Shimano Based Crankset Power Meters: Not As Accurate As You Might Think

This report presents clear evidence, based on robust data, that power readings derived from dual sided cycling power meters using Shimano cranks, does not provide consistent levels of accuracy as specified by power meter manufacturers.

The Shimano alloy crankset is a popular base unit for a number of companies to use for their power meter products. Not originally designed as a power meter, electronics engineers successfully mounted strain gauges on the left side crank only (where power was doubled) to give cyclists a more cost effective way of measuring their power output.

Stages Cycling was the first company to develop left-crank based power, applying strain gauges to the crank arm. Stages Cycling – Wikipedia 

Following the success of Shimano based left-only power meter products almost every company started offering a dual sided power meter configuration by placing strain gauges on the corresponding right side crank arm.

From a consumer perspective this was welcomed. A somewhat cost effective (“somewhat” as it’s not as cheap as a left-only offering) dual sided power meter, independently measuring left and right power, and reporting metrics such as pedal balance and true total power output. 

From an engineering perspective the right side Shimano crank power meter has been a challenge. The design and shape of the right crank is very different from the left, and with Shimano changing the shape from the FC6800/FC7900 with the R8000 and R9100 right side cranks for a wider four arm arm/spider interface, things became even more challenging for them to obtain accurate power (torque) measurements from. There has been mention of a strain gauge redesign required specifically for the R8000 & R9100 right side cranks.

Over the past year I’ve ridden and compared power readings from ELEVEN (11) Shimano R8000/R9100 cranksets from seven companies. I’ve had other riders perform the same testing protocols on a number of these units. Based on the data from these tests, and confirmation of these results from independent electronic engineers who are familiar with cycling power meters – I do not believe the power measurement from any Shimano R8000 or R9100 RIGHT side cranks is at an acceptable level for consumers to confidently rely on at this point in time.


I have been in direct communication with a number of the companies mentioned in this report over the last 12 months.

None of these companies have questioned my testing protocol, or results for what would be considered successful tests of left-only power meters and their non Shimano dual sided power meters.

Each company has been provided this report and all data collected on thier power meters in advance for response.   

My goal here is to identify issues consumers may encounter themselves with these products. I hope these findings will lead to more accurate power meters on the market.



Strain gauges are a solved problem. The gauges used today are reliable and dependable. Other power meter features are of a high standard: Battery life. ANT+ & Bluetooth Smart data transmission. Active Temperature Compensation (to an extent). If this wasn’t the case the power meter industry would be in trouble.
Digital cadence sensors are also typically accurate enough to obtain quality power output from. (Accurate cadence is required for accurate power from these power meters). Some power meters still rely on magnets for better cadence readings (which are more responsive in my experience). Accurate cadence readings are a part of this bigger picture discussion, but they’re not the main show in this report.

Why are power meters so hard to get right? 

Bicycle power meters are effectively a moving weight scale. Standing on a bathroom weight scale requires you to be stationary for accurate results. Power meters require the same accuracy moving at high speed (rotation, vibrations, etc), while measuring multiple force vectors, in almost all environmental conditions imaginable.


Shimano Cranksets as Power Meters

Shimano produce cranksets, not power meters. Converting these cranksets into power meters is a post-production process where strain gauges are typically placed on the external surface of the crank arms.

Shimano use the same post-production strain gauge placement design as third parties for their DuraAce R9100P Power Meter. However when Shimano themselves can’t produce a quality industry leading power meter from their own cranks from day one – there’s a problem. A big problem. 

– DCRainmaker DA9100P Review: Issues with left/right accuracy.
– Bike Radar DA9100P Review (Ben Delaney): Issues with left/right accuracy.
– GPLama DA9100P Review : Issues with left/right accuracy.

Discussions with a power meter designer/engineer Keith Wakeham on the topic of using Shimano cranksets as power meters has confirmed there are difficulties with design asymmetry, chainring positional affinity, and the coupling effect when using strain gauges on the RIGHT side crank arm of a Shimano crank. This is a known problem that isn’t limited to just the drive side, however it’s where the issues arise when using a DUAL sided Shimano based power meter.

Inside Shimano HOLLOWTECH Cranks

Internals of a FC-R6800 RIGHT Hollowtech crank.
Photo Source:


Internals of a FC-9000 RIGHT Hollowtech crank.
Photo Source:


Onto the testing…

The Lama Lab Test Protocol: 

My “Lama Lab” test protocol has shown to provide quality results when testing both power meter and smart trainer power measurement. It’s by all means not perfect, however it has successfully identified issues that have been acknowledged (and in some cases resolved) by power meter and smart trainer manufacturers.

This protocol uses a combination of SIM (Simulation) and ERG mode. ERG mode forces you to pedal at the set target wattage. For more details on ERG mode I have a 12 minute video explaining ERG over YouTube: ERG Mode Explained.

– Power meters stationary in the room for at least 10 minutes (temperature adjustment)
– Data recording on Garmin Edge or Wahoo Elemnt units (using the same vendor for all meters if possible). 
– 1 second record interval. GPS disabled. Units placed <1m from power source.
– Clean chain (<0.75% wear). Clean Cassette.
– Straight Chainline selected (36/39 17-18) for ERG.
– Zero-offset performed on all units (as applicable) at 0 minutes.
– 10 minute ride (SIM mode / Human warm-up / a few short hard efforts).
– Dismount bike. Zero-offset performed on all units / Spindown on trainer (if applicable).
– 10 minute steady-state ERG @200W ~88-95rpm. Both hands on bars. Natural/smooth pedalling. 
– 10 minute steady-state ERG @250W ~88-95rpm. As above. Balanced, smooth, natural pedalling.
– Maximal sprint of 5-8sec. Out of saddle.  (SIM or Level mode).
– 4 minutes easy spin (SIM or Level mode). 
– Over/Under Intervals in ERG each of 20 seconds: 150W/350W/150W/350W/150W/450W/150W/450W/150W. Balanced, smooth, natural pedalling through these intervals. 
– Cool-down. Sometimes involving a harder 350W/400W effort for ~60 seconds in SIM to collect more data. 
– All data (FIT format) labelled according to equipment used and uploaded to DCR Analyser.

Shimano Based Power Meter Cranks: LEFT ONLY

Data shows left-only Shimano based power meter cranks typically report power within their specified accuracy specification (+/-%).  I have encountered some left side cranks reporting lower than expected power measurements. In some instances this has been resolved with re-installation and correct torque on the pinch bolds (14Nm – max specified by Shimano). I have had left-only cranks from manufacturers not listed in this report that have zero-offset stabilisation issues and power fluctuations. So they’re not immune to issues either.

