Shimano Ultegra Fc-6800 Power Meter Left Crank Review
This report presents clear evidence, based on robust information, that power readings derived from dual sided cycling power meters using Shimano cranks, does non provide consistent levels of accuracy as specified past power meter manufacturers.
The Shimano alloy crankset is a popular base of operations unit for a number of companies to utilise for their power meter products. Not originally designed every bit a ability meter, electronics engineers successfully mounted strain gauges on the left side creepo only (where power was doubled) to give cyclists a more cost constructive way of measuring their power output.
Stages Cycling was the outset 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 nearly every company started offer 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'southward not as inexpensive as a left-only offering) dual sided power meter, independently measuring left and right ability, and reporting metrics such equally pedal residual and true total ability output.
From an engineering perspective the right side Shimano crank power meter has been a challenge. The pattern and shape of the right crank is very dissimilar from the left, and with Shimano irresolute the shape from the FC6800/FC7900 with the R8000 and R9100 right side cranks for a wider four arm arm/spider interface, things became fifty-fifty more challenging for them to obtain accurate power (torque) measurements from. At that place has been mention of a strain approximate redesign required specifically for the R8000 & R9100 right side cranks.
Over the past year I've ridden and compared ability readings from 11 (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 whatever Shimano R8000 or R9100 Correct side cranks is at an acceptable level for consumers to confidently rely on at this signal in fourth dimension.
I have been in directly advice with a number of the companies mentioned in this report over the terminal 12 months.
None of these companies have questioned my testing protocol, or results for what would be considered successful tests of left-simply power meters and their non Shimano dual sided ability meters.
Each visitor has been provided this report and all data collected on thier power meters in advance for response.
My goal here is to identify problems consumers may encounter themselves with these products. I promise these findings will lead to more authentic power meters on the market.
Background
Strain gauges are a solved trouble. The gauges used today are reliable and dependable. Other power meter features are of a high standard: Battery life. ANT+ & Bluetooth Smart data manual. Active Temperature Bounty (to an extent). If this wasn't the instance the ability meter manufacture would be in trouble.
Digital cadence sensors are likewise typically accurate plenty to obtain quality power output from. (Accurate cadence is required for accurate ability from these power meters). Some power meters yet rely on magnets for ameliorate cadency readings (which are more responsive in my experience). Accurate cadency readings are a part of this bigger picture show discussion, just they're not the main show in this report.
Why are ability meters and then hard to become correct?
Wheel power meters are finer a moving weight scale. Continuing on a bath weight scale requires you to be stationary for accurate results. Power meters require the same accurateness moving at high speed (rotation, vibrations, etc), while measuring multiple strength vectors, in almost all environmental weather condition 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 utilise the same mail-product strain gauge placement blueprint every bit third parties for their DuraAce R9100P Power Meter. Yet when Shimano themselves can't produce a quality manufacture leading power meter from their own cranks from solar day i – there'due south a trouble. A big problem.
References:
– DCRainmaker DA9100P Review: Issues with left/right accuracy.
– Wheel Radar DA9100P Review (Ben Delaney): Bug with left/correct accuracy.
– GPLama DA9100P Review : Issues with left/right accuracy.
Discussions with a ability meter designer/engineer Keith Wakeham on the topic of using Shimano cranksets equally power meters has confirmed there are difficulties with pattern asymmetry, chainring positional affinity, and the coupling effect when using strain gauges on the Right side creepo arm of a Shimano creepo. This is a known problem that isn't limited to just the drive side, all the same it'southward where the issues ascend when using a DUAL sided Shimano based ability meter.
Within Shimano HOLLOWTECH Cranks
Photo Source: https://world wide web.mobile01.com/topicdetail.php?f=316&t=4849613
Photo Source: https://world wide web.mobile01.com/topicdetail.php?f=316&t=4849613
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. Information technology'due south by all ways not perfect, nevertheless it has successfully identified issues that have been best-selling (and in some cases resolved) by power meter and smart trainer manufacturers.
