Why does Strava crop metrics numbers?

Equipment
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I’ve noticed on a few occasions that Strava crops or reduces the value of some key metrics when the data is uploaded from my Wahoo Bolt.

I’ve had this happen with average speed and power most notably. Past examples being power numbers over set time lengths all being lower and /or average speed being up to 0.2mph different for the ride.

Example in point - today about 60% of way through my ride I lined myself up for a short uphill sprint, with a nice tailwind and selected the perfect gear for optimum cadence, and banged out an maximum effort over around 45 seconds.

I’ve been working slowly on improving my sprint numbers over the last few weeks and this one felt really good. I’m nowhere near my past best but I had a good feeling.

Wahoo showed a peak of 1404w which felt about right. Strava took that data and reduced the peak to 1293.

I could understand some minor differences perhaps due to the way that the Strava algorithm works with data from different sources - but over 100w is a massive % change - which I don’t understand.

Any else experience this? Does anyone have a clear explanation as to why? :man_shrugging:t2:

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This is one reason I never use Strava to look at stuff like that. Seems to do all kinds of weird things with the raw data.

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I see differences in peak metrics across apps. A peak can be very short, perhaps one datapoint. This can be legit or it can be “noise”. Some apps will average over several point which can bring a very short peak down. I think it’s better is to look at an average over 3-5 seconds. This will agree much more closely across apps.

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I see the biggest difference the more I stop or go slowly, maybe autopause. Whereas on TTs where I pedal continuously there’s no difference.

Another area I can see relatively massive difference is on the Max speed, where GC and Strava can be several mph apart.

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