The caveat with LEFT only is with the doubling of power from one side. It assumes 50/50 balance for the unit to show “correct” output. Small lag in power reporting due to no measurement on right side. 

In short – Data collected on LEFT only Shimano crank power meters appears mostly accurate. This report focuses on the RIGHT side crank arm.

Stages Power Meter (Single/Gen III) – Install, Ride, Data Review
Magene RIDGE Shimano Ultegra R8000 Power Meter: Details // Install // Data Review
XCadey X-Power Budget Power Meter: Unboxing, Install, Review


Shimano Based Power Meter Cranks: RIGHT / DUAL SIDED

Here’s where things get tricky.

Shimano Cranks Tested (11):  

– Stages LR (x2) 
DuraAce R9100 (Gen 3) 1st Unit
DuraAce R9100 (Gen 3) 2nd Unit

– Pioneer (x3)
DuraAce R9100 (SGY-PM910H ANT+ only model) 
DuraAce R9100 (SGY-PM930H ANT+/BLE model) 1st Unit
DuraAce R9100 (SGY-PM930H ANT+/BLE model) 2nd Unit

– 4iiii (x2)
DuraAce R9100 (PRECISION PRO) 
Ultegra R8000 (PRECISION PRO)

– Giant 
Ultegra R8000 (Power Pro MY19) 

– Shimano 
DuraAce R9100-P 

– WatTeam PowerBeat
Ultegra R8000 G3 (*Gauge placement different to the others) 

– XCadey 2XPower
Ultegra R8000

Lama Lab Test as documented above and here: GPLama How To: Comparing Power Meters // Power Accuracy Testing // DCR Analyzer Tool:

The Results: 

Steady-State 250W ERG  

Power Meter: Crankset used
ERG: 50% of 250W ERG Mode (125W)
Other: Right side power channel of non Shimano Crank (Assioma/P1/Vector3)
Right: Shimano RIGHT side reading

Power Meter ERG Other Diff % RIGHT Diff %
Stages RIGHT DuraAce R9100 (Gen 3) 1st 125 124.14 -0.69 116.74 -6.61
Stages RIGHT DuraAce R9100 (Gen 3) 2nd 125 121.04 -3.17 116.16 -7.07
Pioneer RIGHT DuraAce R9100 (SGY-PM910H) 125 123.09 -1.53 112.6 -9.92
Pioneer RIGHT DuraAce R9100 (SGY-PM930H) 1st 125 127.87 2.30 114.76 -8.19
Pioneer RIGHT DuraAce R9100 (SGY-PM930H) 2nd 125 122.79 -1.77 116.91 -6.47
4iiii DuraAce RIGHT R9100 (PRECISION PRO (Dr.SLane Data)) 125 123.18 -1.46 114.44 -8.45
4iiii DuraAce RIGHT R9100 (PRECISION PRO ) 125 123.15 -1.48 114.16 -8.67
4iiii Ultegra RIGHT R8000 (PRECISION PRO) 125 123.36 -1.31 113.95 -8.84
WatTeam R8000 G3 RIGHT 125 124.06 -0.75 117.71 -5.83
Shimano DuraAce RIGHT R9100-P 125 125.67 0.54 115.12 -7.90
Giant Ultegra RIGHT R8000 (Power Pro MY19) 125 122.83 -1.74 120.27 -3.78
XCadey 2XPower R8000 125 125.31 0.25 109.44 -12.45
Average 125W 123.74W 0.90% 115.19W 7.85%

– Variance higher at 350W & 450W ERG.

– Differences not as pronounced in random terrain SIM mode or riding outside. 

– Harder steady-state efforts indoors (SIM) and outdoors does reproduce this issue. 


Isn’t this just drivetrain loss?

No. The discrepancy in power readings is between the pedal power meter and crank power meter which are directly connected. The power differences reported are more apparent on the RIGHT side. The controlling smart trainer in ERG also provides a tertiary power comparison source.


What did I compare against? 

Multiple sources:
– Favero Assioma DUO (Dual sided pedal power meter. ±1% Accuracy) 
– PowerTap P1 & P2  (Dual sided pedal power meter ± 1.5%) 
– Garmin Vector 3  (Dual sided pedal power meter ±1% Accuracy) 
– Tacx Neo / Neo 2 (Direct Drive Smart Trainers ±1% Accuracy) 
– Wahoo Kickr / Kickr CORE (Direct Drive Smart Trainers ±2% Accuracy) 

Basic Formula:
Dual Sided Power Meter L + R = Smart Trainer Power ≠  Shimano Crank Power Meter Total Power.

eg. AssiomaDUO Power = Tacx Neo Power ≠ Shimano Crank Power. 

More specifically indoors and out: Power Meter R ≠ Shimano Right Crank Power.

Note: This doesn’t factor in any specific mechanical losses incurred between the pedal and crank, and drivetrain losses at the smart trainer power measurement point (effectively the rear hub). However, measured losses are never greater than a few watts (<2%) of TOTAL power using a clean drivetrain when cross-chaining using 52/28. Reported power from the RIGHT cranks is up to 10% different, on one side alone.

I can not attribute the differences recorded to mechanical or drivetrain losses.

Why hasn’t this been detected / reported / resolved? 

Comparative testing of consumer power meters isn’t commonly performed. Not typically to the level of detail (and cost) that it has taken me to reach my current conclusions. 

The independent testing of Shimano R9100 LR cranks at the University of Colorado Boulder commissioned by 4iiii on three of their cranks was based on a steady-state riding protocol on a treadmill (not ERG). With their comparison being calculated wattage, not other power meters, and using two minute intervals at lower cadence ranges than I would expect a trained cyclist to ride (only up to 85rpm). Their summary result of 1.58% accuracy was an average across all data sets with the three Shimano R9100 cranks tested.

There was datapoint at ~250W (calculated) reporting as ~240W. Indicating there is outlying data points. 240W @250W calculated is -3.70% equating to -9.7W. What wasn’t reported was the Left/Right power figures on any of these data sets. Yes, I’m being selective here – my point being we need to know more detail as to why that data was out by that much.

On the upside to the testing in Boulder, their results with non Shimano cranks using their strain gauge technology were a LOT better. With the carbon SRAM XX1 crank achieving 0.84% accuracy on average across four cranks tested. Indicating the gauges and technology used by 4iiii is of a high standard that will produce accurate measurements assuming the base crank it is installed on doesn’t suffer from the same problems as the Shimano RIGHT crank design.

Performing the Lama Lab Test protocol on the dual sided FSA SL-K crankset fitted with 4iiii power meter gauges reported no issue with left or right side power readings.

Why haven’t other media and reviewers reported this?

