How many watts at 20MPH?

it took me 290watts to average 22.3mph on an 8 mile course that had 400 feet of climbing on slight grades, with a 10mph headwind half the time.
thats standard road position, no aero gear. i am 6'2" 170lbs.
also, it was 45 degrees, and at sea level.

its kinda odd, but i havent really tried to determine power requirements for certain speeds yet. i will when i get my bike out on the roads again.

also, cadance has no effect on power.

Interesting!

How did you measure that?

I guess that is an average wattage?

Quoted post said:

Originally posted by Whitney
Interesting!

How did you measure that?

I guess that is an average wattage?

I've heard from some that this site is pretty accurate, but I can't give any thought to it myself as I have no means of measuring power.
http://www.kreuzotter.de/english/espeed.htm

Whitney, here's a good site to answer your question:

http://www.analyticcycling.com/

i have a powertap pro

analyticcycling.com is not very useful in determining power for your speed on flat ground, because it is very hard to figure out what your frontal area is. the site is useful for climbing if you know the exact gradient of the hill.
got to www.topozone.com for topo maps of the US

Quoted post said:

Originally posted by velomanct
analyticcycling.com is not very useful in determining power for your speed on flat ground, because it is very hard to figure out what your frontal area is.

This isn't a failing of Tom Compton's calculators, but simply reflects reality: if you don't know your effective frontal area (product of coefficient of drag, Cd, and frontal area, A), then you can't calculate the power required to overcome aerodynamic drag. If you know what you're doing you can probably come up with a reasonable guess for CdA, but the resultant power/speed estimates are just that: ballpark estimates.

This also points out how important a good aero position is to achieving and sustaining speed on the bike. To illustrate, I was riding this weekend with a buddy with almost the same bike as mine, and about the same weight. On a downhill, I noticed we were coasting side-by-side at identical speeds, while both on the drops. Halfway down the next hill, we were again dead even at about 30 mph when I tucked my arms in under my chest by grabbing the bar right next to the stem. This change accelerated me immediately and I pulled away at maybe 2 mph faster....it was that dramatic a difference.

hey, thanks for the sites and info.

I have run our guy through the models, tried to keep everything the same, but came up with

130W for the Kreuzotter, and

170W on the Analytical site

Which seems fairly different to me.

It's interesting though, anybody got a SRM I could borrow?

Whit

Oh Yeah, as far as aeordynamics goes, I have in interesting quote from Jeff Broker, Chief Biomechanist w/ the US Olympic committee:

"Aerodynamics will make you faster than perfect pedaling style...Wind tunnel results show that eliminating 10 grams of drag saves 158 feet in a 25 mile time trial. How much is 10 grams? It's the drag created by projecting about four inches of a pencil into the air stream. That baggy jersey or upright riding position is costing you minutes."

This is also one of the guys who introduced the SRM power meter in the States.

Whit

Quoted post said:

Originally posted by Whitney


I have run our guy through the models, tried to keep everything the same, but came up with

130W for the Kreuzotter, and

170W on the Analytical site

Which seems fairly different to me.

IWhit

Using your weights, 0% grade, and defaults for the other parameters, analyticcycling.com gives me 137W @20mph. Did you change any other parameters besides weight.

Quoted post said:

Originally posted by asgelle
Using your weights, 0% grade, and defaults for the other parameters, analyticcycling.com gives me 137W @20mph. Did you change any other parameters besides weight.

D'OH!

Actually, I got the 130 on Analytical, and 170 on the other site.

And there are so many variables on the other site, that I am not really sure if I am comparing Apples to apples anyway.

Fun to play with tho.

Whit

Although not applicable to the road, what about wattage at different speeds on a trainer like the CycleOps Fluid 2?