With wind tunnel tests, velodrome tests and field tests it’s becoming more and more common to see CdA statistics being quoted. On here I often see triathletes quoting CdA stats of 0.2-0.22, which from what I’ve seen is smaller athletes with refined positions and good equipment.
Using bestbikesplit I have begun trying to get some baseline data which I can hopefully improve on. My initial efforts indicate in the range of 0.27. For context:
47 year old male
6’2" (188 cm) 180 lbs (82 kg)
56 cm 2007 Cervelo P3C
no risers, low profile aerobars, 130 mm stem
non-aero spokes training wheels used in baseline testing (race with old narrow toroidal Zipp 404 and disc cover)
standard vented helmet (race with long tail Spiuk)
Im not sure how accurate the intial 0.27 data points are but I am sure that as I collect more data and get more experienced I’ll have more reliable baseline data and will hopefully improve on it.
Out of curiosity what is a good CdA for a 6’2" (188 cm) or taller triathletes shoot for? What kind of #'s would Jordan Rapp, Torbjorn Sinballe, Bjorn Andersson or Slowtwitch poster Eric Reid get for CdA?
I’m 6"2’, 180 lbs with wide shoulders and the best I have done with BBS aero analyzer is 0.25. I was put through the Stac virtual wind tunnel and there were no obvious improvements to be made other than tucking my head more. I’m thinking i’m close to my limit without actually going to the wind tunnel.
What kind of #'s would … or Slowtwitch poster Eric Reid get for CdA?
great, another opportunity for eric to post that random oblique shot of himself in the wind tunnel…
you’re gonna get numbers that are all over the place. what you should shoot for is a position you can hold that minimizes waste. some of the posters that have responded may be aero, but that says nothing about their overall race results. the important time is the finishing time. be as aero as you can be to be efficient but sustainable, and run fast.
…what you should shoot for is a position you can hold that minimizes waste. some of the posters that have responded may be aero, but that says nothing about their overall race results…
I agree with you a comfortable and efficient position is necessary. A position that tests well but is unsustainable on race day is meaningless. My subjective assessment of my self, is that my current position is comfortable and can ride in the aerobars as long as I want to.
You are absolutely correct that race results are what matters. Race results are what I am shooting for. My Ironman PR was in 2009 at 38 years old in 9:56 with a 5 hour flat bike split on a Cervelo P2SL, my wired PowerTap had unfortunately quit working earlier in the year, so no data to compare. My goal is to try and go sub 10 again in 2021 as I enter M50-54. Older with slightly nicer equipment. Bestbikesplit is a great tool that can potentially help me achieve my goal. Assessment of and improvement of CdA can be helpful in trying to beat father time. Just trying to gain context on good values of other triathletes of similar size.
barring any mobility/structural issues, you should be able to achieve something like .22 - .23 without going on a crazy spending spree. height is less of an impact to cda than is width.
I’m 5’11" and 83kg my cda is 0.21 in a skin suit and aero helmet. I might be better on race day with my H3 on the front and faster tyre than on my Mavic training wheel. (garmin hub speed sensor)
I’m sort of lucky as I have 31’ legs so I sit very low and long on the bike.
Clearly some of those bits won’t transpose nicely into Triathlon, the overshoes in particular, but the rest (except the helmet which is basically just guesswork unless you get yourself tested) would be a good starting point for someone of a similar build.
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I decided to write a blog on my journey and process of improving my aerodynamics. I have some pictures showing a historical perspective of my position as well as current position as seen on a trainer. Any feedback is welcome.
Your head looks lower than your back. Might be able to put out more power for equal or better CdA if you raise your front end. Also, your shrug in your pics of you on the trainer is much better than the one in your race pics.
Never ridden the mantis position shown just took a couple pics of it out of curiosity since it seems to be gaining popularity and supposedly tests well for many.
The position with more level forearms is essentially the position that I’ve been riding since 2006. I feel comfortable and have no difficulty holding it as long as desired. Believe it or not, prior to 2006 I experimented with significantly more drop and trial error brought me to current position which I find quite sustainable.
I had assumed that my current position was probably fairly aero, but I am starting to wonder.
Thanks for the feedback. I have been practicing “turtling” my head and neck for significant sections of each training ride for the last several months. I never even though about it during the time period that those race pictures were taken.
The steer tube on the bike is cut all of the way down. I have a pair of Syntace aero bars which are a high stack bar. I can see how these look and feel.
