himespau 

If it's reproducible and you calibrate your workout to it and max's derived from it rather than some raw numbers derived elsewhere, shouldn't that be enough to get good training in? Calibration seems like it wouldn't be an issue as long as it's consistent, but then what do I know?

Bob Dopolina 

+1.

The only issue is comparing numbers in some pissing contest. If the unit is consistent and accurate enough you should be able to use it as an effective tool.

I'd like to see so 3s numbers.

svtmike

Accurate readings from any crank-based power meter should be higher than a PowerTap reading, as they are before drivetrain losses.

As others have noted, you really need consistency rather than absolute accuracy. The absolute accuracy does come into play when you are using multiple devices in a training program. You can have that issue just using multiple PowerTaps.

I agree with the assessment that it's a power meter for the recreational roadie. The price point and compromise of measuring the output of only one leg seal its fate there -- but any quibbling about that is really just disappointment that they aren't developing a $700 SRM.

I still like the concept, am interested in seeing it come to market, and I hope it works well enough for those who haven't been able to live with the limitations and/or expense of the PowerTap, SRM, and Quarq solutions.

jsutkeepspining

but u can get powertaps for $700 (or less)

grolby

No, drivetrain losses are well within the error range of crank-based and hub-based power meters. This is simply wrong. Drivetrain losses between the two would be indistinguishable from noise in the data, an SRM isn't going to read higher than a PT if they are both accurately calibrated.

Bah Humbug

Yeah... but this lets you swap between training and race wheels. Or jump on a great deal on a last-year-wheel. Or grab one off CL/eBay. Or swap your PM between your road bike and your 'cross bike. This is the one I've been waiting for. Just need to see how handy I can get swapping left crankarms now.

svtmike

You sure about that? I've seen measurements of 2-5% with a clean lubed chain (Example). That's outside the quoted accuracy of the PowerTap that others have mentioned, and outside the claimed accuracy of the subject of this thread.

RChung

Racer Ex 

Incorrect. If it's going to be inaccurate you need consistent inaccuracy.

You're assuming a consistent percentage of error but that's not what's shown in the sample. You can't train or race on a unit that's 3% off at 200w, 10% off at 300w, and 20% off at 400w, unless you're going to ride along with a calculator or slide rule. And you'll note that the unit isn't even consistent. In some samples it jumps 80w over the PT, in others at similar PT readings it doesn't.

People that actually have something other than theoretical experience with PM's and their application in training will look at this and go:

"Not good"

svtmike

Whatever. I'm not trying to convince anyone that it's a diamond or a turd. I own 3 PT's and have been training with the power data for a few years, so my experience isn't purely theoretical thank you very much.

Bob Dopolina 

I'd agree with that qualifier.

AdelaaR

Indeed.

topflightpro

I'm not surprised.

Ex's assessment of the power variation is spot on. If the power fluctuates too much, it isn't a useful training tool.

And to clarify my point on Ergomo, regardless of whether it worked, the company has folded, meaning no more support for the products. That ultimately puts it as a failure.

Bob Dopolina 

The company was sold (not folded) and is back in business. I had my unit serviced earlier this year.

Racer Ex 

You're welcome. Having trained with a PT I'm frankly surprised that you didn't have qualms about the 80w spike on the 30s smoothing. If my math is correct that's a 20% error.

Looking at the test graph from a coaching perspective that would be a nightmare. Aside from the chart showing that it was inconsistent in over-reporting, it wasn't an across the board adjustment but seemed to be extrapolating.

In any case you can't buy one yet. After waiting out Metrigear for several years and the Look unit's price estimates and delays, you have to be a bit jaundiced.

svtmike

I'm just looking at it from a basic training perspective -- what's my target power for an interval, what did I achieve in a power interval, what's my NP/AP/TSS/TSB/etc. A 20% error in 2% of a sample isn't cause to say the thing will never be worthwhile or is completely useless for training. I would agree that it is enough to say it's certainly not ideal or best-in-class. Measuring off of just the one leg might be the problem here -- perhaps that rider has a stronger left than right, etc.

From a coaching perspective, it might not be ideal but if your athlete does not have a PowerTap or SRM, and rather has this, is it so inadequate that you couldn't coach at all from it?

Because this company has working units of an older design in commercial exercise equipment, I think they might have a better chance of hitting the market than the pedal- and cleat-based guys have shown.

merlinextraligh

And the $699 seems somewhat misleading.

It's $1349 for DA including the crank.

While there is a $699 price for 105, but that's without the crank, and the say they don't retrofit,so the actual price is going to be something north of$699.

I bet actual price is going to end up above $699, and it will be after Jan 1

canam73

So what is the StageOne measuring? Flex in the crank arm?

Phantoj

I'm guessing strain in the crank arm, which might be tricky because the crank arm is deflecting in different ways at different times (torsion, in-plane/out-of-plane bending, shear, elongation).

neneboricua

Thought it was $699 for the left crank arm with the power meter attached? So if you already have a crank, you'd have an extra left crank arm lying around.

zigmeister

They have thousands of these and they are on stationary bikes. Ive used one, pretty accurate from what i can tell. They hav e a grwat deal of experience and history. That stationary unit is the model this one is based off of which they have tweaked, reduced the size and profile of this one. It attaches to the left cranks arm works the same way. Of course they have BT and ANT built in this unit also.

zigmeister

So does the powertap on the 1 second graph. Powertap shows high readings 40w at times. Plus, we dont know what the person was doing at those peaks. A 30 second interval where their left legmis concistently the more powerful leg.

Ive seen similar thngs with powertap and power2,ax comparison. Just not as extreme. But the are consistent.

gregf83 

How could you tell? Did you compare your data with a powertap or other known powermeter?

They may have history providing data for indoor trainers in dry, temperature controlled environments but making them work consistently and reliably outdoors is a little more challenging.

I'm in the market now for another powermeter and am looking at either a used SRM wireless, quarq or another powertap. The prices on the StageOne don't look attractive to me, particularly when you factor in the unproven performance and only getting half the data.

Something it caused me to think about is whether I start a sprint with my left leg or my right leg. I honestly have no idea if I favour one leg over the other when starting out. I meant to check on my ride today and forgot.

merlinextraligh

The article is less than clear. They say they aren't going to retrofit, so I think you need to buy from them, at least the left crank arm.

nhluhr

I can't believe anybody is defending or worse yet, considering spending $700 on this worthless device. I'm not sure why anybody would ever want to measure only their left leg's power.