Weight Weenies

Assume a very, very good road bike CdA of 0.25, 80kg system weight, typical bling aero road bike kit (helmet, roadsuit, deep wheels, etc,) fast tires, average quality flat road, calm conditions, sea level air density for 20C/68F. Do not consult a speed/CdA/power calculator.

I guess I:

1. Know my road CdA which is close to that
2. I weigh much less than that (tho weight is inconsequential on a flat course, once rolling)
3. And, in season, I'll TT half a dozen times a month
4. And off-season, I tune my CdA....
5. ...and I frequently look at air density, tarmac conditions, Crr.... pre and post race...

.... I literally sit next to a Dew Point/Humidity/Temp monitor, and I review wind patterns for important days.

...soooo.... I don't think I should play this game but this is a very fun game indeed.

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maxim809 wrote: ↑

Sun Nov 27, 2022 3:47 am

I guess I:

1. Know my road CdA which is close to that
2. I weigh much less than that (tho weight is inconsequential on a flat course, once rolling)
3. And, in season, I'll TT half a dozen times a month
4. And off-season, I tune my CdA....
5. ...and I frequently look at air density, tarmac conditions, Crr.... pre and post race...

.... I literally sit next to a Dew Point/Humidity/Temp monitor, and I review wind patterns for important days.

lol

there's not much more to say, i know

In complete contrast, I guessed Ganna's hour record power, guessed that the road bike drag would outweight the 5kph difference and so added a bit. But now I think that was probably totally wrong and 51kph on a road bike would be easier than 57 on a TT?

385 watts

Well at least my guess was what 31% of all have guessed at so far but I did do a little math to approximate. Thank god for W/kg or I wouldnt have a clue outside of that the cda calculations I paid no attention to much.

When do we find out the correct answer?
What do we win?

Chaunch wrote: ↑

Thu Dec 01, 2022 11:46 pm

When do we find out the correct answer?
What do we win?

Closest would be 500W. Depending on the quality of the road and the tires, it could be very slightly under 500W, but not close to 450W. 0.25m^2 is also quite difficult to achieve on a road bike. An already good aero position on a road bike would be 0.27m^2, which would raise the power requirement into the 530W range.

I answered 350w as I was fully expecting this question to be a trap - I thought it was going to be more like 400-450. I guess it shows that I am not used to holding these wattages..

I went with 450W but realized quickly i underestimated the power output required after submitting. Its definately close to or above 500W for an average sized rider around 75-80kg without any gradient or helping tail/cross wind. Maybe I'm wrong again

I do that easily on my TT bike at 300 watts so I think 350 for the road sounds about right

CustomMetal wrote: ↑

Fri Dec 02, 2022 11:44 am

I do that easily on my TT bike at 300 watts so I think 350 for the road sounds about right

Are you a tiny person or is that downhill with a tailwind?

'Cos you can look at known performances for track riders on pursuit bikes in perfect conditions holding those averages and it ain't 300 watts.

Karvalo wrote: ↑

Fri Dec 02, 2022 7:36 pm

CustomMetal wrote: ↑

Fri Dec 02, 2022 11:44 am

I do that easily on my TT bike at 300 watts so I think 350 for the road sounds about right

Are you a tiny person or is that downhill with a tailwind?

'Cos you can look at known performances for track riders on pursuit bikes in perfect conditions holding those averages and it ain't 300 watts.

Flexible and very narrow/low CDA going on UK 10 mile TT courses, (highly optimised) but then I could have had more favourable weather conditions

Keep in mind I stipulated 0.25m^2 CdA so assumptions about flexibility/size don't really matter. 0.25 is close to as good as it gets on a road bike without resorting to 32cm bars and what-not.

At 300W with a Crr of 0.003, you would need to be at least as aero as Bigham's 0.15m^2 CdA during his hour record run to maintain 51.5km/h. Ganna was at around 0.18.

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