Marketing aside, The p3c has AWFUL aerodynamics. Don’t buy into the cervelo kool aid. It makes no aerodynamic difference how much a frame cut-out covers a wheel. It makes even less difference how close you can get the wheel to the frame. Horizontal drop outs don’t work.
In fact if your P3c is 54cm I'll do you a favor and take it off you free of charge. Good lord man, don't spend another minute with that silly cervelo bike.
Do a search for frame aerodynamics on the forum and you’ll get enough info to make you wish you’d never asked the question.
Hi gabbiev, I know you were looking for non-manufacturer feedback, but I thought I’d give you a little info on why our seattube-less frames are designed the way they are as it relates to your questions.
In terms of the leading edge of the rear wheel being exposed, you’ll notice that on our Airfoil Pro and its predecessor the KM40 Airfoil, the upper portion of the rear wheel is faired or blocked by the seat pod/seatstay/rear brake. That’s the part of the wheel that is moving forward relative to the frame, so it’s seeing a higher air speed/drag. The seatstay junction/wishbone on these Airfoil frames is purposely dropped down to maximize the fairing of the top of the wheel.
At the front of the wheel, the part that is “exposed” on these seattube-less designs, the wheel/tire is moving primarily downward, so the front of the wheel is seeing the same airspeed as the frame and rider. Since a good aero rim/tire combination is designed as an airfoil for bike racing speeds, it does not require a seattube to fair it or modify its shape (look for example at front aero wheels.)
A couple other things the no-seattube design does. First, it is really designed to work in conjunction with the rider in place and pedaling. That’s when the air is getting really mixed up, and needs to find a way through and around the rider/bike package. We’ve found the lack of seattube helps move the air through and past the rider’s moving legs, and provides cleaner air over that already aero shaped wheel/tire combo. We’ve shown great results on this in wind tunnel testing, with rider in place and pedaling. Another thing is the elimination of the seattube provides a smoother ride that you’ve probably noticed on your Kestrel. Hopefully, this equates to fresher legs and less body fatigue for the run.
So these are a few of the considerations that go into the design of our seattube-less tri bikes. Why doesn’t everybody do the same? - primarily it’s UCI rules. If you look at wind tunnel results comparisons from various sources, try to find tests where the rider was on the bike. Testing frames/bikes without a rider is a good design tool for the manufacturer, but does not tell the whole story for race day.
Best,
Preston at Kestrel
Good explanation. What’s the point of testing a bike without a rider.
What’s the point of testing a bike without a rider.
because kyle showed that deltas of bikes alone scale to bike+rider
g
.
The p3c has AWFUL aerodynamics
This is the first time I hear this. Care to elaborate more ??, any data to support this or any comparison to other frames ? What do you consider a good aerodynamic frame then ?
I am asking out of curiousity not fanboyism…
I’m gonna go out on a limb and say that rickn was being sarcastic, as the last line of his post was essentially asking the OP to GIVE him the bike 
.
Another question:
I’m gonna go out on a limb and say that rickn was being sarcastic, as the last line of his post was essentially asking the OP to GIVE him the bike
shhhh!!!
ya gotta let these things play out, man!
-c
Aww… my bad. I feel bad, cuz when I was new (not that long ago) I woulda been all confused too… its mean picking on new people 
When was that done and on what bikes? Perhaps the types and configuration of the bikes tested were similar to each other?
In the wind tunnel testing we did at San Diego last year, we found this not to be the case. The reduction in drag of our seattube-less design with rider in place and pedaing was four times what is what when compared without rider.
The press release details are here:
http://www.kestrel-usa.com/press/index.php
Then scroll down to this news item to download the pdf:
KESTREL BICYCLES IMPROVES PRODUCTS, ATHLETE’S RESULTS WITH WIND TUNNEL TESTING
-Preston
I love this quote because he bases these comments off the Airfoil’s success vs. a Talon SL…
I don’t doubt the Airfoil to be a decent bike, but I do doubt that it is any better than a P3c, Felt B2, Walser, TTX and so forth. My doubts come from comments made by Gerard, of cervelo, saying the TTX, Walser and P3c/P2C all outperform an airfoil. Any response?
