Thanks! One of the first quantified drag comparisons of aero helmets I’ve seen! Love to see ALL the MIT helmet data … still loved the guys contraption with the mannequin head in his apt. 
Despite its simplicity and relatively cheap price, the LG seems to be the standard for aero helmets. I think GTINGLEY tested it to be faster than the Giro Advantage (possibly by a bigger margin than you show here).
The seems like good news actually for the Bell, being so close to the best. I found the LG uncomfortable but love the fit of Bell helmets, hopefully they will bring it to the states.
I’m curious. With your confidence intervals overlapping so much - do you really consider that difference significant?
No, at least not in the standard statistical sense. OTOH, a difference in CdA of 0.002 m^2 would mean a difference in 3 km pursuit time of ~0.6 s, which at least in some cases can make the difference between winning and losing. Consider, for example, the results of the 2006 World Championships:
- Sarah Hammer (USA) 3.37.227
- Olga Slyusareva (Russia) 3.37.544
Sure, I wouldn’t argue that a difference of 0.002 m^2 isn’t significant. It clearly is.
I just think many people might look at your post and say, “Oh, the LG helmet is .002 m^2 less than the Bell and there is scientific proof!”
When in actuality, we are only 95% sure that the LG helmet is somewhere within 0.193-0.198 m^2 and 95% sure that the bell helmet is somewhere within 0.194-0.199 m^2.
I’m sure you understand this but I think that it could be easily lost by someone reading your post.
Andrew - you are on a roll today! thanks a lot for sharing and keep spilling the info before you change your mind!
I don’t suppose you have any info on the Giro Ad II?
literally seconds ago I picked up my latest shipment from trisports.com and lo and behold there was an advantage II in there…
“pay for my plane ticket, and cover the cost of renting the track”
had i not already made the purchase I most *definitely *would have taken you up on it but now of course I’d rather not know in case it falls behind the LG 
Andy:
My knowledge of aerodymanics coudl fit in a miniature thimble, so can you, in layman’s terms, explain what CdA and .0195 m^2 and .197m^2 means to the average person?
Thanks,
Bob
Not Andy either…
CdA is simply the product of the aerodynamic Coefficient of Drag (Cd, which is dimensionless) and the frontal Area (A) fo the objevt (typically measured in M^2).
Cd is basically due to the “shape” of the object (think of a flat board, versus a round ball, versus a wing shape, etc.), whereas A is simply the actual area.
Andrew… I know a kid that will smile with confidence when he checks your post.
You are an asset to this forum, congratulations.
Sergio
Andrew,
Did you do a test run without any aero helmet? That would be also very interesting.
Just great, first I am told by Trek data that I have a slow Scott Plasma TT bike, now this helmet data comes out and now I have a slow Bell Meteor to go with my bike. Boy, if I get much more data like this I will be going backwards…
Just great, first I am told by Trek data that I have a slow Scott Plasma TT bike, now this helmet data comes out and now I have a slow Bell Meteor to go with my bike. Boy, if I get much more data like this I will be going backwards…
Scott Plasma TT Rig
I hope you’re not running Tufos on that thing!
.
Thanks for sharing.
Thanks Andrew - was the LG Rocket an 08 with the new vent configuration?
Andrew,
Actually, I think this is really great data to have, the more data the better when making decisions and collecting information. I really was just trying to be funny with my comments, I still am a believer that the rider is what really matters and as long as you enjoy the bike, or helmet, or whatever other parts you put on your bike that is all that matters. For most of us we well never make a living on the bike, we just want to go faster then the last time we rode. Thank you for all the hard work you do to help educate everyone.
Glen
Hi Andrew,
I was wondering if you know where your Troxel fits in.
Stephen J
*I hope you’re not running Tufos on that thing! *
**
That is pretty funny because I stopped by the office of a fellow triathlete here and he was showing off his Scott Plasma. I was immediately thinking of the Trek white paper and then I noted that his Zipp wheels were shod with Tufos as well. I’ve never looked at a Plasma closely, but did so last night and it is not a stretch at all for me to believe that it is little faster than a Trek road bike. The head tube was massive and tubes were not really that narrow either. The down tube also looked fairly large and the shape was blunt at the front with the rear part of the tube sloping back flat without any curve. I didn’t have the heart to tell him the bike of which he was so proud was probably slower than plain, narrow round tubes and clinchers with good tires.
Chad
What size helmet does she wear? I have a brand new, medium 2008 LG Rocket Air (the one with the large vents) that I would have been glad to loan you for the tests just to have another data point, and I’m in the St. Louis area (O’Fallon). I also have a medium LG Chrono. I’m sure it’s not in the Rocket’s league, but… another data point. If you ever organize another round of testing and are interested in either of these, let me know.
Steve
Andrew, I meant a test run with a regular helmet (non aero). I have never seen data quantifying the aero advantage of an aero helmet vs a regular one. Thanks.
did you do any drag comparisons with the head tilted in different positions? I am curious how significant extra drag created by resting the neck is.