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

I don’t think it has for me but I can’t speak for others.

I’ve got a 4iiii single sided coming in the mail today. Hope I dont regret it…

IMO…I dont think there is a readily available absolute measure of power. I have a wahoo kickr. It’s power could be off 50 watts or more…I wouldnt have a clue. As long as it is consistent…I can train consistently.

Same with the single sided IMO. I’ll be able to dk workouts based on power outside. And hell…lets say WORST case scenario is I have something really weird going on, where one leg fatigues at a wildly different rate than the other…say creating a 10% discrepancy at different times of the workout. Even 10% discrepancy will result in Work performed largely in the correct zone.

So…is dual sided better? Sure. But…999 gram frame is also ‘better’ than a 1000 gram frame. How deep do we really need to go for marginal gains?


I have a left side only Stages PM, I’m very happy with it. Excellent training tool!

Got 2 single sided power meters on different bikes. I have never found it to be an issue not knowing the Wattage the other leg is putting out.

I saw what you did there.

Huh?.. If you’re doing, let’s say 4x10 min at threshold for a workout. You’re FTP is 250 watts a 10% discrepancy is 275 watts or 225 watts the other way. Trying to do your LT work at 275 watts is going to put you in Vo2 max and 225 watts would be below the threshold zone at the top of tempo.

Totally hope it works out for you but 10% does make a difference when training and it gets even more complicated as you get more bikes. I’m sure all of us would kill to have a 10% higher FTP and that would make a huge difference in our riding.

Just ordered a Stages for my Cannondale crank. I would prefer dual sided but there’s nothing on the market that would work for someone who swaps between chainrings & spiders, and I prefer SPD-SL to any other pedal. So it will have to do! If you buy any PM get a new one with a warranty. I had a Specialized brand PM last year and it literally fell apart after a month. They replaced it and I sold it, added some $ and got the Cannondale Stages for my new bike. I would be out a lot more if I was stuck with my dead Specialized meter.

If you consistently train with single-sided, what you say doesn’t matter one bit. You’d test on the single-sided, get your FTP from that, and base all your workouts off of that measurement. Here, precision matters more than accuracy. If your single-sided is off by 10% from what a dual sided would read (it won’t be), you’ll never know it and the only thing affected is your own ego either way.

If you have multiple bikes with multiple different power meters, they’re going to be different regardless of if they’re single- or dual-sided. But that’s why I opted for Vector 3s to keep the measurement the same. Even still, due to different geometries and setups, your FTP on one bike probably isn’t exactly the same as it is on another (esp. for TT vs. Road vs. MTB). Last time I checked, my road bike FTP was roughly 15W (about 5%) higher than my TT bike FTP in aero position on the same PM. The only way to stay truly precise is same setup, same PM.

All that to say that precision matters a lot more than absolute numbers. In ~99% of cases, a single-sided PM is going to end up within the margin of error (1-3%) of what you’d get from a dual-sided PM, so as long as your measurement tool of choice is consistent, single- vs. dual- doesn’t matter for ~99% of people.


Hrmm. More importantly…how do people figure out what their outdoor targets should be? I just installed a 4iiii power meter. How should I set what my outdoor FTP should be on this power meter? Only ever had power on the wahoo kickr.

Not necessarily…your L/R balance is not static and varies across time and even a given workout, depending on what you are doing. So during endurance rides, you L/R balance may be 50.5 / 49.5, but during threshold work, it could be 52 / 48…and then it could change on a different day.

The challenge is that you never know…

That said, a single-sided power meter is better than no power meter…they are a great choice for many people.

True, but as I said and was the overall thrust of my post, that 1-2% difference falls within the accuracy of the power meter in the first place, so it is splitting hairs. As a dual-sided PM owner myself, I will again state my opinion that a dual-sided power meter is the most luxurious of luxuries for all but a few cases, and I will personally never waste the money on dual-sided again. YMMV.

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You could run a TR workout that has you do various efforts across power ranges, record the Kickr on Trainer Road, and record the 4iiii output with your head unit. Compare the data between the two and you’ll get an idea of the variation between the PM and your Kickr at various power outputs.

Better still, conduct an FTP test on your trainer using the 4iiii as your input (via PowerMatch), and train indoors and outdoors with that FTP direct from your PM. This is definitely the preferred method, as any time you change power measuring devices you should re-test.

Yea that is what I was thinking.

Only catch is that I have a dedicated trainer bike, that has a square taper bottom bracket. PM is on my focus cross bike, which has a goofy through axle system that is incompatible with trainers. I guess I could stop cheaping out and spring for a $60 trainer axle for it…

See your points but you’re way over stating those 99% numbers. The variance isn’t consistent either as people move through the zones. May not make difference to you but it’s more than 1% of people that see these issues.

I think that $60 investment would be worthwhile, IMO! Let you put the bike you ride outdoors on the trainer and remove all doubt!

Maybe 99% is an overstatement, but as others alluded to, it varies for everyone ride to ride and varies at different efforts. The portion of the cycling population that sees a consistent 55/45 difference between their legs is very, very small, and I would feel safe in saying that the % of people who think they really need a dual-sided power meter is a heck of a lot bigger than the % of people who actually gain any benefit from having it.

In the end, we’re talking about a difference of a few hundred bucks in a fairly rare investment in a sport where people routinely spend several thousand to tens of thousands every year on equipment, nutrition, and clothing, so it’s not that big of a deal.

Yea. It just seems kinda silly because it would really only be to calibrate and get an idea of how they compare to each other.

Still, I suppose I would like to know. From a little two mile spin… I have a feeling my wahoo reads much lower. With the 4iiii…sweet spot power felt like endurance, endurance power felt like recovery. I think there might be a 30-40 watt difference.

Or the difference in your numbers just became 2-4% (1-2% for your L/R PLUS 1-2% for your accuracy)…and that is assuming your L/R balance falls into a 1-2% range. I have had rides that came in near 53 / 47.

Again, I’m not saying don’t get a single-sided PM…but the situation is a bit more complex than just saying “it is only 1-2% difference”. For many people, a single-sided PM is a great option…as long as you understand the limitations.

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Maybe. There’s also a pretty marked RPE difference for most folks between indoors and outdoors. My Vector 3 and Kickr are only about 10W different at Sweet Spot and higher efforts, and track very closely below 200W… but when I go do a Sweet Spot effort outside it feels much easier than on the trainer even though I’m using the same power source!

In any event, have fun with it! A PM is a great investment, no matter which way you choose to go.

I’m in no way saying there aren’t limitations to the data provided by single-sided. My argument is based on the utility of the information given by a single- vs. dual-sided PM. You know you come back 53/47. I’ve had rides come back 55/45 before… The question is, what do you do with that knowledge when, as you said, it changes ride to ride, isn’t consistent based on anything you can control. My opinion here is just that there are much better ways to spend a few hundred bucks, but I don’t fault anyone that goes dual… I did. It’s just money I wish I had back. :slight_smile: