rubiksoval

Just buy the wheel. It's as easy as putting the wheel in the dropouts.

ljsense

I guess I'm lucky then. My numbers were never off between left and right by more than 2 percent, and it was usually right at 50/50. Assumed most people were like that based on the success and accuracy of single-sided systems. And the lack of people who spent their formative years only using one leg to walk, ride a bike, etc.

guadzilla

Ha, you are lucky. I got Vector 3s for my wife and they were a fricking nightmare. Pedal would stop sending data, low battery warnings after a couple of hours, etc. Finally sold them off and got her Assiomas. Those are much better, thankfully.

asgelle

Good one. Funny.

ljsense

I get the feeling you sell dual sided power meters, expensive bike fitting sessions or something like that.

asgelle

Why? Are you invested in single-sided ones, or do you just like misleading the competition so you have an advantage for yourself?

phrantic09

I used a little avocado oil on the contacts and have never had an issue with them. Maybe I’m just lucky though, have heard that others had issues.

RChung

I don't sell power meters, nor do I fit riders. The guy who did this study (from 2017) doesn't, either.




Sky/Ineos famously is sponsored by Stages. When Sky/Ineos riders do testing that really matters (like, aero testing on a velodrome) they switch to a different brand of power meter.

This isn't to say that the Stages isn't a good choice for many riders, or that accuracy and precision don't matter to you. It's just to say that Maier's study shows that there are differences among power meters, they're not all the same, and that it does matter for certain uses.

ljsense

RChung, the other guy was suggesting that it's common for one leg to produce significantly more power than the other -- and went further to say it could vary back and forth; some days the left might come on strong, but wait, here comes the right, and so on. That doesn't make sense to me, but it may well be for some people; I don't know. Maybe you've got a scatterpoint and a linear regression on it.

I was just saying that in my experience, I didn't see any significant difference at any point between my left and right pedal strokes, and am happy with a Stages. It always connects. The battery lasts a long time, they're pretty cheap, etc.

In your chart above, some of the Stages plot points are more accurate than some of the SRM plot points, and SRM is always held up as the gold standard. So, I think it's a decent argument to say that a single-sided power meter, whether it's a pedal or crankarm, can work just fine -- especially for someone like the person who started this thread.

Bah Humbug

I absolutely change from 52%L to 52%R depending on fatigue and output. Sometimes it’s higher than that... and that’s average for a ride, not specific moments.

Funnily enough, the people who are most adamant that single-sided is accurate are the ones with the least data to support it.

Seattle Forrest

I expected my balance to be 50/50, too. When I got the Vectors at first I thought they must not be working right. Did a ride on a different bike with a different set of Vectors and I got the same answer. Left leg dominant even though I'm a righty. It's been anywhere from 55/45 to 48/52. The more fatigued I am, the further it is from balanced. And then I hit a step hill and it snaps to 50/50.

If single sided is getting the job done, there's no reason to drop the $$$ on a different meter. Repeatability is more important to most people and it sounds like you're happy with that.

asgelle

That is not what I was saying. At 150 W, a rider might be 45/55; at 200W, 50/50; and at 250W, 55/45.

ljsense

Hey my man, if you want to jump all over my grave screaming that your power meter was accurate within 2 percent, and mine was only within 3 percent, knock yourself out.

I looked at my data from a year of having the PowerTap pedals, which for me required a lot of fiddling with the battery covers and rebooting this or that to work, and I didn't see anything in the data that made that aggravation seem worthwhile. So I switched back to a Stages, and I think if you're looking for a cheap power meter, getting a one-sided one that actually measures forces instead of just taking a guess based on speed and whatnot is a valid suggestion.

My question is, if you know your left leg was putting out 52 percent while it was on the shady side of the street or something, what do you do with that knowledge? What's its value to you?

ljsense

Right, like maybe the left runs on diesel and the right on gas. I just didn't see anything remotely like that in a year of using the dual pedal meters. It was always 50/50 +/- 1.