This protocol uses a combination of SIM (Simulation) and ERG fashion. ERG manner forces you to pedal at the gear up 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 aforementioned vendor for all meters if possible).
– 1 2d 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-showtime performed on all units (every bit applicable) at 0 minutes.
– 10 minute ride (SIM mode / Human warm-up / a few brusque hard efforts).
– Dismount wheel. Zero-offset performed on all units / Spindown on trainer (if applicable).
– 10 minute steady-state ERG @200W ~88-95rpm. Both hands on confined. Natural/polish pedalling.
– 10 infinitesimal steady-state ERG @250W ~88-95rpm. As higher up. Balanced, smoothen, natural pedalling.
– Maximal sprint of 5-8sec. Out of saddle. (SIM or Level mode).
– four minutes like shooting fish in a barrel 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 ~sixty seconds in SIM to collect more than 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-merely Shimano based power meter cranks typically report ability within their specified accuracy specification (+/-%). I take 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 accept had left-only cranks from manufacturers non listed in this report that take zero-offset stabilisation issues and power fluctuations. And so they're not immune to issues either.
The caveat with LEFT just is with the doubling of power from ane 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 written report focuses on the Right side crank arm.
References:
Stages Power Meter (Single/Gen Three) – Install, Ride, Data Review
Magene RIDGE Shimano Ultegra R8000 Power Meter: Details // Install // Data Review
XCadey X-Power Budget Ability Meter: Unboxing, Install, Review
Shimano Based Power Meter Cranks: Correct / DUAL SIDED
Here'southward where things get catchy.
Shimano Cranks Tested (11):
– Stages LR (x2)
DuraAce R9100 (Gen iii) 1st Unit
DuraAce R9100 (Gen three) second Unit
– Pioneer (x3)
DuraAce R9100 (SGY-PM910H Emmet+ only model)
DuraAce R9100 (SGY-PM930H Emmet+/BLE model) 1st Unit of measurement
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 (*Guess placement different to the others)
– XCadey 2XPower
Ultegra R8000
Method:
Lama Lab Test equally documented above and here: GPLama How To: Comparing Power Meters // Power Accuracy Testing // DCR Analyzer Tool: https://www.youtube.com/picket?v=JhheDLXRM7I
The Results:
Steady-Land 250W ERG
Power Meter: Crankset used
ERG: 50% of 250W ERG Mode (125W)
Other: Right side power channel of non Shimano Creepo (Assioma/P1/Vector3)
Right: Shimano RIGHT side reading
| Ability Meter | ERG | Other | Unequal % | RIGHT | Unequal % |
| Stages RIGHT DuraAce R9100 (Gen 3) 1st | 125 | 124.14 | -0.69 | 116.74 | -6.61 |
| Stages RIGHT DuraAce R9100 (Gen three) 2nd | 125 | 121.04 | -3.17 | 116.16 | -vii.07 |
| Pioneer Correct DuraAce R9100 (SGY-PM910H) | 125 | 123.09 | -1.53 | 112.half dozen | -9.92 |
| Pioneer Correct DuraAce R9100 (SGY-PM930H) 1st | 125 | 127.87 | 2.30 | 114.76 | -8.19 |
| Pioneer Correct DuraAce R9100 (SGY-PM930H) 2nd | 125 | 122.79 | -1.77 | 116.91 | -half dozen.47 |
| 4iiii DuraAce Correct R9100 (PRECISION PRO (DocSLane 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 | -i.31 | 113.95 | -8.84 |
| WatTeam R8000 G3 Right | 125 | 124.06 | -0.75 | 117.71 | -v.83 |
| Shimano DuraAce RIGHT R9100-P | 125 | 125.67 | 0.54 | 115.12 | -7.90 |
| Behemothic Ultegra Correct 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% | 115.19Due west | –7.85% |
– Variance higher at 350W & 450W ERG.
– Differences not as pronounced in random terrain SIM style or riding outside.
– Harder steady-state efforts indoors (SIM) and outdoors does reproduce this issue.
Isn't this simply drivetrain loss?