I’ve not seen any reports showing the same testing as what I use in the Lama Lab (as documented above). Specifically longer duration smooth pedalling steady-state ERG efforts in addition to over/under intervals – Tested against a long-term known-good power sources – Which I consider the AssiomaDUO / Tacx NEO / PowerTap P1 to be.

I have discussed this issue in a number of reviews already. In particular the Shimano R9100P, my WatTeam G3 review (results confirmed by WatTeam engineers), and in my Stages LR video. This isn’t ‘new’ news.  

This is also difficult to diagnose. It requires multiple power measurements on the same bike at the same time. Not many cyclists will install two independent L/R power meters on their bike. Even less will perform any in-depth analysis of the data. A growing number of cyclists are comparing their bike power meters to their smart trainers and are reporting power differences. This issue could very well provide answers to some of those queries.

More often than not when users ask questions regarding power meter discrepancies in a public forum they are dismissed as ‘drivetrain loss’ or L/R imbalances. Unfortunately these reasons are echoed by some manufacturers without performing a full analysis of each issue. This is not a drivetrain or a rider L/R imbalance issue.

What exactly is the issue and why hasn’t this been resolved in firmware, or with better strain gauges?

The engineering complexities of this problem is best explained by someone who can cover this in the technical detail it deserves. And that person is Keith Wakeham. Keith is one of the original designers of the 4iiii power meters. Keith is listed on the patent under ‘Inventor’. He really knows his stuff. Reference:

Keith has a blog over on and has put together a post on this very topic:

If you have a few minutes to keep diving into this issue to the depths you never thought possible – Grab yourself a coffee and watch his video here:

This isn’t an incorrect slope or miscalibration issue. It’s much deeper and harder to solve given the design of the Shimano RIGHT crank arm/spider

For now this issue exists even with the latest meters with the latest firmware.


Team Sky / Pro Team X / Mine Reads Fine

Professional teams are sometimes provided non commercially available product. Teams are paid to use equipment (read between the lines here of what they’ll say about said product). Professional teams are also unlikely to perform any power comparison tests to the level required.

“Mine is accurate”. Compared to….? What was your testing protocol? How was the data recorded and analysed? The answer here is typically “we’ll need more data”. Beware. Getting to the answer is a rabbit hole of indeterminate depth.

My Take Outs….

Shimano based dual sided power meters report lower total power in my tests due to inaccurate measurement of power on the right side in a number of pedalling scenarios. This is particularly evident in steady-state smooth pedalling efforts across a range of wattages.

At this point I am not confident to use ANY Shimano based dual sided power meter crankset as a baseline to compare power readings from other power meters or smart trainers.

I own a Shimano based dual sided power meter as referenced above. Does this matter? 

– If you’re using the reported L/R balance values as part of your training.
– If you’re comparing multiple power sources.
– If you have more than one type of power meter (One that’s Shimano based, and one that is not).

– You’re not bothered with L/R balance. 
– The power meter is your ONE source of power for all training.
– You have more than one of these Shimano crankset power meters.
– You’re not worried about a few % margin of error with your real power output (and metrics that are slightly skewed because of this) 

Company Responses… and where to from here.

All in all I’ve welcomed the discussion this report has lead to with most of the companies named. There is obvious (and admitted) complexities with the Shimano RIGHT crank design when used as a power meter. 

I understand it’s not in the interests for any of these companies to admit any major shortcomings of their products. What I’m looking for is a sound explanation as to why these discrepancies have been narrowed down specifically to Shimano RIGHT cranks – why I’m not able to use any of them as a reliable baseline of power comparisons – and most importantly – is there a possible fix for this?

Shimano Australia:
– Stand behind their ±2% accuracy claims of LEFT and RIGHT Shimano Power Cranks.
– Discrepancies in my provided RIGHT power data due to bugs in the firmware I used.
– I tested the R9100-P with 4.0.7 (March 2018) which is the firmware that their changelog indicates resolves accuracy issues.
– It was recommended I update to 4.1.7 (Feb 2019) and retest.
– I raised concerns that 4.1.7 change log lists no updates to power accuracy. Also infers they had an inaccurate power meter on the market up until February 2019…!?

My Action Points: Source another R9100-P and retest with 4.1.7.

4iiii Innovations: 
– Acknowledged issues with the Shimano crank asymmetry and non-uniform coupling effects.
– They believe their firmware and calibration protocols are robust enough to stand by their accuracy claims. 
– My riding style given as a possible reason for the discrepancies seen in ERG. (This doesn’t explain why my riding style wasn’t a problem with their non Shimino L/R crank in the Lama Lab tests, or Dr. S.Lane also recording the same lower power measurements with the Shimano based RIGHT crank). 

My Action Points: Continue working with 4iiii to provide more data from the Lama Lab and in person across more of their power cranksets (Both Shimano and non Shimano). Ongoing.

Stages Cycling:
– Stages stand behind the accuracy and repeatability of the Stages Power R and Power L/R meters in the vast majority of use.
– They mention the loading of the spider and crank is different during the pedal stroke in ERG as opposed to SIM or riding outside – which could be contributing to the discrepancies. 

My Action Points: Continue working with Stages to provide more data from the Lama Lab and in person across more of their power cranksets (Both Shimano and non Shimano). Ongoing.

– Data analysis still in progress. TBA. 

– No response. TBA.

– No longer in business. RIP.

– Data analysis still in progress. TBA. 



– In comparative power meter testing it is difficult to use the total ride/activity power as a measurement of accuracy due to factors such as start/stop delays across different power meters, possible data interruption (drop outs), etc, all impacting the overall total power recorded. This is why the focus of this report is specifically on 250W ERG steady-state efforts.

– The data from the Giant PowerPro has changed with recent firmware updates. From reading high on the right, to low, to a random point in between, sometimes. I suspect they are fudging or scaling the left/right to account for these issues. The dataset used here indicating LOW readings on the right was from fw237 (latest release as of testing).

DCR Analyser: Online tool for reviewing and comparing FIT file data. 

Shimano R9100-R Power Meter tested June 23rd 2018 with Firmware 4.0.7 released 27th March 2018 – “Update to make output value more accurate”

Technical Report:Accuracy Testing of 4iiii Innovations PRECISIONPowermeter Technology. Scott Cooper, Ph.D, 4iiii Innovations Inc. Wouter Hoogkramer, Ph.D and Rodger Kram, Ph.D, University of Colorado Boulder University of Colorado Boulder Locomotion Lab September 14, 2018

Patent US10060738B2 (United States) Adhesively coupled power-meter for measurement of force, torque, and power and associated methods Inventor: Kipling Fyfe, Keith Wakeham

Validity and Reliability of the PowerTap P1 Pedals Power MeterJ Sports Sci Med. 2018 Jun; 17(2): 305–311.