We tested a few bottle/hydration options on the Airfoil Pro bike. I’d have to go dig up the drag numbers, but the bottom line was:
On race day, I would go for the behind-the-seat or in-the-aero-bar option, or both, before the downtube w.b. And again, this was on a no-seattube Airfoil Pro, so might be different for other frames.
-Preston
These tests were conducted to find out how much faster Macca could be on the Airfoil Pro. So it was compared to the Talon SL with all components and positioning held exactly the same. The results were significant enough to impress even the wind tunnel staff.
The next step will be to compare head-to-head with some of these other bikes - with rider in place and pedaling, equipment and position held constant. Everything must be very carefully controlled.
I’ve seen Gerard’s post, but have not seen any data on it. Nor am I clear that there were any head to head tests with rider in place. Would love to know more details.
Meanwhile, we’ve all seen where companies state or advertise that their frame is the fastest “UCI-legal” or is faster than certain other UCI-legal frames. My understanding is this is because those bikes did not do better than non-legal bikes like the Lotus and the Airfoil Pro.
-Preston
I recently purchased a Kestrel Talon and went two minutes faster over 30 kms at a local sprint tri than on my previous Cervelo P2K or QR Kilo.
I’m very curious as too how much more aero the Airfoil Pro tested compared to the Talon?
It is going to be difficult to find a non-manufacturer funded, independent wind tunnel test that accurately evaluates frame aerodynamics. Simply put, there is little motive for anyone to conduct such a test considering the cost of the test itself. Would you be willing to pay for the results? And ultimately, given the degree of cynicism that surrounds such “data” how likely would you be to regard such findings as conclusive?
My **sense **(i.e., unquantified **opinion **as a person who sells Cervelo along with other competing brands) is that the P3C is a good margin faster than other frames. Here’s one anecdote that has pushed me toward this opinion:
In 2006 I did the Ford Ironman 70.3 Whirlpool Steelhead Triathlon on an aerodynamic carbon fiber frame from a high quality brand. The bike was good and I averaged exactly 23 m.p.h. for the 56 mile bike segment. I suffered pretty heavily on the run because it took quite an effort to manage 23 m.p.h. on the bike. I finished around 5:05:00. Long, tough day.
In 2007 I did this same race on a Cervelo P3C with a similar wheel configuration, the same clothes, etc. I rode easy, and I mean an honest 65% effort ('06 was a 90% effort). My bike split was 22.9 m.p.h. I ran over six minutes faster. I had done less run training.
Bottom line for me: The P3C was one of the factors that contributed to a faster, easier race.
As a result, I’m using it at Wisconsin.
cerveloguy (or is it now kestreldude?),
The Airfoil Pro does quite a bit better than the Talons in the tunnel. (After all, it’s designed to.) About a minute faster over 40K at the 40kph/25mph tunnel speed.
That’s with the same equipment and rider position, but the Airfoil also allows you to go steeper and lower than that, of course.
Also the no-seattube design makes for a very smooth ride, which can’t be bad for your run.
-Preston
It wasn’t aerodynamics considerations why I switched to the Talon. It was because I wanted to ride less steep for comfort reasons. I’m probably at about 76 degrees and now my crotch and neck aren’t aching like they did when I rode steep. I was actually surprised to find that I rode faster this way. I like my Talon so much that I’m considering eventually getting another, one for road and another set up exclusively for tri.
Ah yes, cerveloguy, we’ve followed your posts (not-so-Big Brother is watching) and we support your right to choose!
I don’t want this to turn into a sales pitch, so e-mail us at Kestrel if you want more details, but if you’re riding at 76-degrees you could look at the Airfoil Pro as well as the Talon SL. Both are a step up from the Talon in various ways.
-Preston
Meanwhile, we’ve all seen where companies state or advertise that their frame is the fastest “UCI-legal” or is faster than certain other UCI-legal frames. My understanding is this is because those bikes did not do better than non-legal bikes like the Lotus and the Airfoil Pro.
