4iiii Dual Sided Power Meter: A Short Test Ride


Last Friday while on the way to the airport from Kananaskis (in the mountains for the ANT+ Symposium) to Calgary I swung by the 4iiii headquarters in Cochrane.  The time I had was rather limited, as I was super time-boxed with daylight on one side, and a flight departure time on the other.  But, it gave me a chance to try out their work in progress dual sided 4iiii power meter.

You’ll remember they announced the unit about a year ago at Interbike, but only started shipping their single-sided unit earlier this year.  The dual-sided unit has continued to be worked away on by engineers as they concurrently worked through various teething items on their single-sided unit.  Of course, virtually all of those since-released updates apply to the dual sided system, so it’s certainly not time lost.  You might remember I encountered some issues with their single-sided system, and basically had to wait there for them to resolve some items.  They handed over a new left crank arm to me on Friday, which should resolve the issues I saw, and I’ll install when I get back from my current trip.

As for the dual-sided unit, you’ll notice things have changed a fair bit in terms of looks on the above drive-side, with the battery pod becoming a fair bit more accessible now.  You can just see the top edge of the backplate if you look directly above the crank equal to where the 4iiii Precision pod sits now, in front of small chainring.

A Ride:


As noted, I didn’t have a ton of time during the ride.  The bike was ready to go, but we had to pair up my head units.  Due to apparently none of us being fully awake, we didn’t quite realize we were pairing to the wrong thing – so we sat there burning a solid amount of time trying to figure out why on earth calibration wasn’t responding as we’d expect.  Apparently we had had written down the wrong ANT+ ID from another device nearby.  Eventually though, the four of us (ok, maybe more of us at that point) got it all set and headed on out.  Unfortunately, that did cut into some of the ride time.


The ride was a simple out and back.  We had wanted about 45-60 minutes to ride, but with everything that ended up being about 30 minutes (and even that I got some unhappy looks at the airport check-in desk).  Still, enough to establish a basic level of functionality.  But of course nothing that would count as a review.

We headed out on a gradual climb, and then came back downhill with the wind.  We threw in a few sprints for the fun of it, and otherwise took turns on the way out going into the wind.


Once we got back, I snapped a few quick photos of the bike – which happened to be well known engineer Keith Wakeham’s bike (seen below a bit further).  It had his PowerTap wheel (hub) on it and the 4iiii Precision (dual) system, and then I stuck on my PowerTap P1 pedals.  Normally I’d have preferred to at least get about 10-15 minutes of settling in any new installation, but I made due here given the time constraints.  I did a few quick sprints around the parking lot and called it done prior to the ride.

Afterwards, I downloaded all the data (which I recorded on my head units) and threw it in the analyzer to see how it faired (shown with 30s smoothed average below):


Overall, pretty good.  The three units tracked fairly closely throughout the entire ride, and the ‘ordering’ was proper.  By that I meant that the P1’s registered the highest, and the PowerTap hub the lowest, and the 4iiii Precision smack in the middle.  This is how it should be, since the highest power output would be closest to your legs, and then would be slightly lower as you get further from your legs (due to drivetrain/etc losses).

One might make the argument that the spread between the P1 pedals and G3 hub was a bit more than I’d like to see – but things seemed to settle about 20 minutes into the ride, which would be somewhat logical given I just had installed them.  So I’m not at all concerned there.  And anyway, the Precision sat in between those two lines – which is really what counts.

As for cadence, the P1 and 4iiii Precision agreed quite well.  There’s only a few seconds you see where they disagree, and that’s more than likely to do with just the way units stop/start as you’ll notice they are all at points where I otherwise stopped pedaling briefly.  That’s pretty common.  I didn’t include the PowerTap hub cadence in this graph because I find that in comparison graphs it ends up being funky during stops/starts because it’s an estimation more than anything.


Oh, and finally, here’s the Mean/Max power graph for the three of them:


Again, ordered the correct way, though the P1’s are showing a tiny bit higher here –but again, it’s probably taking those first 10-15 minutes to settle out after install.

Going Forward:


So what’s the plan going forward for getting these into your (or even my) hands?  Well they’re being a bit shy on details until they’ve got things more concrete.  Right now the official line is that they’ll start shipping “In Early 2016”, so that’s about the best we’ve got date-wise.

They said that as they near that timeframe they’ll reach out to those that have pre-orders for the dual system and get them all squared away.  Until then, I expect they’ll basically be quietly working away on it.

With that – thanks for reading and have a great weekend!


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  1. jason

    Was the fix you needed hardware or software related/what’s the plan for those of us that already have the left?

    • Jason,
      In Ray’s particular case, he saw an under reporting of power due to an unusual pedaling style. In addition to ongoing design improvements to PRECISION, a firmware update addressing the issues that Ray saw with his crank will be available to all PRECISION users in the next few weeks.

      As a bit of background, the majority of people pedal in a generally circular motion and receive accurate PRECISION values. For most of us, the crank arm and pedal cause our legs to travel in circles, but a small percentage of cyclists exert unusual forces on the pedals. This is what was happening with Ray. Anyone exhibiting an unusual pedaling style and wanting to compare power data with other meters, will benefit by the firmware upgrade. It should be mentioned that for those who only use power-based training plans, unusual pedaling style is of no consequence because PRECISION measurements are consistent and relative from day to day.