Shane Miller

92 thoughts on “Shimano Based Crankset Power Meters: Not As Accurate As You Might Think

  1. Brilliant research here mate. This seems like a pretty big issue. If power meters are claimed to be within 2% accuracy and they are upwards of 8% they are open to a large number of returned products.

    I was going to go crank based but not now. Cheers legend

  2. Yep, I’ave always thought the readings from my Shimano 9100 power meter were dodgy, this just confirms my intuition. I used to actually watch the readings on my old power meter but I take the readings on this Shimano Power Meter with a grain of salt.

  3. When did they know and Who knew? Is the question. These companies have been taking advantage of the consumer for years. These companies have been making tens of millions of dollars just hoping you didn’t notice. The companies in question all took part in a Greed campaign instead of facts. The industry has come along way in the past 10 years because of the willingness of dedicated consumers to embrace the science. The consumers and science have pushed the industry to where it is today! Consumers had an option for a better product but because of their cover-ups and misinformation we made a wrong decision. One last thing, when we spend $1,000 on a product. We are investing in you and expect and deserve respect.

  4. Hi Shane, I really enjoyed reading through this article. I’m wondering what’s the effect of this on total power accuracy? From your tests its clear that the right side isn’t measuring accurately. However, many of these units line up well with other power meter types in most of the tests Ray preformed (to the point Ray recommended the units as accurate and reliable). I’m trying to figure out how to interpret the idea that the right side meter is reading inaccurately, yet the total power appears to display within manufacture +/- specs. Is this issue addressable through a firmware update?

    1. Total power is impacted. Total = L + R.

      I address total ride/activity power, other reviews, and the firmware question in the report.

      See Keith Wakeham’s video linked in the report for the engineering ‘why’ of this problem.

      In short – There’s a problem. A big problem.

      1. Fwiw – I’ve actually only reviewed a two units with the impacted crank arms noted here (Stages LR & Shimano’s own solution). The remainder have been other units either prior to this set of crank arms, or just other crank arms or technologies altogether.

        The challenge is the lack of consistency. In my Stages LR test, I actually had pretty good results (and have for a while). Though, I’ve also seen some oddities here and there over the last 4-6 months that don’t make sense in isolation. In the Shimano power meter test, it was a complete mess. Oh, actually technically there was a third – WatTeam G3, which one might remember I saw issues that couldn’t be explained at the time that needed more investigation. Then they went under.

        I am in the midst of testing the latest 4iiii Shimano dual-sided units, and have been seeing some of the issues here. I haven’t completed my review yet though.

        I’ve poked at a few left-only solutions, but as noted those really aren’t super impacted here since the variation is already into the variable category.

  5. My Sigeyi Ax power dual side (Chinese power meter) on Shimano 105 previous generation (5800) do not seem to suffer from right crank low power reading. Perhaps older symmetrical design have no problem but only Chinese power meter make them now.

  6. Thanks for a great investigation. It is completely aligned with my own experience.
    I did a limited investigation myself after getting into real (fatigue) trouble at an early spring training camp in the mountains when I used a Stages LR (Ultegra R8000) for pacing. I had been using my Tacx Neo all fall and winter and it became obvious that it was a big difference in reported power (even more for me as my left leg is weaker due to an injury).

    I resolved my problem by getting a pair of Assioma Duos. My testing suggests that my Tacx Neo and Assioma Duo are within 2 watts at my FTP (270W). My Stages LR reads 18-20W lower at this effort. It looks a bit silly with power meter pedals mounted on a (unused) power meter crankset;-)

    Life would be perfect if Favero could sell a conversion kit to SPD-SL for the Assiomas.

  7. And I just ordered the Stages LR Factory Install at the beginning of June. Bugger…

    If there were more options for pedal based power meters, like SpeedPlay’s, and SPD-SL’s. I already have enough different pedal systems, and really don’t want to add yet another. Can’t some of these companies start being more agnostic, and release pedals with different cleats? It would be such a great thing for people with multiple bikes. COME ON INDUSTRY!!!

  8. GPLama: Three questions, and thank you for this analytical work!
    1. I have a Stages Gen 3 L/R Ultegra 8000 power meter. You don’t mention this solution, but I could disable my right power meter and just go with the left. Yes, it’s only a Left side power meter now, but improved accuracy would be the result, correct?
    2. I show about a 56/44 L/R power discrepancy when I ride. Is this due to the crank effect? FWIW, my Assiomas show about the same L/R discrepancy when I use them on other bikes.
    3. Why couldn’t software updates take care of this problem? I will dig deeper into the structural issues, but those are a static given set of conditions and thus, software should be able to offset the problem. Yes, they should eventually build on a better crank, but is the problem data volatility, or just always being off by a particular percentage? If the latter, companies could tweak the software.
    Thank you!

  9. PS: After watching Keith Wakeham’s video (thanks for link) I see the answer to my third question is no, software updates won’t adequately solve the problem–too many environmental and structural variables. But disabling the right power meter seems like a good interim solution, no?

  10. This is of interest to me:

    Stages Cycling:

    – They mention the loading of the spider and crank is different during the pedal stroke in ERG as opposed to SIM or riding outside – which could be contributing to the discrepancies.

    I recently experienced an oddity when racing in Zwift. I found that my FTP during the race jumped up by 29W. So 246 ERG in my workouts and FTP test, and 275 during the race, relatively flat and I did a lot of hiding. It was enough of a jump that Zwift Power nailed me with a WKG penalty. If this is the new reality how am I suppose to compete even if its just for fun? Is there any guidance you can provide?

    1. Hey Mick. I have 0% claim on testing accuracy but from all my experiences with a Garmin Vector 2 or Assioma, I’m 49% – 51% balanced.

      S-works 4iiii dual sided consistently shows me 46% – 54% or there about so I have my suspicions. It has been very predictable in the total number but the L/R has been weird for sure. I also get a reading on my right when i unclip from it and vice versa. Never a 0% reading even if I don’t pedal.

  11. I will gladly take the % difference versus using the tiny parachutes that the power meter pedals are. There’s a reason why all the top riders are using certain pedals. Assuming the data you use is from one meter and it’s consistent (from the same meter), who cares about total power output. It’s not like when you win a race, they ask you your power.

    Ride what you like and enjoy the ride.