What I wonder about, though, is if you saw that, what would you do? Would you try to correct it somehow or just figure that's how that body works?

Bah Humbug

I do nothing. If I were particularly concerned about power balance I would probably run power meter pedals to get a more accurate balance number. However, all I care about is total power, but that means true total power, not double my left power, The fact that my Quarqs show a balance value is just another chart to look at, but I place precisely zero value in it.

The problem is that if I do a ride at an average of 200w, and 2% error means it could be 196-204w, that's one thing. Then we add a potential imbalance and it could be 190-210w, we run out of the data having any value whatsoever. Especially since that's averaged over a ride - it might be much worse over a climb, or a sprint, or worse over both but they average out to accurate in the end but the power "measured" during each is horribly wrong.

ljsense

Ok, to be honest, if I had seen that my left/right output varied a lot, I probably would have done the same thing and stuck with any of the systems that measure power on both sides or at the hub. Fair enough.

My bias is assuming that my experience is universal.

tomato coupe

Your experience may not be universal, but your bias certainly is.

RChung

I wouldn't say "always." Not by people who know how to measure accuracy and precision.

That study, by the way, was mostly of power meters "out in the wild" that were on bikes that people were actually using and brought in for that study (plus a few SRMs they had in the lab that were constantly checked and calibrated). Since the data were collected in late 2016, there were few Vectors, Polars, Rotors, P2Ms, and Verve Infocranks. There were relatively many SRMs, Power Taps, Quarqs, and Stages.

Bah Humbug

My point is that it's not "a lot", and I highly doubt your power balance is within 1% of 50/50 across all parts of all rides. But hey, if you're happy, you're happy. I wish I were as smart as the Stages guys were that people would be happy with something that spat out a number.

ljsense

I grew up with another weirder gimmick, the Powercranks crankset, which I still ride to this day. If you're not familiar with it, the company that makes it throws out more claims about its effectiveness than Dr. Bonner does about his soap. But since each leg has to operate independently, maybe it led to a balanced pedal stroke. All I know is, the left/right thing was even for me, and when I compare my Stages data to smart trainer data or other power meters, it all seems right on the mark and useful.

spelger

let me begin with the fact that I do not own power meter. That said, unless the meter is physically attached to your legs then the meter is not measuring leg power either. Both measure a cyclists power output via a proxy. Just a different one.

sfrider 

I'm consistently 53:47 L:R at low effort, and this climbs to 55:45 at peak intensity. So the Stages left sided crank meter I have overreads by 3% at low effort and 5% at higher. That's still fine for endurance use though since its purpose is to measure power droop over time (and to help me pace myself). The Favero Assiomo Duos I have on the other bike are far more informative with power phase, PCO, etc.

My imbalance could be due to my left leg being slightly longer, by a couple of mm. Not really noticeable in daily use, but I might add a 1.5mm insole to the right shoe at some point to see if that makes a measurable difference. I'm just loathe to tweak biomechanics when they're otherwise dialed in. I guess I'm trying to decide if it's worth the risk to try to fix.

rubiksoval

Come again?

Power output. Both are not measuring power output. One is measuring the amount of torque applied via strain gauges, the other is measuring opposing forces.

Two entirely different things.

WhyFi

I think that you should be doubling that error. If you're at 400w total, 55:45, your left leg would be putting out 220w (vs 180w of the right leg) and the Stages would then double that to 440w, which is a 10% difference vs the real total.

guadzilla

I used machine oil and that helped reduce the issues, but she still reported an occasional "low battery warning" that would then go away. In the end, it just wasnt worth the drama. But a couple of other friends - including one who rides 20k km a year - have not had issues either, so i suspect its a bit hit-or-miss. Glad to know yours are working well.

I got a single sided Stages PM - back when they first came out - to put on my rain bike, thinking i didnt really need an expensive power meter on a beater bike. The numbers were around 20% off. I sold it and got another Quarq.