Does anyone regret getting a single sided power meter vs dual sided?

Since I made the original thread, I just wanted to provide some updates. I went with a Stages L only. The reason I got a Stages L instead of a pair of Assioma Duo pedals was that I got a great deal on the Stages. I used the 20% Clever VIP coupon on their website and it came out to $280 USD for an Ultregra L crank. Decided to save some money as the lockdowns were ramping up in my province and I wasn’t sure if I would still be employed. Good news is that I’m still employed, bad news is that the stages L and my Kickr Core is quite off ( ~10% on avg). See the comparisons below.

Andrews + 1

Part of Holt Hill + 1

Part of Juneau - 1

I’m still using the Kickr Core power reading to keep consistency until my next ramp test where I’ll be using stages L instead with powermatch. Yes, I’ve done spindowns and zero offsets on both devices.

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I haven’t drilled into that level of detail, but just on this morning’s ride, I had TR paired to my Kickr Core and Zwift running ANT+ to my Vectors, and the readings were about 5% different (Core was ~5% higher). Eventually paired the Vectors to TR and carried on smartly.

Lesson learned: do your Zwift races with your smart trainer providing power! :smiley: (Why didn’t I think of this before now??!!)

I had previously trained with a stages left only power meter without issue. I think as long as that is the only power meter you use, they are consistent and that is all that matters. However, I upgraded my crank and got a Quarq Dzero, and noticed consistently lower power than my stages, which was a little frustrating.

I have also just purchased Assioma Uno pedals for my new TT bike, and also, this is reading around 10% higher than my Quarq Dzero. In my case, I am convinced that it is because I am left leg dominant. I have a stronger left leg than my right, and although according to my Quarq, my power balance is pretty even, the Quarq does not really read both sides, it just estimates based on the area of the pedal stroke that the power is applied. There is a youtube video in which a quarq ‘dual sided’ meter is compared to power pedals and it is clear that the quarq reads power on both pedals, even when only one pedal is clipped in and the power pedals are reading 100 / 0 on the balance.

Due to this discrepancy, I have just ordered the upgrade pedal from Assioma, and hopefully this will confirm my theory that my left leg is more dominant and this will even up the mismatch between my pedals and Quarq. (even though I would love to have an FTP of 330 rather than 300, I don’t buy it).

So in answer to the thread, do I regret having single sided power, yes, but only because I also have another power meter on another bike that does not compare accurately. I am leaning towards using my Assiomas on all my bikes and selling the Quarq to have consistent power between bikes / indoor trainers.

As others have said, if you only have one power meter and it is single sided, it is perfectly fine and I was happy with my stages for 3 years when I just had one bike.

Doesn’t any spider-based power meter (Quarq, SRM, etc.) measures the power of both legs?

They give power from both legs, but the way they measure is not by taking a measurement from both sides. It takes the power applied from different parts of the pedal circle and estimates from which leg it comes. It measures total power, but it is only Pseudo dual sided power not true figures from both sides. I have been skeptical of my quarq as it pretty much always has me at 50 / 50 or 51 / 49, when my left leg is stronger.

There is a DC rainmaker video in which he compares the output on power pedals (Garmin I think) vs a Quarq power meter. The quarq only goes down to something like 75 / 25 balance even when power is only applied to one pedal with the other one unclipped, whereas the power pedals clearly go to 100 / 0.

Here is the video.

I did regret getting a single sided power meter. I was having a lot of trouble to hit the required power on some intervals because my left/right offset is not constant. When I need to push high wattages at high cadences my left leg starts to slack compared to my right leg, which means that when TR wants me to hit 300w, I really need to hit 315w so the left sides power meter can reach 300w. This was really affecting my training so I recently upgraded to a dual sided one and not only that problem went away, but also is now much easier to hit and maintain the required power at all intervals.

In the end, I would say that one sided power meter is much better than virtual, but there is a significant jump from one sided to two sided.

My Assioma duo upgrade pedal arrived, and I am able to say conclusively that in my case, only having Left sided power grossly overstates my power due to my stronger left leg.

Here is a comparison of a ride between my Quarq dzero and Assioma duos, very closely aligned.