  12. Great job by Keith and yourself for highlighting this issue. While it has been a while since I’ve done any FEA, I understand the principles that Keith went through in his video. While lots of effort could be spent by Shimano and 3rd party companies redesigning PMs for these cranksets, it seems to me that this effort would be better spent on simpler pedal based PM designs as a simpler platform for strain guages/PMs. i.e. get to closer to the “source of the force”, and thereby reduce relative system complexity. In the meantime, what Keith and yourself have done for PM consumers in highlighting the potential misrepresentation of PM accuracies by companies using Shimano crank-based PMs is very valuable. Thanks again for your time and persistance.

  13. Just out of curiosity – Have you tested these power meters using more or less the same protocol outside? Obviously without ERG… 🙂
    I hope I’m not mistaken, but from what I understand, all of the data you collected were done on the trainer. Could this be the reason ? (i.e., the somewhat stationery position of the bike).

    1. The tests here were in ERG, yes. I have data from outside.. but not enough to collate and make any conclusions. That’s all this x2 in regard to workload. Which should be done at some stage. ERG (and indoor testing) is almost a perfect environment to test these power meters, and there are a LOT of other power meters that pass the indoor test without a problem. So it comes back to the power meter itself, not the testing protocol.

  14. Thank you and Keith very much for taking the time to test and test and test, your feedback to and connections with the manufacturers and writing (and video) it all up in such a clear way. Very much appreciated!

    Fortunately I haven’t noticed big differences in my power readings. (minus som major error in the middle)

    Listening to Keith, even 5-arm spiders are not really reliable for crank based L/R powermeters.
    So better move to pedal based powermeters?

  15. The greatest problem in this whole thing is the undeniable evidence that many power meter manufacturers have been playing with consumers. They unashamedly turned engineering and science into a marketing venture and truth was lost altogether. We manufacture the InfoCrank® to overcome all the issues in past and present power devices and have been saying these things for over four years, but other than those who need real numbers in order to win gold medals, very few wanted to listen and many people denigrated us for building what they said was an overpriced product. Thanks, GP Lama and Keith for starting this discussion. It needs to be said. The people who try to justify products that do not do as they say need to be silenced by those who demand that accuracy be proven. We totally agree that this is a large problem and it goes beyond Shimano cranks.

  16. Any engineer who understands measurement will tell you that accurate measurement relies on clean data from the sensor. There’s only one place on a bike where you can get reasonably clean data on torque and that is the crank arm. Anything else is marketing. There’s way too much noise from complex strain patterns in pedals, spiders, hubs etc. to hope to get an accurate result in real-world conditions, which is why so many power meters have incredibly complex algorithms to try to achieve a “believable” answer. However, it is not enough to stick a strain gauge on the crank arm, because the crank is twisted as well as bent by the forces on the pedal. The result is that the power meter has to be designed from scratch for accuracy with very careful placement inside the crank arm. To my knowledge only InfoCrank have done this, which is why their cranks are so popular at the highest levels where accuracy really counts.

  17. Shane, I’m wondering how this translates to outdoor riding? I’ve got a dual pioneer unit on a 9100 crankset and haven’t seen anything quite as drastic as a ten watt drop compared to my vector 3 (I use my indoor trainer for erg power numbers so I’ve never tested the crank indoors). From your recent podcast it sounded like outdoor rides were less affected than your erg testing. I don’t want to make any excuses for these companies, but even going up long climbs my L/R balance is typically within 1-2% in either direction. Is it safe to assume that there are issues with accurate power calculations, they are simply less drastic when riding outdoors due to the constant variation in cadence and torque?
    Thanks for the great work mate!

    1. Outside appears to be less of an issue, however without a proper testing protocol I haven’t done any number crunching on this. I could spend a few weeks on it… but the outcome isn’t going to change what I’m seeing here indoors.

  18. Shane, All of the analysis was done in ANT+ mode I presume? Were any of the Pioneer tests performed in their proprietary pedaling mode? Reason I ask is after watching Keith’s video, I realize he’s talking about negative forces in combination with coupling. And since my Pioneer 9100 tracks perfectly with my tacx Neo, it made me wonder. Also since Pioneer is the only company that I know of that actually measures more data than anyone else.

    1. I did a number of tests in Pedal Monitor mode with their CA600 head unit recording the data. Same issue. I’d be interested to see your results from same test protocol I’ve used here as you have a Neo to compare to.

  19. Another respondent mentioned pedal based PM’s. Until the industry has a viable solution, should the consumer go with the pedal PM’s and if so single or dual side?

      1. Hi Shane: I love your content and details. Based upon this article and your review of the Assioma’s I’m thinking of getting a set. Given the Assioma’s have been out for a couple years now, any rumors of them releasing an updated version? Seems the life cycle of tech nowadays keeps getting shorter and shorter. Also, I’m a cycling enthusiast (~ 125 mi/wk) doing mostly group/solo riding. I don’t race. I feel as though dual sided is more than I need because I don’t race so wouldn’t likely need to know if my L/R sides are out of balance. Thoughts/recommendations?

      2. I haven’t heard anything about updated Assiomas. They’re still releasing firmware updates (one is pending) that improve features of these units.

  20. @GPLama I’ll be interested on your take of the new Rotor INspider PM using the 110 x 4 Shimano bolt pattern. Will this have the same issues due to the asymmetric nature?

      1. I’ve finally got my INspider! After some informal testing, it looks to read about 4% lower than my calibrated Hammer trainer which was about 2% lower than my SRM.

  21. This is excellent. I know it’s limited to shimano cranks but I get varied readings from my S-works Fact crank too (dual sided 4iiii). I wonder if it’s the same issue. At this point I just wanna stick to left only readings and not care about accuracy but just consistency :/

  22. Hi great work at all GPLama!

    I didn’t make so complete tests but as owner of a stage gen3 LR ultegra 8000 powermeter i came to the same conclusions as you.

    I compared this powermeter with some indoor trainer workouts on zwift (tacx Genius smart with dedicated Wheel equipped with indoor trainer tire inflated at 8 bar and trainer calibration done in a “hot state ” to avoid temperature effects).
    I did some power periods training around 200W and 320W NOT in ERG mode. I used a garmin edge 1000 to record the powermeter data on 1 second basis.
    Yes another point is that on my side, everything is updated to the last firmware…

    Roughtly between the trainer and the stage powermeter there is 10% to 12% (for 320W power intervals) difference.
    And i mean the stage powermeter Under evaluates the power!

    I looked at the balance and for my case, the left side gives the lowest value, not the right side.
    I also noticed that during an indoor session the balance is more 46% left 54% right as for outdoor rides it is usually 49% left 51% right.

    the Genius trainer is given for 5% error and in terms of feeling i am pretty confident on that. if I train considering the trainer power value, I feel I train right regarding my power zones.
    I feel the same difficulty and than i had during my annual medical checkup test I did with direct VO2 measurement.