No. The discrepancy in power readings is betwixt the pedal ability meter and crank ability meter which are directly connected. The power differences reported are more credible on the RIGHT side. The controlling smart trainer in ERG besides provides a tertiary power comparing source.
What did I compare against?
Multiple sources:
– Favero Assioma DUO (Dual sided pedal power meter. ±i% Accuracy)
– PowerTap P1 & P2 (Dual sided pedal power meter ± 1.5%)
– Garmin Vector 3 (Dual sided pedal ability meter ±i% Accuracy)
– Tacx Neo / Neo 2 (Straight Drive Smart Trainers ±1% Accuracy)
– Wahoo Kickr / Kickr Core (Straight Bulldoze Smart Trainers ±ii% Accuracy)
Basic Formula:
Dual Sided Power Meter Fifty + R = Smart Trainer Power ≠ Shimano Creepo Power Meter Total Power.
eg. AssiomaDUO Power = Tacx Neo Power ≠ Shimano Creepo Power.
More specifically indoors and out: Power Meter R ≠ Shimano Right Crank Power.
Note: This doesn't factor in any specific mechanical losses incurred betwixt the pedal and crank, and drivetrain losses at the smart trainer power measurement signal (effectively the rear hub). However, measured losses are never greater than a few watts (<ii%) of TOTAL ability using a clean drivetrain when cross-chaining using 52/28. Reported power from the Right cranks is upwardly to 10% different, on one side solitary.
I can not aspect 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 price) that it has taken me to reach my current conclusions.
The contained testing of Shimano R9100 LR cranks at the University of Colorado Bedrock 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 infinitesimal intervals at lower cadence ranges than I would expect a trained cyclist to ride (only up to 85rpm). Their summary effect of 1.58% accuracy was an average beyond all data sets with the 3 Shimano R9100 cranks tested.
There was datapoint at ~250W (calculated) reporting equally ~240W. Indicating there is outlying data points. 240W @250W calculated is -three.seventy% equating to -9.7W. What wasn't reported was the Left/Correct power figures on any of these information sets. Yes, I'k being selective here – my point beingness 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 meliorate. With the carbon SRAM XX1 crank achieving 0.84% accurateness on average across four cranks tested. Indicating the gauges and technology used by 4iiii is of a high standard that will produce accurate measurements bold the base creepo it is installed on doesn't suffer from the same problems equally the Shimano RIGHT creepo blueprint.
Performing the Lama Lab Test protocol on the dual sided FSA SL-M 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 (every bit documented above). Specifically longer duration smooth pedalling steady-state ERG efforts in improver to over/under intervals – Tested confronting a long-term known-skilful power sources – Which I consider the AssiomaDUO / Tacx NEO / PowerTap P1 to be.
I have discussed this upshot 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. Information technology requires multiple power measurements on the same cycle at the aforementioned time. Not many cyclists volition install 2 independent Fifty/R power meters on their bicycle. Even less will perform any in-depth analysis of the information. A growing number of cyclists are comparison their bike ability meters to their smart trainers and are reporting ability differences. This issue could very well provide answers to some of those queries.
More oftentimes than not when users ask questions regarding power meter discrepancies in a public forum they are dismissed as 'drivetrain loss' or Fifty/R imbalances. Unfortunately these reasons are echoed past 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 event and why hasn't this been resolved in firmware, or with better strain gauges?
The applied science complexities of this problem is best explained by someone who tin embrace this in the technical particular it deserves. And that person is Keith Wakeham. Keith is ane of the original designers of the 4iiii power meters. Keith is listed on the patent under 'Inventor'. He really knows his stuff. Reference: https://patents.google.com/patent/WO2016030768A2
Keith has a blog over on https://titanlab.co and has put together a post on this very topic: https://titanlab.co/shimano-crank-design-blunder/
If y'all accept a few minutes to keep diving into this issue to the depths y'all never idea possible – Grab yourself a java and watch his video here:
This isn't an wrong slope or miscalibration issue. It'southward 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 TeamX / Mine Reads Fine
Professional teams are sometimes provided non commercially available product. Teams are paid to use equipment (read between the lines hither of what they'll say most said production). Professional teams are also unlikely to perform any power comparing tests to the level required.