Here is the left right balance, with a large discrepancy between my left and right on the Assiomas. Interestingly the Quarq has me very even, which shows that its left right measurements are just guesses. The darker purple lines at the top and bottom are the assiomas.

And finally, here was a ride from a few days ago comparing Assioma Uno with Quarq Dzero which was perplexing me and causing me to question the accuracy of both my power meters as the Assioma is always at least 10% higher:

So my take, in my situation with more than one bike / power meter and training indoors as well, I need consistency and my left right balance means that having one of them being single sided screws up my data to a material level. That said I did have a stages left only for a couple of years when I used only one bike and it was perfectly fine for training. Left only for me would put my FTP at 330 rather than 300 ish, which although that would be nice, is clearly not accurate.

I have been so impressed with the Assioma in the few days I have been using them, and with the ability to switch between bikes so quickly I am questioning if I even need the Dzero now, even though it is a great power meter.

Looking to pick the collective brain. I’m seriously thinking about adding power meters to my 'bent trike. I’m not looking for anything super accurate. Just good enough to give an indication of how I’m doing. I use TrainerRoad for indoor rides. For those rides, power is calculated by speed and the power curve for my double overdrive trike rollers. What I’m wondering is, is whether or not a single sided crank based meter is going to do the trick. I don’t cringe at the thought of $3-400. $1000 makes me flinch.

Thoughts?

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Yes. Single sided is fine.

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Yes.

You might have a discrepancy between your legs, meaning that the L-side Watts x2 is not strictly ‘accurate’ but it will be completely consistent as you continue to train.

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Nope. Dual power or death.

And nothing under $1K.

You want to fast don’t you?

:grin:

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Until you can push 53x11 at 95 RPM or your FTP is over 400w…single is good enough. :+1:

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Unless, of course, his L/R balance varies with power, cadence, fatigue, etc… which it usually does

On that basis single sided is absolutely fine. Full disclosure, it’s what I use and I love the data it generates.

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I got a Stages recently and my outdoor 20 minute power is around 60 watts less than my indoor 20 minute power (Tacx Vortex calibrated after warm up).

Honestly I’m not sure what to make of it. Either the Tacx is way off or the Stages is way off, or they are both off by a good percentage.

Mentally, it’s a blow as I thought I was edging close to 300 watts for my 20 minute power. The bottom line is that I have no freaking idea. I do have around 30 Strava KOMs so I know that I’m not terribly slow.

I emailed Stages and they gave me some ideas on a factory reset and sending them some info. I think I’m also going to do some more scientific head to head comparisons. I have a Powertap to compare against and I have another bike with a Quark I can compare to my Tacx. I’m going to try and triangulate the power between all these power meters and my Tacx.


I think one thing this brings up is the NUMBER we all think about. On one hand the actual number is meaningless as long as the power meter is consistent and you only use one power meter. I could just train to the Stages and forget about everything else.

One other thing I finally noticed is that if I consciously pedal in circles when I’m using the stages I seem to get higher power for the same perceived effort. Either this is telling me that I should work on my pedal stroke or spider based or hub based power would measure a little better.

My conclusion is that single sided would be fine for training. It depends on what your big picture training view is. For the most part you are going to be training at intensities that are below threshold or a little bit above. Between your power meter, HR monitor, and RPE one should be able to hone in on the right zone and do effective training.

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So what difference does that make to the power/targets as measured by a L-sided PM vs. Dual-sided?

As far as I know all the science looking at ‘pedalling efficiency’ suggests efforts to correct imbalances make no difference to performance anyway.

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The only thing my dual-sided power meter has shown me over two and a half years is that I don’t need a dual-sided power meter. Single sided is fine for most athletes.

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I have single sided power. I feel that as long as you have a consistent way of measuring your efforts it works just fine.

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Single sided is fine.

@mcneese.chad
Merge with…?

Does anyone regret getting a single sided power meter vs dual sided?

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FWIW my Stages gen2 and gen3 and Kickr direct-drive have all been within 5-10W of each other. But the Kickr appears to drift a bit and I have to let it get warm for 20+ minutes before doing a spin down. Also FWIW our gym have Stages SC3 bikes with single-sided power meters, and by feel everything matches up.