RChung

Oh dear.

To the OP: Sorry.

msu2001la

FWIW, the power numbers from my single arm Stages meter roughly match the numbers from my Wahoo Kickr. I've tracked both on the same indoor ride just out of curiosity and was surprised at how similar they were.

caloso

My Stages left crank arm reads about 5% lower than my Quarq, so it's conceivable that they are both perfectly accurate and that my right leg consistently puts out 5% more power. But all I really care about is setting correct workout levels so I get a good training response. So, as my dad likes to say, close enough for government work.

colnago62

If you don’t want others to respond, pm him.

Seattle Forrest

Most people only "need" to know total power. I think (but could be wrong) that the consensus is even if you have a consistent imbalance between legs, you should try to improve the total power you're putting out by increasing your fitness. If you're consistently at 47/53 or whatever, it's probably because one leg is slightly longer than the other, or something like that, you've found an efficient way to play the cards you were dealt, focusing on the imbalance is likely to be counterproductive. You don't get the R pedal to know your L/R balance, you get it to know not guess how much power you're making.

With that said, I've found the L/R balance and platform center offset extremely valuable in recovering from a foot and ankle injury.

macabio

I have the same issue, a 50 watts difference between my stages (higher) and Quarq. i compared the data in bikecalculator and confirms te exacts numbers for quarq data, and 50watts high for stages. the 12-15 lbs heavier rider will just add maybe 15 watts to your ride.

RChung

That must be frustrating. Are you still using the Stages?

GhostRider62

If you want to compare power meters, enter the PM calibration mode on your Garmin and hang a known weight off a level crank arm. The Garmin will display the torque value. Do the same on your buddy's PM, the torque should be 0-4% within each other. My one G3 PM is 2% higher than true, one is 1 % low, and another is 1% high. It is too early to do the math, but you can also compare the measured torque with the known weight times crank length. I have not carefully assesses a new SRAM AXS crank PM other than to compare against one of the G3 Powertap hub meters at 200 watts and I could not see a differences.

WRT to L/R balance, I am recovering from a crash that messed up up whole left side of my body including a cracked trochanter. One of the muscles under my thigh (goes from the knee up to my butt somewhere) cramps or hurts as the ride gets longer. I checked my L/R balance and it is fine early in the ride but goes to 40/60 as the hours wear on.

burnthesheep

Honestly, in the geek out aero testing community where meters have to read something useful with respect to accuracy.........the left only Stages are pretty much regarded as novelty "kilojoule counters" or "calorie counters".

The doubling a single leg really tosses any accuracy. Sure, it might be precise in reading the same incorrect doubled power all the time. But that doesn't help when you're either 20 or 30w low or high because of it.

A modest 45/55 split would generate the following differences:
100w- 100 = 45 + 55........Stages sees 45w * 2 = 90w (or 110 for stronger left leg)
200w- 200 = 90 + 110.......Stages sees 90w * 2 = 180w (or 220 for stronger left leg)

You can reverse that for a stronger left leg than right. Most folks are weaker left leg.

I feel like most folk's power split improves from the 7% to 5% difference to more like 2 or 3% near threshold though. Mine does at least. Some folks do not. So a 5% difference at 300w can be like 30w higher than actual.

Meter companies with some single sided stuff are now starting to eat the humble pie and allow a "%" adjustment in the settings to fix this. Some allow you to custom alter the curve. Stages does not.

I'm considering dumping my Quarq and Stages across different bikes to just the Wahoo's. But, waiting for some solid accuracy data to come out first from a few different sources/reviewers.

My one left only Stages on the road bike reads silly low. On some little short 9% grade hills in town, I'd have to weigh like 135 lbs for the power figure to make sense for my speed ascending. That doubling can really get ya.

rm -rf

My left only Stages is perfect for me. I'm not looking for absolute accurate power numbers -- I'm not trying to model my aero profile, for instance. The Stages is "close enough".

It tracks my Kickr power quite well, and is consistently lower in the 5% range -- which makes sense, since it's after the drivetrain losses, and perhaps leg imbalances too.
And it reports reasonable watts for steady steep climbs that compare to online bike calculators for that grade%.

I just did an early spring ride, with a longer climb, and it worked great for pacing me up the climb. That's way more useful than perceived exertion or heart rate for pacing. I upload to Golden Cheetah, not for setting a training plan, but for analyzing rides and fitness. I have a good idea of my 30 second, 60 second, 5 minute power numbers. Very useful.

~~~

I don't really care if it's off by 10%, as long as it's fairly consistent. Changes in my own power numbers are what I want to see. Do left-right imbalances change a lot during a ride or during a season?

I even considered upgrading to a dual sided Stages. But it appears that the chainring side power numbers can be quite inaccurate due to the crank and spider design? So I decided not to do it.

GhostRider62

See my earlier post. It can.

Andy Somnifac 

Sure. My initial rides show that my L/R balance can vary greatly in lower-intensity rides, and it comes closer to 50/50 as the intensity increases.

asgelle

For slightly better accuracy, hang the weight with the pedal slightly below horizontal then rotate the cranks backward to slightly above while watching the torque. The highest value will be when the arms were level. That removes any error there might have been in leveling the crank arms.

tomato coupe

Since this thread has come back to life ... I have two power meters that consistently show a 52/48 or 53/47 imbalance. But, one (P2M) shows R higher, and the other (Vector 3 dual) shows L higher. Go figure.