"Mine is authentic". Compared to….? What was your testing protocol? How was the information recorded and analysed? The answer here is typically "we'll need more data". Beware. Getting to the reply is a rabbit hole of indeterminate depth.
My Accept Outs….
Shimano based dual sided power meters report lower total power in my tests due to inaccurate measurement of power on the correct side in a number of pedalling scenarios. This is particularly evident in steady-country smooth pedalling efforts across a range of wattages.
At this bespeak I am non confident to use Whatever Shimano based dual sided ability meter crankset as a baseline to compare power readings from other ability meters or smart trainers.
I ain a Shimano based dual sided power meter as referenced above. Does this thing?
Yes:
– If you're using the reported Fifty/R rest values every bit part of your preparation.
– If you're comparing multiple power sources.
– If you take more than than one type of power meter (One that'south Shimano based, and one that is not).
No:
– Yous're not bothered with Fifty/R balance.
– The ability meter is your One source of ability for all training.
– You have more than one of these Shimano crankset ability meters.
– You're non 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 near of the companies named. There is obvious (and admitted) complexities with the Shimano Correct crank design when used equally a power meter.
I understand information technology's non 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 every bit to why these discrepancies have been narrowed downwardly specifically to Shimano Correct cranks – why I'grand 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 Commonwealth of australia:
– Stand behind their ±2% accurateness claims of LEFT and RIGHT Shimano Power Cranks.
– Discrepancies in my provided Right ability data due to bugs in the firmware I used.
– I tested the R9100-P with four.0.7 (March 2018) which is the firmware that their changelog indicates resolves accuracy issues.
– Information technology was recommended I update to 4.1.7 (February 2019) and retest.
– I raised concerns that 4.1.7 alter log lists no updates to power accurateness. Also infers they had an inaccurate ability meter on the market up until February 2019…!?
My Activity Points: Source another R9100-P and retest with iv.ane.7.
4iiii Innovations:
– Acknowledged problems with the Shimano crank asymmetry and non-compatible coupling effects.
– They believe their firmware and scale protocols are robust enough to stand by their accurateness 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 not Shimino L/R crank in the Lama Lab tests, or Dr. Due south.Lane besides recording the aforementioned lower power measurements with the Shimano based Correct crank).
My Action Points: Continue working with 4iiii to provide more information from the Lama Lab and in person across more of their power cranksets (Both Shimano and not Shimano). Ongoing.
Stages Cycling:
– Stages stand backside the accuracy and repeatability of the Stages Power R and Ability L/R meters in the vast bulk of use.
– They mention the loading of the spider and crank is different during the pedal stroke in ERG every bit opposed to SIM or riding exterior – which could be contributing to the discrepancies.
My Activeness Points: Go on working with Stages to provide more data from the Lama Lab and in person across more of their power cranksets (Both Shimano and not Shimano). Ongoing.
Pioneer:
– Data analysis still in progress. TBA.
Giant:
– No response. TBA.
WattTeam:
– No longer in business organisation. RIP.
XCadey:
– Data analysis still in progress. TBA.
Notes/References:
– In comparative power meter testing it is hard to utilize the total ride/activity power equally a measurement of accurateness due to factors such every bit start/stop delays across unlike 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-country efforts.
– The data from the Giant PowerPro has changed with recent firmware updates. From reading loftier on the right, to low, to a random betoken in between, sometimes. I doubtable they are fudging or scaling the left/right to account for these issues. The dataset used here indicating LOW readings on the correct was from fw237 (latest release as of testing).
DCR Analyser: Online tool for reviewing and comparing FIT file data.
Shimano R9100-R Ability Meter tested June 23rd 2018 with Firmware 4.0.7 released 27th March 2018 – "Update to brand output value more accurate"
Technical Written 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 ability-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.
Source: https://gplama.com/2019/06/29/shimano-crankset-power-meters/
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