Treadmill testing provides a decent standard for assessing measurement of steady state power output but fails to ascertain the performance of power meters at high power outputs and under acceleration scenarios.

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http://www.cyclecoach.com
http://www.aerocoach.com.au

If only someone had thought of that before.

(BTW, the acceleration due to gravity does vary across the surface of the Earth).

Indeed, there is a variance of approx 0.5%.

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http://www.cyclecoach.com
http://www.aerocoach.com.au

What is the current standard? Static weight tests?

The treadmill test is interesting, but does seem to introduce errors (gravity assumption, holding a straight line, rpm, other measurement errors on treadmill angle or speed, etc...).

I wonder if hanging weight test over a spectrum of weights would be better.

Anyway, I do dream of a world where my PM readings are consistent across PMs. I would even be happy with a manual offset that I could use to equate spider to crank to pedals. I know they should be different, but from a user perspective I would be happy if they all read the same (+/- some margin for error) for the same effort.

Maybe SRM's science ergometer? Hooking it up to a bread toaster and a voltmeter? Hanging a rope to the wheel and measuring how quickly you can pull a known weight up a cliff like for horsepower?


Not sure how that would work for pedals. Inside, middle or outside of the pedal?


See above...

That works for getting torque right on crank-spider and rear hub models but it doesn't work for pedal power meters. In addition, you still have to get the cadence measurement right, which can be surprisingly hard with the systems that use accelerometers. Some (most?) power meters have problems with non-round chain rings.

The treadmill test can work reasonably well for steady-state power for all sorts of power meters, but it may not pick up sudden transitions in power well, or peak power.

I use a combination of several different methods to check the accuracy of my PM, but I understand that would be too much of a PITA for most riders.

Interesting point! I have a Tempo power meter and it has that feature to correct it. I was able to offset it so that it measures exactly as my power tap!

I also have a TEMPO Power meter and it does have it! In fact, the TEMPO uses a gyroscope to measure cadence, that is why the power reading change is instantaneous and responsive. This guy has been developing small batches of these power meters for years and he is an engineer from Motorola. It is A US based company (in FL), very low profile but what a quality gadget they have and I can tell you, the reading from this PM are exactly on point with every other PM around from the big guys (i.e. stages, 4iii, etc.) In fact, he offers a full satisfaction warranty so if you don't like your PM for any reason (reasonable, that is, not because you don't like the color) he would give your money back.

I read about this guy in several cycling magazines a couple years back but could not find any info till I contact them directly and after asking 200000 questions and getting them all answered I pulled the trigger and I cannot be happier. I am not quite sure why DC Rainmaker has not reviewed this PM since he has even reviewed some very crappy ones like the AROFLY and the mockup Chinese ones, wold love to hear what he thinks about it.....just my $0.02

P.

Woah, two guys who don't post much both love the same rare power meter and happened to land in the same thread! And one of the guys is a friend of the developer! Man, what are the odds?

My 0.00c on the TEMPO. First up - I've never heard of it.

Five minutes on Google later...

Right. It was a well underfunded Kickstarter fail. Compare this to the insane hype around the IQ^2 (also a budget power meter on Kickstarter). Why did TEMPO fail... and so hard? Being ANT+ only is DOA in this day and age. The very few photos I can find of the unit look like a chunk of chewing gum stuck to a crank. If it's not pretty, also DOA.

If the unit is unknown, already outdated, ugly as sin, and nobody is asking or searching for it.... why would anyone review it? Personally I'd have a look and perform comparisons out of my own interest, sure. I can guarantee the time to produce content on it would be wasted as it wouldn't gain many views and repeating what I've said about it isn't cause for a happy ending video.

There's more to just accuracy to make a power meter successful. Case in point, InfoCrank. Wait, ANT+ only again. God damn it.

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Shane Miller - GPLama
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It's only been discussed a couple of times on this forum before. Once was here, in a thread started by one of the guys in this thread: https://forum.slowtwitch.com/...ost=5446569#p5446569

A second time was in this thread, started by the same guy: https://forum.slowtwitch.com/...ost=5867573#p5867573

Then about a month ago there was a post in the classified forum offering a few for sale.

The fact that the TEMPO is yet another left-leg-only power meter probably also had something to do with their failure to really take off.

As for InfoCrank, I don't see it being ANT+ only as a significant limitation. OTOH, they are more expensive than many other offerings, and most people have very low standards for data quality and thus are unwilling to spend more for it.

I don't understand why you say that?

Interesting point of view...........everyone has the right to an opinion. I just can talk for myself and my experience and yes, it is ANT+ only but that's all I need to sync with my Garmin units, no need for Bluetooth. I agree with you, it might not be for everyone and some people would find it inadequate based on the features asked by the user. Happy to share my data from my last IM to anyone who might be interested.

P.

Sorry, your confusion is because I was confused. I was jumping ahead in my thought process and confused things. This thread began with the treadmill test, so I was thinking about advantages and disadvantages of the treadmill test compared to static calibration and conventional dynamic calibration. Static calibration works fine on pedals. The problem is that conventional dynamic calibration rigs weren't designed to work with pedals.

I did know him and was doing him a favor. He helped out my fam with us barely being acquaintances so I thought I do him a solid by mentioning him. Aside of that, its not a chewing gum on a crank. (lol) Given how this thread has gone, I'm not even going to mention his website where you can pick one up today and see a bunch of photos. It's pretty polished.

But the point I want to make here... This is our sport, an expensive one at that. If we want to keep paying $2K for pedal power meters and $5k for a frame $3K for wheels, and $2K for a groupset, then fine (I'm exaggerating..a bit).
Bringing more people to the sport will lower cost. People aren't going to cycling and triathlon as much if things are so expensive...There are two ways to help bring the cost down. Support new ideas or do something about it and create something. None of which have occur in discussions I read on ST.

Sooo the way I think of it is if we support instead of bash people trying to do something about it, maybe it will create competition and lower prices for us all. Who knows, maybe if he was supported, he would have a $500 dual sided pedal by now. What incentive do we give innovators to continue if we destroy them online without really knowing anything? All it does is hurt us all in the long run.

Nitpicking by people who have designed exactly 0 power meters is not going to help anyone.


Better offereings? I picked up an R8000 Ultegra for $350. Try getting a single sided working,accurate meter for that price anywhere. Pioneer is $560, Stages $580. That's my $0.02

Ah, gotcha.

Me, I just pedal my Vector-equipped bike on my dynamometer (Velodyne), which in turn I validated 20 y ago using a statically-calibrated SRM. Easier than riding a bike on a treadmill (I have done that too, at least back in the 1980s), and more precise than using, e.g., Chet Kyle's old custom-built calibration rig.

4iiii has two different offerings that they'll install on your existing R8000 left side arm for $399. And they're currently offering a power meter on a 5800 crank arm for $360.

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"They're made of latex, not nitroglycerin"

Thanks Gary, but I meant that the meter came already mounted on a brand new r8000 for $350. Didn't have to send them my crankarm. It's similar to stages, you get the arm with the meter. I sold the arm that was on bike for $80 and replaced it with the meter that I got on the new crank so net it cost me $270 for an r8000. I did consider 4iii, but I would have had some downtime without my left crank. My second choice was stages but it was a bunch of money. I do have a stages too and powertap. The stages is on its last leg. Powertap is still good. Just personal preference.