Different Power Data Between Strava and Powertap/Garmin

HI, I've noticed issues related to power measuring/output/estimations. I am using a Garmin Edge 1000 paired with Cycleops Powertap G3. My last ride, the one from this morning is showing on the Garmin 160w average and 161 NP and Strava shows 130w average with a weighted average of 139w. Also I performed a FTP test on a Cyleops trainer and the value is 208w. When uploaded to Strava it turned down to 165w. Can you please tell me why is that the case? In past there was a problem with elevation correction, but I see it was rectified, so there is no elevation correction from Strava on data from Garmin devices. 

Looking forward to an answer. Paul

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  • Hey Paul,

     

    Like you I have the same trouble with a Wahoo Elemnt and a Garmin 1030 combined with a Shimano dual power meter.

    My power stats get dropped by 15-20% after they are uploaded to Strava.

     

    Today the Garmin / Shimano PM reported a ride I did was 216w Average or NP of 205w - Strava shows 180W

     

    Does my head in ....

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  • Hey Ian. Power meter data should superseed Strava estimates, but alas it doesnt. I'm guessing this is the case because of the many users of the mobile app. An option as to disable these estimates would be in order. Maybe we can get an official answer. Garmin Connect and TrainingPeaks take data with no modifications from the powermeter...

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  • Yes I agree - maybe the ability to have a setting to use "Raw" data so Strava doesnt modify it.

    I cancelled my Premium membership over it as its really no use for recording accurate stats when they run their algorithm over it and change everything.

    Seriously how can Strava estimate Power when I have Actual - aarrgghhhh!

    Now I use Strava as a Facebook - Social side only as no serious user can take these stats as correct.

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  • Sad that this is still an issue on Strava.  Speaking as a Senior Software Engineer, the data is the data.  I've never personally worked on or implemented a system that changes data from the authoritative source.  In this case it's the sensors that generate the data and the cycling computers that collect the data from the sensors.  This is the major reason why I have not signed up for Strava's premium service.  Why would I pay someone to change the data I worked hard to achieve.  Basically, Strava is asserting that the power meter, sensors, and cycling computer that I've paid good money for are all wrong.       

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  • Can not more than agree.

    And this has been going on for a long time. 

     

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  • Hi, I filed a support case for this one

    I actually subscribed to the analysis bundle of summit because wanted to dig deeper into my training since I am starting out.

     

    I asked support to give me a workaround so I can have strata show raw power data (uncorrupted). from a Data perspective, their "smoothing algorithms" should only be used for estimated power and not actual power.

     

    I too, will cancel my premium over this since it appears that Strava corrupts data. Premium membership might be better spent on trainer road or training peaks.

    I wish Strava had a functionality to disable the annoying estimated power when we have the raw real power data.

     

    It just does not make any sense or logic. From a data perspective they should at least show the original data unadulterated then show the "Strava" data.

     

    This is happening with times for my runs as well. Strava just loves corrupting data.

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  • Hello All, 

           I like so many of you experience the same problem with STRAVA, altering my data, from my Garmin Device.  I have experienced the same problem with utilizing two different power meters, Stages and 4iii, both recording to my Garmin Edge 530, (different bikes).  As with your experience, despite the power meter used, when uploaded to STRAVA from my Garmin device, the power readings are corrupted.  The same I have noticed with people using WAHOO.  Specifically (AVG Power), (Normalized Power or Weighted Power), (TSS), (Intensity).  The significant difference in readings renders utilizing STRAVA as a training platform useless.  

         On the other side of this, I have witnessed friends' readings from their BRYTON computers, transfer to STRAVA accurate data.  So this leads me to believe that STRAVA's algorithms change depending upon what the computer is collecting the data, or rather "Computer Manufacturer".  Why would Strava corrupt, change power reading data coming from a device and not another,  and how do they see this "benefiting" an individual. 

         STRAVA, in their defense, stipulate they change the data because of potential inconsistencies on what their knowledge of road/terrain and type of bike you ride..  ie...Horse Shit... 

    "We have seen that in most cases our watts numbers are very close to the numbers provided by a Powertap or SRM. Note that Strava calculated watts are not the watts produced at the crank but the watts produced by the rider-bike system, this will create a slight difference between the power meter data and the Strava watts. Lack of good chain lubrication and low tire pressure can rob you of the watts you see on your Powertap or SRM. Other reasons watts can be inconsistent include strong winds and bad elevation data reported by the Garmin. Our calculations are most accurate when climbing given accurate rider and bike weight."  (https://support.strava.com/hc/en-us/articles/216917107-How-Strava-Calculates-Power)   NOTE: they actually mention "GARMIN"...  

          Simple solution, just as STRAVA has a toggle link for elevation, allowing the individual to "Correct" their elevation, apply the same principle for our "POWER" readings.  Allows the individual to select "RAW" (data coming from a power meter) or Strava's Corrected version.  Better yet, have this option in your profile as a default for your rides.

    R/ Paul

     

     

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