changes may cause it to go a little slack and show wrinkles. 30 seconds with the heat gun will tighten it back up. I check the night before the race and touch up with a heat gun if I find any wrinkles.
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Re: "Best" power meter - money no object [Tom_hampton] [ In reply to ]
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Thanks for the info. Been reading that Monokote is pretty fragile. Since I ride on roads that have gravel scattered on them, I might try dacron cloth used to cover aircraft. Looks like the same idea, only I'd need to coat it with something after it's made.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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Yes. I've done the silk and dope thing on a model RC aircraft. It's more work, and I don't think it would be any better. My silk and dope rc is much more fragile than my monokote.

Don't know why someone said monokote is fragile, because it is not. My first cover lasted over a year. I had to remove it to fix my PT hub, but it was fine. The replacement has also lasted over a year. I ride it all the time. It's my training wheel. The only punctures I've gotten were from me being careless with a screw driver or something. Even then it was just a hole and didn't lead to total failure. It does not just tear like mylar or celophane once punctured. It just leaves the hole.

As I said above, small holes can be patched with electrical or packing tape. Larger holes can be covered with a piece of monokote. It has a heat sensitive adhesive backing. So, it will iron onto the existing cover.
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Re: "Best" power meter - money no object [wintershade] [ In reply to ]
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Why no love for Vectors? Anyone gone from garmin to faviano?

My vectors have been pretty solid for 4+ years now and I “feel” (as measured vs my Neo) consistent.

Never used another brand

Not seen anything yet w these tho that makes me want to upgrade
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:
MTM wrote:
I think they did, but I'm not that versed in Powertap offset values. I was wondering what one unit in the offset (as showed on my Garmin) corresponds to.



Looks like N-m if using Ant+. https://www.powertap.com/...tes-to-offset-values

If I'm reading that correctly each increment is 1 Nm (for both ANT+ and BLE, you just have a decimal point in the reporting value when using BLE). That's extremely blunt at ~10W for each step at 95rpm. Unless your powermeter is quite unstable, better not touch the zero offset at all if that is correct!
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Re: "Best" power meter - money no object [mvenneta] [ In reply to ]
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I have 2 Quarqs and PT G3 that have served me well for several years.

I believe though based on the original thread title that SRM has been a tough one to knock off that “gold standard” of power meters podium especially when cost is not a factor.
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Re: "Best" power meter - money no object [MTM] [ In reply to ]
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MTM wrote:
If I'm reading that correctly each increment is 1 Nm (for both ANT+ and BLE, you just have a decimal point in the reporting value when using BLE). That's extremely blunt at ~10W for each step at 95rpm. Unless your powermeter is quite unstable, better not touch the zero offset at all if that is correct!

Actually it's more like 40 W/Nm at TT speeds. Something doesn't add up here! Unless the number displayed is much more crude than the number stored... ?
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:
MTM wrote:
If I'm reading that correctly each increment is 1 Nm (for both ANT+ and BLE, you just have a decimal point in the reporting value when using BLE). That's extremely blunt at ~10W for each step at 95rpm. Unless your powermeter is quite unstable, better not touch the zero offset at all if that is correct!


Actually it's more like 40 W/Nm at TT speeds. Something doesn't add up here! Unless the number displayed is much more crude than the number stored... ?

Yes, I calculated it as was it the torque at the spider, not the hub, so my number is off. 4x that sounds right when using the hub, which sounds absolutely huge. Maybe Chung's post about it being in 0.1 Nm steps is correct? That would still be 4W/step, so definitely still quite coarse.
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Re: "Best" power meter - money no object [MTM] [ In reply to ]
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He showed a photo of his calibration screen showing "Raw Torque" in 10ths of an in-lb. The offset was still in whole in-lb though. There are 8.85 in-lb/N-m, so 10ths of an in-lb would be ~0.5W resolution.

I have the same computer (Joule GPS) only mine shows raw torque in whole in-lb on that screen. This is also reflected in the .csv files. Even though the torque field is in N-m, it's obviously converted from whole in-lb increments. So resolution is more like 5W at TT speeds.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:
He showed a photo of his calibration screen showing "Raw Torque" in 10ths of an in-lb. The offset was still in whole in-lb though. There are 8.85 in-lb/N-m, so 10ths of an in-lb would be ~0.5W resolution.

I have the same computer (Joule GPS) only mine shows raw torque in whole in-lb on that screen. This is also reflected in the .csv files. Even though the torque field is in N-m, it's obviously converted from whole in-lb increments. So resolution is more like 5W at TT speeds.

Doesn't Powertap statae +/-1.5% accuracy for their G3 hub? It's interesting that their stated accuracy is on the same order as their zero offset steps. Doesn't leave much room for inaccuracies in the rest of the measurement path!
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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rruff wrote:
He showed a photo of his calibration screen showing "Raw Torque" in 10ths of an in-lb. The offset was still in whole in-lb though.
Hmmm. You know, now that I think about it, I'm not sure what units the offset number used, or why it was "centered" at 512.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
rruff wrote:
He showed a photo of his calibration screen showing "Raw Torque" in 10ths of an in-lb. The offset was still in whole in-lb though.

Hmmm. You know, now that I think about it, I'm not sure what units the offset number used, or why it was "centered" at 512.