    • Ross

      Ray, tell us some more about your ‘unusual pedalling’ style!?

      How does this manifest on the Pioneer which has a polar type analysis of your pedal stroke?

    • Alex

      With regards to accuracy vs consistency it’s worth referring to Ray’s previous thoughts here:

      link to dcrainmaker.com

    • Ross – I assume that by time you typed the comment Chris from 4iiii looks to have already responded (he’d honestly know my apparent pedaling quirks better than me).

      As for other power meters, I haven’t seen it surface anywhere else – either in comparisons or data analysis pieces like what Polar, Garmin, and Pioneer offer.

    • Josip

      Would be interesting to get a bit more info on this issue. “Unusual” is a bit vague and not very helpful to understand what is going on.
      “the crank arm and pedal cause our legs to travel in circles” is also nothing more but stating the obvious, imho.

      Also, will the firmware update fix the issue completely?

    • We understand Ray’s quirks – things like Left/Right imbalance, pronation on the pedal (EG: turning your foot in the bracket), leaning on the inside or outside of the pedal and numerous other forces and torques applied. The precision powermeter is unique in that it understands more than just simple bending with an approximate calibration. A real crank arm cannot be accurately approximated by this method for true torque sensing. Further refinement to the build process rectified an issue affecting a limited number of crank models for a small percentage of riding styles. It has been our very unfortunate learning experience that the crank model sent to Ray combined with his style was in that category. Only one person of all the 4iiii’s personnel has been able to present with similar magnitude of error. For those who people who are used to training with another device, that measures in another way, we are pushing an update that deals with these nuances by a user Scale Factor which adjusts the multiple calibration values internally.

    • The old, outdated advice for pedaling is to pedal circles. The new advice is to have a more piston or vertically applied pedal stroke. This is the way I pedal and the way I coach my cyclists to pedal. It eliminates quad fatigue by making it easier for the glutes to activate. Rather than pushing and pulling, there’s a power phase and a recovery phase. Power is only applied during the downstroke. For this pedaling style, will it be able to accurate measure power?

  2. tim

    thanks for the the photos making my home province look good

  3. Matthew

    Very cool. Any idea on price they may be shooting for?

    • My understanding is the pricing remains unchanged from previously announced – so $749USD for the dual system.

    • The target MSRP for dual sided PRECISION of $749.99 was introduced last year. This price is being reviewed and pricing information will be relaunched with the upcoming Dual PRECISION announcement.

    • Andrew

      It would be helpful to know the ball park as I am thinking about buying the the single side only for now, with the goal of upgrading to dual side later. And with other products out there at a similar price point, the ambiguity in pricing makes it hard to pull the trigger on the single side now. Thanks!

  4. Karl Nelson

    What losses are there between the pedals and crank arms? Pedal bearing friction? Is that so significant that you would expect to see a difference in power between the two locations?

  5. Dirk

    I ordered the dual and had the left installed already. I am assuming the dual will have the same left sided pod. Is this correct?

  6. efrain

    So does this mean that 4iii will not do the dual sided power meter with their pods?

    • The post is about a dual system, so it’s all about dual. What Karel was referring to is that the pods are now different between left and right. You can see for example that the right side (drive side) has a different battery-accessible compartment meant to make it easier to remove the battery from behind the chainrings/spider. Whereas the left-side looks basically like a little footpod.

  7. Mickey

    Any comparison between the single and the dual 4iii solution any time soon? I’d be interested to know the real-world comparison showing the potential discrepancies. Come to think of it, I’m not sure I remember such comparisons for Vector, Rotor, or any of the other manufacturers offering both options. I’d bet that published variations of note might spur Stages to re-consider the single-only product.

    • I did show some of those differences in my Stages post (really the only one-legged option I’ve deeply reviewed). I’m looking to put together a bigger post probably in late November on the challenges of left-only.

      Some folks have actually dug through my data to show some of those left-only issues.

  8. Todd

    I want to mention that I was an early purchaser of the left side Precision power meter. I had similar issues apparently that Ray had. I needed to sort my power meter out so I ended up moving on. That being said, 4iiii and Karel gave me excellent customer support. I would not hesitate to recommend them to anyone looking at purchasing their products!

  9. Jason

    Ray, do you know if there will be a right side-only option (not dual)? Your post is all about dual.

    I first ordered the left side model but found there wasn’t enough clearance between my crank arm and chainstay-mounted rear brake for the pod, so I’ve been waiting for the right side model to be released.

  10. Stefan

    Will the new dual design work for more compact crankset designs? Seeing the picture above I don’t think this would work for MTB. This could have been the first real dual side PM for MTBs.

  11. Ricky

    And is this one carbon compatible ?

  12. Fred2

    I imagine there is still a strain sensor on the back of the crank, but probably much thinner than when combined with all of the electronics, as earlier. I’m curious what it looks like back there, but expect that 4iiii isn’t ready to reveal its final design, yet.

