Aerodynamic Head Position in Cycling

I'm taking a brief break from brittle bones to write about other topics. My next posts on bone health will have to do with what the reserahc suggests is effective. Turnsa out that there is a lot of research to read on this topic. In the mean time, the Paris-Nice stage race is being contested in France and Versus television is covering it here in the States.

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Last night I watched the March 11 Paris-Nice Time Trial which Tony Martin (HTC-Highroad) won taking the yellow leader’s jersey from Andreas Kloden (Radioshack). I have no way of knowing for sure, but I suspect the difference (46 seconds) between the two finishing times was more a result of aerodynamics than power.

It’s obvious that Martin has devoted a good deal of time to getting his position dialed in. Even though Kloden’s back is much flatter, Martin’s rounded back is not a problem. The wind will be escorted over it and off the trailing edge rather smoothly. The thing that Martin does best, however, is keeping his head out of the wind. This isn’t easy to do but the pay off is significant. I’ve written about this before (Feb 2007, Feb 2010, December 2010).

The accompanying pictures were taken from the television and so are a bit blurry (click to enlarge). The first is a sideview of Martin showing his rounded back. The second is of Kloden. Kloden’s much flatter back is evident. But in these two pictures notice how much lower Martin’s head is. A high head position could slow a rider by more than 1%. The difference of 46 seconds amounts to 2.24% of Kloden’s time.

To get your head into the position Martin has his in in the above picture requires pointing your nose almost straight down and then rolling the eyes up as if looking over your sunglasses. This takes some getting used to. Both your neck and your eyeballs will fatigue unless you do it frequently. They can be trained just as your legs are. Here in the third picture you can see a picture of Jani Brajkovic (Radioshack), another excellent time trialist, in a head-on shot. Notice that his chin is below his chest and that the top of his helmet is about even with the top of his back. He’s looking “over the top of his sunglasses.”

But Martin did something else, mostly early in the race, that I believe reduces drag even more. He further lowered his head and looked straight down at the ground briefly 10 or more times a minute. This further reduces the drag created by the head as it is then completely below the back. The small helmet tail sticking up creates insignificant drag compared with the much larger head in the lowered position reducing drag significantly. You can see a picture of it here. My December visit to the Fort Collins, Colorado wind tunnel, along with the guys from PowerTri, suggested that this head-lowered position saves another 1% or more. I never saw Kloden look down once. He kept his head in what is considered to be the traditional time trial position as best he could as shown in the last picture.

Be aware that looking down is dangerous. A friend of mine has been in a wheelchair since 1987 because he was riding in this position and ran into a vehicle. The way Martin did it was perfect. He looked down for just a second or two at a time but did it repeatedly. The best times to do this are when you are going downhill or into a strong head wind.

Also, getting your head into the below-the-back aero position (not even the more aggressive head-down-helmet-tail-up position) is not going to work for everyone. The longer your time trial the more challenging this becomes. For example, in a half or full Ironman-distance race the very aggressive position used by any of these three riders is probably not going to work. Neck, back and eyeball fatigue will be too great causing you to come out of the aero position repeatedly, especially later in the race. That will “cost” you more time overall than simply having a more comfortable position. It may even be overly challenging for races lasting an hour or so. But if you’re time trialing for less than an hour and you need to shave a few more seconds off of your time to be competitive then you might give it a try. That requires training on your TT/tri bike frequently working on position.

The starting place for this is a bike fit by a professional fitter. Making changes to your position to become more aero without taking into consideration how those changes affect the other aspects of your pedaling technique and position is as likely to slow you down as to speed you up.

Comments

[Ed (the real one)]

It strikes me that a major safety (and aerodynamic) improvement would be a mirror at 45 degrees that would let you look forward while your face was pointing downwards. A sort of "front-view mirror". It could be attached either to head or bike.

[Mike Hardy]

I think it's possible to add a couple more tricks to this as well by stacking hands. This both narrows the very front of the rider to more of a wedge, width-wise, as well as - if they lower their helmet using the technique you describe to nearly meet their hands - vertically. Here's an example from Ben Jacques-Maynes during a blazing TT, and I've seen Zabriskie do it as well: http://hcphoto.smugmug.com/DBC-and-NorCal/MercoCUCyclingClassic/Merco-2011-P2/16083080_wWDqc/1/1207712862_AZz6k/Medium

I haven't seen anyone using the skinsuit with "wings" ("extra" accidental I'm sure fabric between upper arm and ribcage creating armpit fairings) that Zabriskie used at the end of last year though

[Jgdicker]

Joe, John Cobb said that the tail sticking up is a problem. He designed the Rudy Wingspan helmet with the "chopped" back to deal with this issue. The back is similar to the aerodynamic rear end of the Toyota Prius.