When mine is calibrated and no load I show 509.0 in the raw torque field, and 509 in the offset. Even though the raw torque shows 10ths, it's always a zero to the right of the decimal, even if I apply torque. Both numbers are in-lb.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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When mine is calibrated and no load mine shows 0.0 in the raw torque field.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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I'm guessing the difference is I have an SL+ and yours is a G3.
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Re: "Best" power meter - money no object [rruff] [ In reply to ]
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A long time ago I had a PT Pro with the LYC, but I don't recall seeing raw torque on a base of the offset.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
rruff wrote:
He showed a photo of his calibration screen showing "Raw Torque" in 10ths of an in-lb. The offset was still in whole in-lb though.

Hmmm. You know, now that I think about it, I'm not sure what units the offset number used, or why it was "centered" at 512.


I can only speculate but considering we are talking about days when processing power and memory in a cyclo-computer was at a premium...

If a display can't show negative numbers (my old PT Cervos didn't), best then to use a large enough positive value as the baseline as well as large enough to provide some reasonable level of resolution at the unit level.

That and 512 is a power of two in binary number system which (along with all units up to 1023) can be stored with just 2 bytes.

Baseline:
(512)₁₀ = (1000000000)₂

One unit above:
(513)₁₀ = (1000000001)₂

One unit below:
(511)₁₀ = (0111111111)₂

http://www.cyclecoach.com
http://www.aerocoach.com.au
Last edited by: AlexS: Mar 11, 19 14:07
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Re: "Best" power meter - money no object [AlexS] [ In reply to ]
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IIRC, Quarqs used to report their calibration numbers in units of 1/32nd of a Nm.
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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RChung wrote:
IIRC, Quarqs used to report their calibration numbers in units of 1/32nd of a Nm.

Yep.

The binary number "theory" is only speculation on my part however.

http://www.cyclecoach.com
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Re: "Best" power meter - money no object [MTM] [ In reply to ]
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MTM wrote:
rruff wrote:
MTM wrote:
I think they did, but I'm not that versed in Powertap offset values. I was wondering what one unit in the offset (as showed on my Garmin) corresponds to.



Looks like N-m if using Ant+. https://www.powertap.com/...tes-to-offset-values

If I'm reading that correctly each increment is 1 Nm (for both ANT+ and BLE, you just have a decimal point in the reporting value when using BLE). That's extremely blunt at ~10W for each step at 95rpm. Unless your powermeter is quite unstable, better not touch the zero offset at all if that is correct!

Just did 10 zero tests with my PT G3 with the dual ANT+ and BLE pod. On a Garmin I got 7 times the value -1 and 3 times -2. With the powertap app I got 7 times -0.12 Nm and 3 times -0.22 Nm displayed. Thus, I guess the ANT+ increment is 0.1 Nm i.e. -1 means -0.1 Nm.

With over 10 years experience with PT hubs, the zero setting always has been and still is a problem. Using auto zero in a TT is like gambling. In out and back courses sometimes I did 20 W more in the first leg, sometimes 15W more in the second leg, although it felt the same effortwise.

PT hubs have some plus points in aero testing but be careful with the zero setting, check it once and than don’t touch it again, the increment is just too large, and don‘t use auto zero!
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Re: "Best" power meter - money no object [BergHugi] [ In reply to ]
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BergHugi wrote:
With over 10 years experience with PT hubs, the zero setting always has been and still is a problem. Using auto zero in a TT is like gambling. In out and back courses sometimes I did 20 W more in the first leg, sometimes 15W more in the second leg, although it felt the same effortwise.
Was this on a calm day (or was there a consistent wind speed and direction)? If so, have you compared the out and back VE profiles?
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Re: "Best" power meter - money no object [RChung] [ In reply to ]
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No VE, VE is not the answer to everything. I just didn‘t skip a single crank revolution till the turning point. At the turning some seconds coasting was enough to initiate auto zero and the power reading changed.
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Re: "Best" power meter - money no object [BergHugi] [ In reply to ]
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VE isn't an answer, it's a diagnostic.

VE is sort of like a microscope, or maybe an amplifier. It can help you "see" whether something changed. That change can be a change in slope, or a change in wind, or a change in the zero calibration offset. It can't tell you exactly which changed but it can tell you something changed. In your case, you suspect that the zero offset changed at the turnaround. VE could (perhaps) help you identify that since a change in zero offset should often be distinguishable from a change in slope, or a change in wind.
Last edited by: RChung: Mar 16, 19 8:45
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Re: "Best" power meter - money no object [BergHugi] [ In reply to ]
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BergHugi wrote:
PT hubs have some plus points in aero testing but be careful with the zero setting, check it once and than don’t touch it again, the increment is just too large, and don‘t use auto zero!

Not sure that is a good idea. IME a changing temperature will change the offset significantly. In hundreds of TTs I've never experienced the autozero failing. There was one where the readings were oddly low, but they were low in both directions and I'm pretty sure I coasted enough at the turn for it to reset. I really wish there was a way to record the offset in a file.

.1 N-m is about the same resolution as 1 in-lb. Still much too crude. And I still don't understand how RChung is getting .1 in-lb resolution on his.
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