I think you have to be careful assuming that. If you are pitching to protour teams, then it is important to assess the competition. There are, for example, a lot of things that can be done within the UCI parameters to make a bike more aero than the competition that are not always present on a non-UCI-compliant design. The first three that I’d name would be:
So, I actually don’t find the UCI restrictions to be as limiting as some people say. It is somewhat lore that a non-UCI bike will be faster than a UCI-bike. I say that because I’ve never seen anything that proves this. Look at Burrow’s monoblade fork. The monoblade fork actually tested worse than a traditional fork because the extra material required to make the fork strong enough to withstand the unique loading increased frontal area too much. The monoblade fork MIGHT have been faster if it could have been made strong enough with less material, but that technology did not exist at the time. Which gets us to what may actually be at the heart of the whole debate. A two-triangle design is a tremendously strong shape from strictly a structural standpoint. So, when you get into the limitations of existing materials, then you may end up with a limitation there. I.e., it is entirely possible that you need a minimum of X-grams of carbon fiber to make a frame that is structurally sound. And ultimately, the best possible design that utilizes those X-grams of carbon may very well be a double-diamond, or that at least, you can’t (with today’s technology) make a frame that is faster than a double triangle given that you need to use a certain amount of material. Put another way, why is the Airfoil Pro not substantially lighter than a bike with a seattube? I think, though accurate frame weights are notoriously hard to come by, that it is certainly among the lightest TT frames, but not measurably lighter. The answer, I think, is that you needed to move the material you took away when you removed the seattube, and had to put it somewhere else. And, it’s been suggested (not by me, though I may agree) that the redistribution of that material ultimately can negate the benefit of chopping it out in a particular place.
Now, this isn’t always the case, since by you own calculations, the airfoil beat the Talon (though the frames aren’t identical in terms of tube shapes except for the missing seat-tube, are they?), but the talon is not necessarily the “best in class” UCI-legal TT bike. The Softride is a rather extreme example. Look at how thick the downtube section of that bike is (and I’ve heard it was still quite poor in terms of lateral stiffness, a criticism that I have not heard about the Airfoil). There is no way, with current technology, that you could have made a softride with a P3C downtube that would have been rideable. You needed to make the bike stronger. Would it be possible, for example, to have even made the Airfoil out of aluminum? I tend to think not. And carbon represents a wonderful material for making a bike that can handle the load of frame that does not have a truss (if you think of the double-triangle design as a diamond with a cross-truss), but you do need to make it differently. It is certainly possible that it might be faster, but I don’t think you can take it for granted. The Lotus was (and is) a very fast bike. But it’s not obvious that violating the UCI’s aspect ratio rules is a good thing. You could very easily make a tube with a huge AR that was very deep (which would probably sell very well). But it would probably stall at quite low yaw angles, and perform quite poorly. I believe Josh from Zipp spoke about this regarding rim depth. There is a reason the 808 is 81mm deep. They chose not to go deeper for a reason. Of course, deeper sells wheels, but I haven’t seen any data showing that the 90mm HED Stinger or 100mm Blackwell thumps the 808. I’ve actually not seen any data that even shows it beats the 808. But I guarantee if I made a 110mm wheel, it would sell, regardless of performance. I think this same logic can apply to a non-UCI bike. People assume it is faster, but why? The assume the double-triangle frame is a limitation, but is it really?
There continue to be rumblings of “independent” tests comparing all these frames. But they have yet to materialize. It’s left to people to test their own. I will say that I know of a bunch of riders who’ve been to the tunnel who choose to ride the Airfoil, and I think that says a lot. And Macca did set a PR on his Kona marathon after making the switch to the Airfoil (did the watts saved, even riding in the front group, give him fresher legs? It’s very possible). But the test was not you sitting him down and saying “let’s put you on the fastest bike available.” It was you saying “let’s put you on the fastest Kestrel available.”
I think the Airfoil is a very aerodynamic bike. I don’t think that the fact that it does not conform to UCI requirements gives it an inherent advantage though.