Losing watts with a pair of bora ones

[blaugrana]

Perform a rolldown test already, or stop posting useless anecdotes. Do several runs with each setup as well.

But with a rolldown test the freehub drag will play a part as well. I don't know how many watts that would be, but it's probably not insignificant, especially if both are on the factory grease, so the fill rate and viscosity can be different.

[mrlobber]

All the arguments about "we've had similar times with my friend" etc are useless for any conclusions unless controlled for a myriad of other variables for BOTH of you, such as accurate tire pressures, weight in that particular day, power meter calibration (including possible temperature drift), even wind direction, as it could easily be that one of you has had somewhat sheltered ride, and many other things.

As a counter example - I ride ~50 km on the same road just about every morning within +/-10 minutes (so pretty similar traffic conditions).
One day, my average speed was ~33.5 kph with my aero disc bike, 1x drivetrain, 60mm wheels with Conti GP5K TL, so, just about as aero & fast rolling setup as you could get. The next morning (wind was from the same direction, just 1m/s stronger; I forgot to check the atmospheric pressure, however, the weather didn't further change for 2 days) I took out my long-in-the-basement-sitting 25x23mm rim brake tubular wheels on a SL6, and rode the distance at 34 kph, with 2 watts of power and 1 bpm of HR difference. So... should I conclude that 25mm wheels are more aero than 60mm wheels?

[ArizonaPie]

All the arguments about "we've had similar times with my friend" etc are useless for any conclusions unless controlled for a myriad of other variables for BOTH of you, such as accurate tire pressures, weight in that particular day, power meter calibration (including possible temperature drift), even wind direction, as it could easily be that one of you has had somewhat sheltered ride, and many other things.

As a counter example - I ride ~50 km on the same road just about every morning within +/-10 minutes (so pretty similar traffic conditions).
One day, my average speed was ~33.5 kph with my aero disc bike, 1x drivetrain, 60mm wheels with Conti GP5K TL, so, just about as aero & fast rolling setup as you could get. The next morning (wind was from the same direction, just 1m/s stronger; I forgot to check the atmospheric pressure, however, the weather didn't further change for 2 days) I took out my long-in-the-basement-sitting 25x23mm rim brake tubular wheels on a SL6, and rode the distance at 34 kph, with 2 watts of power and 1 bpm of HR difference. So... should I conclude that 25mm wheels are more aero than 60mm wheels?

Uh that's very different lol. That's more similar to the tests I do on different days on the same hill, which I agree aren't very easy to compare.

I guess I'll just have to agree with Steve on this one.

[TobinHatesYou]

But with a rolldown test the freehub drag will play a part as well. I don't know how many watts that would be, but it's probably not insignificant, especially if both are on the factory grease, so the fill rate and viscosity can be different.

Actually it's pretty friggin' insignificant vs gravity and your momentum.