I’m trying to find some real aerodynamic drag numbers for aero bikes WITH riders. When I first started looking into this, I thought I’d see some data references just by looking at the ads for aero bikes, touting how aero their frames are compared to brand X. After skipping through the obvious marketing BS, all I could find are theoretical numbers and inconclusive wind tunnel tests. Any real data out there that I am missing?
Craig Calfee
not that i have seen but please test the p2-sl when you do :).
Thanks,
Dan
www.aiatriathlon.com
I’m trying to find some real aerodynamic drag numbers for aero bikes WITH riders. When I first started looking into this, I thought I’d see some data references just by looking at the ads for aero bikes, touting how aero their frames are compared to brand X. After skipping through the obvious marketing BS, all I could find are theoretical numbers and inconclusive wind tunnel tests. Any real data out there that I am missing?
Craig Calfee
I would be surprised if there were any real “reproducible” numbers on bikes with riders. The riders are such a big drag and it would be almost impossible to have them situated exactly the same for each run on each bike such that the numbers would have such wide variation they would show essentially no statistical difference between brands.
Here’s something that John Cobb wrote a number of years ago.
http://www.slowtwitch.com/mainheadings/techctr/frametube.html
HA!
Good luck with that Craig.
So you’re looking to get into “aero” frames? Don’t get me wrong, I’m one of your biggest fans, but we’re talking about TOTAL GEEKS here.
People post “bike porn” here all the time. It’s meaningless what the bike really does or how it rides. It’s all about the brand on the side and the look of the frame with the right build.
And for the record. I’d take a Calffe bike over anything on the market. ANYTHING. And I’m the guy who doesn’t give a crap. It’s all about the rider and the position. Once you get past a point in the quailty of the build, I think it’s moot what bike is between the riders legs. For now, I never pay more than 600 for a frame.
I can’t afford a Calfee and have been outbid on the last few I tried to get on ebay, but one day. One day, I too will have a calfee! For now, I’ll settle for the bike that fits. Trek, Kuota, Guru, QR, whatever. They’re all good bikes and I’ve spent time in the saddle of most of them. I’ve ridden an OCLV, Ritchey (only one close to the calfee) Cannondale, K2, Look, Litespeed, QR, Klein and a few others. All great bikes but the Calfee I had for a day was AMAZING!!! I was able to ride a tri one and a road one (owned by John Pellouchoud) for about 2 hours each in the mountains near his house in Boulder. (mostly lefthand canyon where he lives)
All I can say is WOW. You build one mean bike.
At least I have something to dream about.
Thanks.
Matt
PS. Oh yeah, get yourself a wicked looking aero frame with and without tri geo and you’ll be riding high. And update that website. DAMN! that site is wicked ugly. Keep up with the times bro! 
Would it be rude to ask if your interest has been sparked by Parlee’s recent showing at Interbike?
Absolutely no offense meant- I just often hear the two brands mentioned together.
I’m trying to find some real aerodynamic drag numbers for aero bikes WITH riders. When I first started looking into this, I thought I’d see some data references just by looking at the ads for aero bikes, touting how aero their frames are compared to brand X. After skipping through the obvious marketing BS, all I could find are theoretical numbers and inconclusive wind tunnel tests. Any real data out there that I am missing?
Craig Calfee
The biggest collections of wind tunnel data that I’ve seen stem from three sources:
testing done by Chet Kyle in the early 1990s and presented in various sources, including the old Cycling Science magazine/journal;
testing done as part of Project 96 a few years later and circulated in an Excel spreadsheet among certain parties; and
the famous aero bike “shoot out” conducted in 1994 or 1995 using Colby Pearce as the test subject, and published in various places, including VeloNews.
I’m too lazy to type in all the numbers for you here, but to give you an idea of what such results show: even with a rider aboard, a well designed aero frame reduces the drag of the bike+rider package by 5-10%, with the measurements themselves being repeatable to within approximately 0.5%.
PS: Another source of such data would be the several tests published by the German magazine Tour, in which they essentially use the “virtual wind tunnel” approach (i.e., an indoor velodrome plus a powermeter).
So what would Craig get by simply putting an aero downtube on his current line of carbon bikes? It could still be round at the top and bottom to ensure his current built molds stay the same. All he would need is some “squashed” round tubes 3:1 or 4:1 style.
SteveMc
Seatstays are also very important, as is seattube and seatmast, internal cables and headtube shape. Not just the downtube.
You’d have to contact Trek, Cervelo, Zipp and Kestrel. They’ve done their own wind tunnel testing but haven’t made the figures public.
I know all the other bits help but you have to start somewhere…
SteveMc
Seatstays are also very important, as is seattube and seatmast, internal cables and headtube shape. Not just the downtube.
You sound like a Cervelo ad : )
Seriously, I remember seeing the study Coggan referrenced and the frame (with rider - only tested one rider) avg. 8% less drag than round tubed (so the 5-10% he stated would be right on)?
I owned a Luna tri but it was just too big for me (ps Craig you need a 700c tri bike with a 55cm top tube). It was a great frame and I do lust after a bamboo one. However, I replaced the Luna with a (second hand) Isaac Joule not for the ride quality ('cos it isn’t as good but good enough for me) but because I wanted to ensure I had the “aero” angle covered. As they say, every little bit helps…
If Craig could make semi-aero frames without too much disruption (i.e. downtube and perhaps seat-tupe but without cutout, also compact frame for long aero seat post) then they would sell!! Which is after all what he does…
SteveMc
…and here is where it gets really exciting.
The realm of custom builders is a unique one as their production does not have to adhere to UCI rules if its intended end user isn’t bound by them.
Wouldn’t it be cool to get one of those new Parlee’s w/o a top tube or seat stays like a GT SBII? How about a custom Guru with aero tubes with a 6:1 aspect ratio? Could Craig build a bike narrower that the 25mm minimum? Two wheel sizes…
To have those options would be awesome.
I agree with everything in there except the part about a bike with no top tube being cool. It looks stupid, there’s no point to it, and I’d have nowhere to put my bento box.
But yes, I found the Parlee news exciting, and if Calfee follows him into the arena, that would be more exciting still. Would be great to see the innovation that kind of competition might produce. I think we’d see a lot of really great, really cool bikes result.
I went from a Trek to a Quintana Roo Lucero this year, I can honestly say that the QR is alot more aero. My bike times reflect this, fitness remained about the same. Tubing on the QR is much more aero than the Trek.
"I went from a Trek to a Quintana Roo Lucero this year, I can honestly say that the QR is alot more aero. My bike times reflect this, fitness remained about the same. "
LOL… a marketeer’s dream customer! Heaven forbid any other variables affected your speed like temperature, wind, humidity, road conditions, tire air pressure, sleep, food, and the hundreds of other variables that change constantly with the environment and the human body…
And after 17 Ironmans and more bike riding during races than you probably have total, I’m sure that never occured to him …
Hey, we all know it is about the engine, but the watts all add up: internal routing, ceramic bearing, aerobars, aero helmet, etc. Half a watt here, 1 watt there: over 112 miles equals some time now. Since 5 mins DOES matter to some trying to get to Kona, I’d say it matters. To many? Probably not, but marketing works on all levels for sure.
5-10% less drag for the aero frame over the round tubed frame sounds like a lot. How much drag is attributed to either frame in the overall CdA picture?
“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…