    It is impossible to train with the powermeter on the basis of my medical checkup test.

    The question is, can we expect some improvements on this point from StageCycling in future firmware updates?
    I already had a ticket at the support for that with the *.fit files joined, but I got a fuzzy answer…
    Or should I directly look for another device, quarq dfour 91 or likewise?

    Best Regards

    1. I don’t believe the issues can be resolved fully within firmware. No word from any vendor mentioned in this report since publishing.

  23. I would be very interested to see the data from the exactly same test, but with different riders. I have the feeling manufacturers are looking at the data from various test riders then applying corrections to fit the data to the output measured by another more reliable device. So, when this is done, the result will better for anyone with the same torque output as the test riders. However, even in my case with my R9100 4iiii Dual, I originally thought what I was seeing was that as power increased, the L/R balance shifted more to the right. But when I compare trainer to non-trainer data I can see the on average the balance shift is more closely related to that, as in 53%/47% (L/R) for trainer, 47%/53% (L/R) for outside. Honestly, my take on this is what a huge waste of money spending $500 US to have 4iiii install the right senor to decrease accuracy.

  24. It appears my Stages LR Shimano meter has the same problem. I’ve shown a slight imbalance 52/48 with Vector 2 pedals, but my Stages has started showing in the neighborhood of 65/35. Question: For FTP testing, my options are (1) using both sides of the Stages LR, (2) shutting off the R and use only the Stages L, and (3) mounting up my old Garmin Vector 2 Shimano pedals. Which option would you think would give me the most accurate results?

    1. When installed and calibrated correctly, the Vector will likely give more accurate results for the test protocol as documented in this report.

  25. thanks for this big research job!
    i wasn’t expecting that, since everybody is telling me that the worst crankset-powermeter is better that the best pedal-based one.
    so i assume this isn’t true. given the same crankset (in my case ultegra), it would be more accurate an assioma or (my potential choice) the srm-look exakt, than the “giant system” i’ve been proposed. right?
    (my whole dilemma is bounded by budget issues, of course).

    1. The Assioma DUO have been far far FAR better than any dual Shimano based power meter crank I’ve ridden. This includes the three additional ones I’ve tested since this report.

  26. I’m very new to this and was hoping to clarify if it would be in my best interest to sell my right sides.
    I have:
    Stages L/R Ultegra – road bike
    Stages L/R Ultegra – gravel bike
    Stages L XT – on two mountain bikes
    Indoor trainer – Elite Direto direct mount power trainer

    Your review states:
    – Variance higher at 350W & 450W ERG.
    – Differences not as pronounced in random terrain SIM mode or riding outside.
    – Harder steady-state efforts indoors (SIM) and outdoors does reproduce this issue.

    I’ve never been on a steady training plan and honestly after googling I still don’t understand what ERG and SIM mean in layman terms. Pardon my ignorance on the topic but I’m trying to weigh out my options if I want to even keep my hardware.

    Do your findings more or less mean the following?
    -L/R are accurate in normal outdoor rides
    -L/R are accurate in indoor rides where the wattage is constantly changing
    -L/R is innacurate indoor when riding a constant hard wattage
    -This is due to using more up-stroke in ERG mode?
    -If I use the power readings from the trainer for ERG mode and the Stages L/R outside, they should both be farely accurate?
    -The L/R balance would still be accurate outdoors (outside of ERG mode?)

    Otherwise, if the Stages L/R is say 5%+ off in all scenarios, I’d just as soon sell the right side and assume that doubling the left side would be just as useful (altho not that great regardless).
    If it’s really that bad I’m also going to plan on selling all my crank meters and buy the SPD Mountain based power meters once they release this year. I’d hate having to switch one set of pedals between all my bikes, but I don’t see the point in keeping thousands of dollars in inaccurate hardware.

    1. There’s not a lot more I can conclude beyond what’s published here. If the unit was off by 5% in all scenarios, companies could simply bump the value and be done. It’s a LOT more complex than that. You’ll get a different (or no) answer on this from these power meter companies as this is a problem they can’t (and haven’t) solved with the current Shimano cranks they’re using. Personally and professionally I’ve stopped using Shimano based L/R cranks for any baseline power comparison. Period. There are other options on the market that are more accurate and reliable.

  27. Does this problem occur with the latest 105 R7000 crankset or is it just limited to Ultegra and Dura Ace?

      1. Thanks Shane, looks like I will be going for the Power2Max option with the Rotor cranks then.

  28. Nice work!

    Do you think a dual-sided power meter variance is consistent from day to day? If so, we can account for it so all is not lost (even if the variance is non-linear).

    A little background:

    Three years ago I started training with power using a 2017 KICKR, without a power meter on my bike.

    Then I bought a bike with eTap and a Quarq D-Zero power meter. The power numbers from KICKR and Quarq were very close (within a couple of watts). Happy days!

    This year I replaced the KICKR with a Tacx Neo and found the Quarq was 10% higher (consistently and across all power outputs). If I rode ERG mode in Sufferfest at 270W on Neo, my Quarq/Garmin 520+ reported 300W, a sprint at 980W on Neo shows up as 1100W on the Garmin.

    My big question was “how to get the Neo and Quarq to match”? I mean which one is “correct”? Just because KICKR and Quarq matched previously doesn’t prove that Neo was incorrect, e.g., two wrongs don’t make a right.

    A few calls to Tacx and Quarq didn’t do much to clear up the situation. I interpreted their feedback to be “it would be rare to have a rear-wheel based power meter (Neo) closely match a crank-based power meter (Quarq).” The 10% variance was totally within “spec”, according to both of them.

    I decided to use a Neo-based set of numbers for indoor training and a Quarq-based set of numbers for outdoor training. Or to think about it a little differently: I’m just a little weaker indoors! Not ideal for Zwift racing, for sure….

    For this season I bought a bike with Dura-Ace 9100 cranks and a 4iiii dual-sided power meter. Provided the variance from the 4iiii are consistent from day to day, I’ll just continue to use a different set of numbers for indoor and outdoor training.

    Thanks for any insight!

    1. They’re consistent with reading incorrectly. It depends on the pedal stroke too.. so there’s no quick fix or easy way to account for the losses. This crank design appears to be a lost cause for everyone who’s selling them as accurate meters (regarding my testing protocol). Power meter companies seem to get frustrated quickly with these power accuracy / comparison queries. It’s REALLY hard to know what’s accurate, but not impossible. It’s the easy-out for them to dismiss differences as ‘drivetrain loss’ or ‘the other power source is wrong’ answers. The cycling tech industry is largely unregulated and self governed.

