5-10% less drag for the aero frame over the round tubed frame sounds like a lot.
Yet that’s what direct measurements reveal.
How much drag is attributed to either frame in the overall CdA picture?
Standard practice is to test a frameset with wheels, probably in part because the fixtures used are designed to work with complete bicycles. Anyway, a really good aero frameset (plus wheels) might account for ~20% of the total drag, with the wheels and frame each being roughly half of that (based on wheels tested in isolation).
“more bike riding during races than you probably have total”
Oh gawd… are you KIDDING me?! I love how you don’t even know who I am yet feel like you’re some expert on how many miles I ride per year… regarding your claim: that’s a rather childish schoolyard claim and also so far from being possible it’s ridiculous…
Actually, the analogy comes from the U.S. Army and not a “schoolyard” - and yes I was “kidding you” (and I know it is not likely TRUE, nor am I an “expert” as I don’t know you nor Barry much either - but I’d offer an educated guess that you have not ridden as much as him nor finished 17 IMs).
The analogy is usually for a young Lieutenant (me many years ago): it basically says that the Platoon Sergeant has more time in the chow line than you (the young LT) has in the Army. Analogies are useful to some, lost on others …
All I’m saying is that my bike riding and racing have been consistently much faster this year than any year in the past. You listed alot of variables, but you did not list age. I am not getting any younger (46) and I have to rely on technology to keep up with you young, fast bastards
I’ve seen data similar to what Coggan posted in my own experience, which was based on trend averages from a whole lot of SRM files. I usually ballpark it to be at least 1-1.5kph @ ~40kph, which works out to 2.5-3.75% faster. I would be able to make more comparisons based on two years worth of data, but I only have about 3 months on my round tubed bike and QR where the positions were virtually identical. Prior to that on my round tubed bike I rode with less drop, and more recently on my QR I run more drop. But there is a good period where I rode with virtually identical drop. Some equipment changes - different aerobars & wheels. Tires were similar (but not identical) ProRace2 25mm vs. Krylion Carbon 23mm) with same innertubes (Continental Race Butyl). Given the data Kraig Willett has posted on those items, I am confident that the difference in frame aerodynamics is still statistically significant, especially since I did my training with two in-frame bottles on both bikes, which will offset the aerodynamic differences of the frames somewhat. In any case, my own experiences and SRM files support the data out of the windtunnel.
5-10% less drag for the aero frame over the round tubed frame sounds like a lot.
Yet that's what direct measurements reveal.
How much drag is attributed to either frame in the overall CdA picture?
Standard practice is to test a frameset with wheels, probably in part because the fixtures used are designed to work with complete bicycles. Anyway, a really good aero frameset (plus wheels) might account for ~20% of the total drag, with the wheels and frame each being roughly half of that (based on wheels tested in isolation).
so splitting the difference of 5 and 10 percent yields 7.5 percent reduction due to aero tubes. If the frameset + wheels = 20% and the wheels and bike each contribute 10% of total drag, a round tube bike would cost you .03lbs of drag. For the calculation assume that the rider has a good position with 3.8lbs of drag at 26mph for the bike + rider (aero framed bike).
Josh at Zipp has said .1lbs of drag = 6 watts, so .03lbs-force would equal 2 watts. 2 watts? Is this it or does my math have a major malfunction? How much time would be saved by 2 watts?
While a bit outdated and certainly not as scientific as can be, Cat Bikes tested their Cheetah along with some other bikes on a velo track several years back. It’s surely not the comprehensive test that you are looking for, but may be somewhat interesting nonetheless.
All I’m saying is that my bike riding and racing have been consistently much faster this year than any year in the past. You listed alot of variables, but you did not list age. I am not getting any younger (46) and I have to rely on technology to keep up with you young, fast bastards
I might be more likly to believe you if you didn’t feel it was necessary to name the bike brand and then list that you get a deal on their bikes on the bottom of your page; But i’m sure your unbiased.
FYI I have ridden many IMs with times between 4:58 and 5:15 on a road bike with clip on a tri bike and a “aero” road bike with SRM, on the same course and the time differences didn’t display any statictical sig’n.
