## Let's play a quick little game. Guess the watts.

Moderators: robbosmans, Moderator Team

## How many watts to hold 32mph/51.5kph Additional details below.

250W-
2
2%
300W
5
6%
350W
11
13%
400W
18
21%
450W
22
26%
500W
14
16%
550W
12
14%
600W
2
2%
650W
0
700W+
0

TobinHatesYou
Posts: 11198
Joined: Mon Jul 24, 2017 12:02 pm
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.
Last edited by TobinHatesYou on Sun Nov 27, 2022 4:26 am, edited 1 time in total.

maxim809
Moderator
Posts: 765
Joined: Sat Feb 25, 2017 6:28 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.

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

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TobinHatesYou
Posts: 11198
Joined: Mon Jul 24, 2017 12:02 pm
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

maxim809
Moderator
Posts: 765
Joined: Sat Feb 25, 2017 6:28 am
there's not much more to say, i know

Karvalo
Posts: 2949
Joined: Fri Aug 10, 2018 6:40 pm
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?

spartacus
Posts: 910
Joined: Mon Apr 04, 2011 6:53 pm
385 watts

bikeboy1tr
Posts: 1242
Joined: Thu Mar 21, 2013 3:19 am
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.
viewtopic.php?f=10&t=154188
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Chaunch
Posts: 24
Joined: Tue Jun 01, 2021 12:10 pm
When do we find out the correct answer?
What do we win?

TobinHatesYou
Posts: 11198
Joined: Mon Jul 24, 2017 12:02 pm
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.

robeambro
Posts: 1671
Joined: Sat Jul 07, 2018 6:21 pm
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..

calleking
Posts: 359
Joined: Sun Sep 13, 2015 3:20 pm
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
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CustomMetal
Moderator
Posts: 1070
Joined: Sat Dec 01, 2018 4:14 pm
Location: UK
I do that easily on my TT bike at 300 watts so I think 350 for the road sounds about right
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Karvalo
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Joined: Fri Aug 10, 2018 6:40 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.

CustomMetal
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Location: UK
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
Allegra- Steel Lugged (coming)
Alya- Hill Climb Race 4.84kg
Bertha- TT
Perdita- Turbo bike 8kg
Serenity- Ti Gravel 9.5kg
Verity- Ti Aero (coming)
Wilda- Climbing Bike (coming)

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TobinHatesYou
Posts: 11198
Joined: Mon Jul 24, 2017 12:02 pm
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.