      1. Thanks for the insight!

        I only stumbled upon your data after reading a comment in a recent Cycling Tips article about Shimano buying Pioneer (CT -> DCRainmaker -> GPLama). I was blissfully ignorant last week =)

        I wonder how all the pros riding Dura-Ace are dealing with this situation – do you have any visibility into that?

        I’ll keep you posted on what I find out from a longitudinal standpoint.

      2. The pros are using these power meters as that’s what they’re paid / contracted to use. It’s not by choice. It’s likely Shimano will address this mid-year with the 2021 release/refresh of the Dura-Ace line – at which point this problem is solved. Assuming they can make an accurate power meter.

        RE: How they deal with the issue. Hmm… I’ve heard a few things. Nothing I’ll repeat here. 🙂

  29. So, my dilemma is that I cannot use the non-drive side, crank mounted PM due to chain-stay clearance limitations. It was suggested to me that I get a right-side PM to avoid clearance issues, and I came across this fantastic article…but then I got to thinking:

    Assume an 8% underestimation in power on the right-side and assume my right leg is 8% stronger than my left, wouldn’t I get a more representative read of my real power, all else remaining equal?

    It’s a hack, I know, but just throwing it out there for commentary.

    1. If your right is actually stronger and it’s being underestimated, my logical mind would think that you are going to get wrong value anyways.

  30. There are a lot of open items still listed. For example, data being crunched and a response pending from Pioneer, more data to Stages for analysis, etc.

    Has this died? Is there new information? Could we get an update?

    1. Pioneer have announced they’re getting out of the power meter game. Zero feedback from any of the other vendors. I’ve tested a number of other cranks from smaller vendors since. Same issue.

  31. Hi Shane,

    Great work. What are your thoughts on the XTR crank – would it suffer the same issues? The design is similar in that it’s 4 bolt asymmetrical, hollow aluminium etc but the shape is quite different.

    Many thanks,


      1. It wasn’t until I actually started riding my PowerTap wheel at the same time as the R9100 4iiii Dual with separate head units that I saw where most of my problem. After comparing about 30 rides both indoors and outdoors and trying to correct the issue mid ride, I saw where most of the issues were coming from.

        The offset on the Right side does not change at the same rate due to temperature variation as the left side. If fact it changes at an unacceptable rate.

        Consistently, if the temperature from the time the offset is complete increases, it makes the right side power and thus right balance decrease.

        Consistently, if the temperature from the time the offset is completed decreases, it makes the right side power and thus right balance increase.

        I came to these conclusions, because I stated to watch the Temperature, AVERAGE BALANCE, AVERAGE POWER and 30 second power on the 2 head units, one paired to a 4iiii dual one paired to a PowerTap Wheel on rides.

        I would always do an zero offset (calibration) after the bike was outside for about 5 minutes.

        Inside, the temperature was always increasing from the start of my rides in the order of about 5C, and the right balance would always decrease throughout the ride.

        Outside, the temperature usually decreases from the start of my rides by anywhere from 2 to 10 C, the right balance would always increase.

        Once I started seeing the average balance shift on my rides, I simply re-did a zero offset (calibrate) on the crank. And when doing this the balance difference from Left to Right and the power difference between my PT and my 4iiii dual is much less. And usually if the average balance had shifted, it starts shifting back closer to 50/50 after doing a calibrate.

        As long as I am doing an zero offset for every 2C change in temperature, the balance is usually:

        49% L / 51% R for Outdoor
        51% L / 49 R for Indoor

        While there is still a discrepancy due to indoor or outdoor riding, it is an acceptable level.

        However, given that every time I ride there is a 2 to 8 C temperate change, I find it very annoying that in order to have the power be accurate, I need to re-zero 4iii dual multiple times on a ride.

        Every Power Meter designed MUST be able to reliably and AUTOMATICALLY keep the offset on the device zeroed through any level of temperature change. Every crank based Power Meter I have ever owned has had problems offset shifting due to temperature change and then in turn making the power inaccurate. I find this extremely irritating that this is still a problem, given these devices have been out for 25 years and still cost too much money.

        So, if you are having problems with the large discrepancy in the balance. I suggest watching the AVERAGE BALANCE on the head unit and doing a calibrate repeatedly on your rides. The first calibrate needs to after the bike has temperature has stabilized to the workout environment, so after 5 to 10 minutes, after that do a calibrate for every 2C in temperature change.

      2. The InfoCrank has automatic temperature compensation by built-in hardware design. It literally never needs offsetting again (after the initial one). It is one reason why so many national federations purchase them for their national teams…

  32. Hi. Great research. Do you think I’d see similar issues with a Shimano XTR9100 RIGHT side? The R & L arms appear to be same and chainring is a direct mount. Thanks.

  33. I’m sorry but there seems to be a huge problem with the control in your testing.

    You can’t just put a trainer in ergo mode at 250w and say that means that the perfect reading for a single sided meter would be 125w – the ergo mode will have a smoothing period, and unless this was implausibly tiny there will be variation in the amount of power your left and right leg are putting out.

    In short, the ergo mode doesn’t care if one leg is doing 140w and the other 110w.

    So that leaves us with the comparison between the pedal’s power and the crank power – and most of the time the pedal power meter is reading below this ideal 125w anyway – meaning that, if we assume the pedal reading is perfect, the cranks are at the very least less inaccurate than they are being portrayed.

    It could also mean that the pedals are inaccurate and the cranks are spot on – we just don’t know (and can’t, without a completely one legged testing protocol – so pedalling in ergo mode with one leg, or with a hub power meter to confirm the power reading.

    But really, who actually cares if the balance/single sided power reading is off so long as the total power reading is within spec? You’ve not shown any numbers that have inaccurate total power readings, but you’ve made reference to them – if you have the numbers, lets see them!

    Taking the example of the Shimano R9100P, DC Rainmaker’s testing didn’t find any issues, the 5k runner has performed testing with the latest firmware and not shown any issues…. so I’m failing to see how we can leap to saying that they are wrong, and that the Shimano PM is inaccurate based on an obviously flawed testing protocol.

    I appreciate where the article is coming from – superficially, it would be understandable if there was an issue reading power from the asymmetric cranks – but the numbers you’ve given don’t prove it, and with others having tested numerous units on a more conventional total power protocol (against two other power meters) and not having seen any glaring issues, to introduce this as a big problem just feels like FUD.

    1. “Shimano R9100P, DC Rainmaker’s testing didn’t find any issues”

      I found significant issues with the Shimano R9100p. Just as I’ve seen with the latest generation 4iiii crankset based on the same Shimano R8000/9100 series models. I didn’t see issues on my first Stages LR crankset I tested, but I have seen occasional issues on a later unit I picked up a year or so ago (an updated the review to reflect that). That’s part of the variability issue here.

