Originally Posted by
jadocs
Here's another factor, he sets his Garmin to pause when he hits a certain speed....not sure if he has it set at 3mph or what, but that severely skews your actual average speed which also throws off power estimate. In summary he's not as fast as Strava thinks he is.
Strava ignores custom auto-pause settings. I have my auto-pause set to 0mph, and Strava will always manage to add around 30 seconds of moving time to a 90 minute ride. I've had Strava tack on as much as four minutes to rides where my total stopped time as recorded by the device was less than 7 minutes. I call it "Strava Math." So that guy isn't helping himself with auto-pause settings. Now running a wheel speed sensor and setting it to a larger circumference, that will artificially inflate average speed.
On topic, I found that Strava's "estimated power" was fairly close to my measured power, after recording 200+ rides-- and only when viewing power for an entire ride, not segments or individual efforts. Most of the routes I rode with and without power were in that 5% area for variance, unless other variables came into play. For most people, Strava will always guesstimate high, because I think low power numbers make people sad. Just like how they always inflate calorie burn numbers. People like those big. Strava always counts zeros when doing power measurement, then gives you a weighted number, which is pretty close to average power when not counting zeros. They just like to throw on an added layer of math.
My current favorite Strava + power meter game is highest possible average speed with lowest measured power. Once Strava Math is done with it, I can go pretty far, pretty fast, for very little power output. Two weeks in a row, ~75 miles @ ~17.5mph from ~155W. Weighted in both cases right around 200W. I guess I'm a very effective coaster. Pedaling time in the 80-85% of activity area both times. I've learned to just take it for what it is. So long as the load/stress scores are consistent, I can use the power meter for what I bought it for in the first place-- not overdoing it.
Stages (in my year of experience, anyway) isn't far from Strava in terms of padding the numbers. I know every meter is a little different, but when I switched from Stages to Power2Max, my FTP immediately dropped 40 watts. Turns out it
doesn't take 250W average to do 19mph for an hour. I do miss those Stages numbers though. Three plus hours at 240W average? Looks good. Now, 70 miles in 3h37 @ an avg. speed of 19.4mph? Like 180W. Somehow less impressive. Maybe I've just learned to be
super aerodynamic.