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.
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.
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.
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.
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.
This was why I originally went dual-sided. I have about two years of L/R data now, and while its interesting, nothing for me is actionable, and I’m to the point where until today I hadn’t even bothered to look at it for probably six months. Hence my stance for the “99 percent” (which is probably overstated!).
No regrets going single sided here. I guess the only downside would be if you are trying to do single leg drills on the trainer in erg mode with powermatch it could get interesting. I don’t do single leg drills as I think they are useless so it never bothered me.
I did buy a Power2Max so I could asses L/R balance after learning about some physical asymmetries (leg length, lateral pelvic tilt) during a several month long bike fitting process. After looking at the L/R data for 2-3 weeks and seeing there were no huge differences I haven’t seen any benefit from having dual sided power.
Most likely, yeah…there have not been any studies saying that a 50/50 balance is beneficial or provides any benefit. As noted, it varies day-to-day and even within a given ride.
Just to clear up my points above, I was not referring to being able to even out your balance, just noting that w/ a single-sided PM, your FTP, or your training zones on a given day, could be off by as much as 4% (if not more). That can make a big difference at higher intensities.
Thanks to this thread, I went back and looked through my power files for the last few months… worst day was 53.3/46.7, and on my most recent 2+ hour outdoor ride I was 50.1/49.9. There’s no rhyme or reason for it that I could discern; some easy rides I’m right near 50/50, but some hard rides I’m less than 0.5% different… The other thing I’d point out is that one wacky reading or power spike can render these numbers meaningless, and unless you go in and cut out specific spikes to make your numbers proper if that happens, you could be operating under false info.
This is just my opinion as a coach and long-time athlete, and there will be dissenting opinions out there, but unless you are recovering from a serious injury or have a life-long issue with different leg lengths or strength mismatches, you’re probably wasting your time focusing on trying to get 50/50. Even if you know you have a marked difference, there’s not much you’re going to be able to do about it on the bike.
I dislocated my right foot playing basketball a number of years ago, and I had a strength mismatch between legs for about 12 months. That was resolved through PT and weight lifting focused on single leg/calf strength exercises. If you’re convinced you have a strength mismatch, that’s the way I would go (Pistol squats, single leg calf raises/extensions, single-leg presses, etc.).
As mentioned, when I first got my dual-sided Vectors, I looked at it all the time. Now, I never look at it, and the most value it provides me any more is to remind me when I’ve forgotten to link my right pedal to the left after I change the batteries!
Won’t it be need a road PM though (105) because of the different q factor on the MTB (XT) cranks?
FWIW I’ve got 105 Stages single sided with DA cranks. Have never, ever worried about L/R imbalances, because what I am going to about correcting the imbalance?
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.
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.