      But the R9100P is pretty much universally bad.

    2. I have no problem with my testing being shot down, proven wrong, disputed. That’s why I asked every manufacturer, including Shimano, to review this and respond prior to publishing last year. It was also why I asked Keith Wakeham to review and respond. Please watch his video. It goes a long way to discussing the technical detail.

      Let’s set aside my testing protocol and Keith’s detained explanation of the known issue.

      The questions remain. Where are the missing watts? What is causing that issue? And why are these missing watts so consistent across this power meter design?

      As Ray has replied here, you’ve stated there were no issues with the R9100P, which wasn’t the case. You’ve stated I don’t show total power, it’s in one of the graphs posted. And comparing right pedal/right crank power channels removes the ERG from the picture (and still shows the issue).

      The manufacturers admit to these issues in a marketing/PR friendly way. An engineer who was involved in the original design of these cranks has acknowledged the issues and presented a 30min video on the subject.

      Again, I have no problem with all this data being thrown away. You need to provide a much better case than this. When you do, I’m on it. I’ll be the first person to test, re-test, and re-publish the results. I want to see this issue resolved.

      1. I do appreciate you both responding, first off.

        Ray, perhaps I’m misrepresenting what you said, but in your review you can’t seem to find anything wrong with the total power measurements – there are quirks when you look at the LR balance/single legged readings, but the overall impression I got from your review was that it’s overpriced, but otherwise a perfectly workable option?

        And it seems there is at least some scope for it’s performance to have improved with the latest firmware in any case.

        GPLama, I did watch Keith’s video – certainly, there are challenges caused by the asymmetries – I can well believe that these power meters are less than perfect, as a solution.

        But the testing I’ve seen and scrutinised seems within the spec of 2% on total power readings – why should Shimano or whoever care if they’ve hit their target accuracy under normal readings?

        And if the total power readings are 8% off (or even 4% off) then I would totally agree, yes, we have a problem – but you’ve not listed those numbers? I can see the graph but it’s hard to make out without zooming right in.

        And you haven’t responded to the obvious flaw in taking the ergo power and dividing by two to give a basis for comparison – do you not see how this is a poor baseline for that table? The fact that the manufacturers (or anyone else) haven’t pointed this out doesn’t stop it being a flaw.

  34. You’re reading into the ERG too much. It was a basis for power control. Let’s discount the ERG numbers and look at RIGHT (pedal) vs RIGHT (crank). There’s a problem there.

    I’m not leaving out total power for any reason other than to get to the point about the right side data being the issue. I’ve reviewed data from a number of LEFT only Shimano cranks and they’re pretty good.

    I could include total power, as I have in all my other more detailed product reviews/data comparisons over on YouTube… but that’s more of my time to show the same thing. Lower power numbers using my testing protocol with these type of meters.

    I can’t use these meters as a trusted/reliable source to compare other power meters (and smart trainers) to.

    I have no agenda here. I don’t sell these things. I don’t work for any power meter companies. I simply want answers too. This report and my conclusions are the best I can come up with. As my previous reply, I’m happy for everything here to to be proven flawed. But where are my missing watts? It’s not an imbalance issue you’re trying to point out.

    I’ll leave this here. If there’s any further testing to be done using another protocol or other equipment, I’ll loop back to it.

    1. No tech expertise, but ridden maybe 20 powermeters over 15 years. Searched this as I have been training on a Quarq with values I would expect as a 300km a week, 320W FTP rider. I have recently gone back onto my ‘best’ bike with the Shimano unit, completed some very fast rides at the power I was targeting (2hrs @35kph at 230W avg- I am 76kg!) and been totally in a box afterwards. Knew it wasn’t right. Sadly I have two of these, and been blowing up at midpoint on my TT bike also.

      1. To anyone experiencing large discrepancies, I would highly recommend to repeatedly re-zero (calibrate) your power meter repeatedly throughout your ride. As in once every 15 to 30 minutes. Just to see if that makes a difference.

        I did extensive testing on the my 4iiii 9100 dual crank and was not able to see the problem at the magnitude as presented in this article. However, I saw an even larger problem with power numbers due offset shifting in an unbalanced manner due to temperature change. See my prior post on this thread for more info.

  35. I’m so disappointed for just had read this article after spending USD1.000 in a Stages LR Dura Ace 9100 Power Meter.

    Just tried it yesterday and I got completely shocked for the numbers obtained, instantly thought that something was wrong and now I came across with this article which confirms that the product I have bought is completely useless. What a shame

  36. Hi. I just purchased a new bike with a Shimano GRX FC-RX810 Crankset. I will adding a 4iiii power meter to the crank. Watcha think? L/R or just L? Thanks for help.

  37. Hey there
    My canyon came with the Dura ace PM preinstalled.
    There’s been a FW update not long ago.
    Do you happen to have any update on the issues presented?

  38. Firmware and software cannot be upgraded to fix problems due to installing power devices onto cranks not designed to measure power. You can have a purpose built crank and a very nice one, but you can’t just stick something onto it and get a proper power meter. What you can get is something that purports to be a power meter. Eventually, people start to realise it, but the horse has bolted. The manufacturers have got away with it and in reality you have no idea what the instantaneous torque or power is anytime. Can’t be fixed! Alternatively, you buy a purpose built power meter, preferably in the crank that was built to direct the forces and measure them. Then you have different issues, but at least they were designed in the first place to do the job.

  39. this is wonderfully helpful information, but what is simplest answer for a Trek Checkpoint Owner (Ultegra) needing a power meter. Left side not an option due to clearance but I’m now concerned the right side only will be wildly inaccurate.

  40. Hi. Great thorough report. Do you know if this apply to Shimano Dura Ace 9000? Cause I was going to buy 4iiii dual side…
    Thank you very much for your help.

    1. To complete my question: …becaus in the video it about the asymmetrical shape of the right arm of the DA 9100, which is not the case on the 9000. Thanks again.

  41. Hi, great article and details!
    Do you have any plans to test the GRX cranksets to see if they are susceptible to the same issue?
    I’m trying to decide between a L or R powermeter for a gravel build and the extra clearance by going with a R side-only power meter would be welcomed, just want to avoid the issue described.

      1. Thanks for the reply! Now if only the supply side gets sorted and you can get your hands on a chainset 🙂

  42. Thanks for the article, I just wanted to take the Stages Power LR Shimano Dura-Ace R9100 and now changed my mind. I understood correctly that you need to take Favero Assioma or QUARQ DZERO? =)

  43. so they sell not calibrated power meters ??
    they should attach the unit to crank, then stress crank arm to few predefines forces and program/calibrate power meter unit with acquired data.

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