Your math is off. 10% of 3.8lbf is 0.38lbf, NOT 0.03. So, yes, saving .1lbf of drag is roughly 6 watts. (.1lbf = .44newtons, then just multiply that by speed in m/s to get wattage).
So .38lbf = 1.69newtons. At 11.6m/s (26mph), that would save 19.6 watts. The 6watts for 0.1lbf number comes from 30mph.
So basically, you were a decimal place off. So, an aero frame saves ~20watts at 26mph. Not at all insignificant.
The cheetah tests seem to suggest more in the range of 5 watts and that is from Storcks(which I’m guessing are round tubed) to Cheetah(about as aero as one gets). I’m guessing with the addition of yaw the wattage would be more in the 10 range
I have a question for you: how important do you think aerodynamics are when you’re going 25 mph? If you could go the speed of a Stealth bomber, then maybe it does.
I built the very first aerodynamic bicycles in 1979. Reynolds tubing in England made the tubing with my design. That year, on my aero frames, the US Pan-American team won the 100 km Team Time Trial, and Greg Lemond placed second in the individual pursuit at the Junior World Championships in Argentina.
After all of this and the following decades of aluminum, titanium, and carbon-fibre aero frames that have become increasingly perfected, I have come to the conclusion that aerodynamic frames MEAN VIRTUALLY NOTHING at the speeds bicycles reach, and, in many cases, are actually DETRIMENTAL, when wind conditions are not favorable.
The results of these riders who rode the very first aero frames, as well as all of the riders who use them today, are a result of proper training techniques. Period.
Mike Fraysse
I would guess that yaw angle is the major factor there. Remember 5-10* is normal yaw angle. Coggan also has said in other threads that the Colby Pearce test, done at TAMU, (which I cannot find online) showed the CAT Cheetah testing worse than several of the frames that it best in the TOUR test. In any case, I would say that the wattage differential between the bikes TOUR tested would have been much different at 5-10* of yaw, giving a figure much closer to the 20 watt number I cited.
I am just trying to figure this out, not pointing fingers.
ErnieK split the difference with 7.5% for the reduction in drag of an aero tube over a round tube. Now if 10% of the total drag on a bike/rider/wheels is the frame and that total drag is 3.8lbs then 10% is 0.38lbs, but of that 0.38lbs only 7.5% is the difference between aero and round so 0.03lbs is the drag difference, right?
I am just trying to figure this out, not pointing fingers.
ErnieK split the difference with 7.5% for the reduction in drag of an aero tube over a round tube. Now if 10% of the total drag on a bike/rider/wheels is the frame and that total drag is 3.8lbs then 10% is 0.38lbs, but of that 0.38lbs only 7.5% is the difference between aero and round so 0.03lbs is the drag difference, right?
Ouch, my head hurts… It’s not 7.5% of 10%. Coggan said 20% for frame + wheels. Assume that they tested the aero frame and regular frame with same wheels to get the 5-10% number. So we split the 5-10% to get 7.5%. So you can choose, either 10% OR 7.5%. So 0.38 OR 0.29. But it’s not 7.5% of 10%, which is the math you are doing.
Don’t overthink it. Here, we’ll start from scratch.
BEST wheels and frame have equal weight:
– Aero frame = 10% savings
– Aero frame = 3.8*0.1 = 0.38lbf drag saved
Not all aero frames are equal:
– BEST aero frame = 10% savings
– OKAY aero frame = 5% savings
– Split the difference = 7.5% savings for “average” aero frame
– Average aero frame = 3.8*0.075 = 0.285lbf drag saved = 0.3lbf drag saved. (You can convert to newtons and figure out watts from here.)
It’s just a decimal place error.
It’s not that aero frames save 10% and of that 10%, only 7.5% is from aero tubes. That is not what is being said. If you want to start breaking down wheel-cutouts, etc., you can, but those are much less of a factor than the tube shape (case in point being something like the Hooker, or go to Cervelo’s site for the marginal difference between a P3C and P2C). So assuming that 7.5% of TOTAL drag reduction from an aero set-up (wheels & frame) is due to aero tubes is very reasonable. But not 7.5% of 10%, which would net out to only 0.75%, which would be basically meaningless…
