Those numbers, for the majority of riding conditions (maybe in the "ballpark" for certain longer climbs), are pretty much useless and not accurate for anything regardless of bike.

It's neither accurate on a TT bike nor on a road bike.

If you have an actual powermeter on your bike and are recording the data, Strava reports that data and puts a lightening bolt behind the watts.

If you do not have a powermeter, then it shows an estimated power reading as described HERE and doesn't factor in any environmental differences, ie wind speed and direction, and can be wildly inaccurate.

Thanks I hadn't seen that. I will assume since I have a good TT position, on a well-maintained bike that Strava's estimated average power for a ride is high. I did notice a tailwind going out and a headwind coming back home and Strava's numbers seem quite off in those locations with regards to my HR and perceived exertion.

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Madison photographer Timothy Hughes | Instagram

For entertainment purposes only.

IF they happen to be close, it's like a broken clock.
But yes - I think they're assuming typical roadie, CRR, CdA, etc.

If you want accurate power #'s, you'll hafta upload your PM data to Strava.
I've recently gotten a 4iiii's Viiiiva HR strap, that allows my PT to talk to my iPhone, and then it all uploads to Strava in a jiffy.
(as opposed to having to download from my 310XT, which is very time-consuming).

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float , hammer , and jog

How do you know you have a good position? Just because something looks aero to you doesn't mean it actually is. I assume by your lack of a PM you have gone for aero testing in a velodrome or wind tunnel...

It's neither accurate on a TT bike nor on a road bike.

WHAT?! You mean I don't have a 400W FTP? No wonder I'm so slow...

Yes, the Strava estimated power is ~100w high for me on a flat road on my TT bike. In many cases it will show numbers in the 400+ range on longer segments. I'm incapable of that type of effort.

It is pretty close on climbs of more than 90 seconds or so where the speed is <30kph on either bike.

It is grossly LOW on the dirt on my CX or MTB.

-SD

Thanks. What's interesting to me is that Strava has loads of power meter/map data from user uploads. The courses I train on are very well-trafficked by cyclists of all abilities [many with bonafide PM] and Strava accounts.

So in the same way google maps generates real-time traffic data by numerous commuters using GPS/Google maps simultaneously, I'd also assume Strava has accumulated a very nice database of actual power numbers to coincide with their segments.



Geez. Well, I was guessing something like 4-6% or 1mph difference. Now I just feel terrible about my Saturday shakeout ride numbers. : P

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Madison photographer Timothy Hughes | Instagram

As others have said it's about as accurate as a random number generator.

Iain

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