  13. BruceW

    Do you have more photos of what the pod looks like on the reverse of the crank arm (drive side)? Has the non-drive side pod changed design – photos if you have them?

  14. John

    Maybe I just missed this, but what is the installation configuration on this dual sided version? Pre installed crank sets? Self install? Factory install on existing crank sets (including shipping both ways)?

  15. HA

    Can the single sided precision be upgraded to dual sided powermeter or is this a completely new unit? If the precision can be upgraded to a dual sided powermeter, will 4iiii provide a chance for its existing precision customers to upgrade to dual sided if they want to? Appreciate your thoughts.


  16. Adam

    If I buy the dual sided package and use it on my roadbike, will I be able to move the left crank arm over to my cyclo cross and use it there as a left-only power meter? Or will the two pods only work in conjunction with each other if configured that way?

    • Ted

      I too would be interested to know whether the left arm from a dual-side setup can be used alone as a single-sided power meter on another bike.

  17. Allan

    What I still haven’t seen an answer to is do we need to know if our pedaling style is “unusual”? Like, if I complete the firmware upgrade does that forever change the way Precision calculates power readings? If my pedaling style is circular or otherwise, will power numbers be the same after the update? Basically, if my pedaling style is not ” unusual “, does that mean I should not do the update since the calculation algorithm had been changed to compensate for the unusual style?

    • I don’t think you’ve seen an answer there because they don’t have a good answer. In theory, if your pedaling style falls into a different category, then yes, your numbers would change. Which is obviously a challenge.

    • Allan

      Hey thanks for the reply. I’m still not sure if I’m asking the right question, but if this firmware update is aimed at correcting for an “unusual” pedaling style, will the power readings change, even if my style is not “unusual”? What I don’t want is the power readings to be even more inaccurate after the update, if the way the PM calculates power is “updated” to reflect different pedaling styles.

      I don’t know if my style is unusual, but I am almost certain this PM reads low. Regardless of whether or not that matters, so long as it is repeatable, it would be nice if a power meter actually gave us accurate numbers. Based on many different factors, I feel my Precision is at least 15% low. At this point, I’d rather just have a simple scale factor applied to what I am observing and have compared to, even if it seems completely random.

      I hope you get a chance to review the single sided Precision with comparisons to other meters soon, especially after the update.

    • Allan

      Man, I just re-read my reply, and I’m confusing myself! I’ll have to shoot an email to 4iiii, and try to get my thoughts together properly!!!

    • Iain Gray

      From what I gathered from correspondence with 4iiii it will be a scale factor. Myself I have a 16% low reading with only 6% accountable from a leg bias.

  18. Michele

    How does temperature affect the performance of the Precision? How does it fare in wet conditions?

    • Dolan Halbrook

      I swapped mine from my race bike to my rain bike a few weeks ago. This past week alone, Portland has gotten nearly 3 inches of rain, so needless to say, it’s been really really wet. Today my Precision stopped working halfway through a rainy lunch ride, and my first thought was that it had leaked and shorted out.

      When I got home and opened the battery compartment, I noticed a tiny bit on condensation on the battery (as a result of bringing a cold thing into a hot place), but otherwise it was 100% dry. Popped in a fresh CR2032, fired up the Garmin, and sure enough it was ready to roll again.

      So is it waterproof? Close enough for me.

  19. Matthew Neugebauer

    Guess the folks over at 4iiii feel like their dual sided system is ready for the big leagues!

    link to 4iiii.com

  20. Astolfo

    So I am just about to buy a pair of Vector-2s but I would love your advice, what power pedals you think should I get.
    Thank you!!!

  21. Simon

    Any whispers of this being available yet? I’m getting impatient and P2M is looking more and more tempting…

    • No, I think they’re a bit further away than closer.

    • Simon

      Thanks! What are your thoughts on how much longer 5 bolt chainrings will be around for? Shimano, Campag and FSA all use them now but Quarq and P2M don’t make 4 bolt PMs yet and I don’t want to go shelling out £600+ and find I’m struggling to find replacement rings a few years down the line…

  22. Jonathan

    Just curious to know if the installed PM on the right side will still allow you to swap rings out. If you wanted to throw on a compact set for a weekend in Colorado, could you easily swap them out, or will the installed right side unit cause clearance issues?

  23. Vitaliy Uvakin

    Any chances pm could be self installed?

  24. Alex

    Hi Ray,
    I was wondering if you knew about any updates for shipping the dual sided power meter. The end of the article states shipping early 2016 but we are way past that. it seems they are having some issues consistently delivering their single sides unit so I’m guessing this has delayed them quite a bit.

    • Mike S

      The website says that the duals are now shipping!!

    • Nate

      I sent them a question last week about buying the dual system. It seems they will only install the dual system on the dura ace crank/chainring currently, though they will install the left-handed meter on my ultegra left crank.

      They said I could purchase the dual system now and have the left crank installed and wait to send in my right ultegra crank when they start installing the dual system on that but no indication of a timeline was the sad news for me. I can’t justify the price difference for a dura ace crank when I have two good current model ultegra ones…