[Joe Friel]

Jim--John is the one who first told me it wasn't a problem. I asked him that in a talk he did a couple of years ago. And re-asked it to make sure I got it right. We later confirmed that he was right in the wind tunnel. Less drag with head down and tail of helmet up. So I don't know what's going on. Need to ask John, I guess.

[leighton]

hi joe a couple things strike me about this tt i too enjoyed watching.

i think martin's general mass and cda is greater than klodens, as they're seat to tri extension ratio, look very similar i.e. level with the headset.
i think he over comes this(>mass)with power.........i'd love to know what they both put down and watts per kg.
with all the pro wind tunnel reseacrh, the slighter rider should be more aero dynamically sound?

[Brian]

Hi Joe - I love your blog and your books, they've been helping me take my training to the next level for years. This aerodynamics post coincides perfectly with a "problem" I am trying to figure out, namely I seem to be able to put out some fairly decent power numbers, but can't seem to get my speed results to match up to them. Here is the scenario: I live in Coeur d Alene, can avg 290 watts for at least one loop of the Ironman course (I weigh in at ~77kg), have had my bike fit, but seem to be infinitely mired right at 5 hour pace. The hills seem to be where I lose most of my speed (my avg on the flats is around 23.5-24), and I even increase my watts in the hilliest sections to around 310-330 to try to compensate. I know more info is probably needed, but where would you start troubleshooting my plateau (best IM Cda bike split is 4:55, worst is 5:00, avg watts for the 5:00 on a closed course were only 245). Is it a combo of my aerodynamics and weight, or do I just need to lose some weight, or up my power in the hills even more? I'm ambitious and desperately want to be closer to 4:50...

[Joe Friel]

Brian--I wish I could tell you. There are many, many variables here. You mentioned one of the biggies--body weight relative to weight. Not always a limiter, tho. I once coached a 90kg IM athlete (very tall) who did 4:55ish in Kona. We focused on him being as fit as possible for the bike and then held back a lot on the ride. I think he could have done 4:45 there but then he would have walked a lot.

[Nathan]

Joe, I've accompanied John on his trips to the tunnel the last 2 years, so perhaps I can shed some light onto the head down, tail up question. There is a trade off to this, as in, a head down position will get your head in line with your shoulders/back and thus reduce your drag greatly. And despite the tail sticking up, the trade off is still a benefit because of the reduced frontal area. If you want to discuss this further feel free to contact me.

[Jgdicker]

Very interesting. About 16 months ago, he fitted me. I wore my old long tail helmet for the fitting. He said that my head position with the tail sticking up was a problem, and suggested that I buy the Wingspan. Since that time, I have read other articles that suggest that the "Prius" rear end is very aero. If I am not mistaken, this applies to the shape of tubes as well.

[Nathan]

If you're a head down guy, then of course a shorter tail would be better than a longer tail. Ideally, you'd "turtle", but as Joe pointed out, that can be hard to do for long distances. The Kamm shape is aero when it applies to tubes, but is used because of the 3:1 UCI rule, not because it's the most aero shape. (See Trek Speed Concept)

[Jameson-king]

I thought I'd throw in an example. I am with PowerTri and was at the wind tunnel when Joe attended with us a few months ago. A good example is that the Spiuk Kronos aerohelmet, with its long tail, is not so efficient when the rider has his head down. If you can get more of the frontal surface area below the shoulders (like having your head down), then it is usually an advantage. The compromise of putting your head down it having the tail sticking up, but this is still less frontal area above the shoulders, than if your head were up.

[Rob Morris]

Is it not fair to say though (i do agree with comments by the way) that with Martins position on the bike slightly more upright, he is utilising a much more powerful gluteal activation? The Austrailian pursuiters have proven on the track that actually, that low profile position is not always the best solution if it sacrifices power output? Just a thought

[Jeff Harmon]

Hi,Joe.
Great article.
Can you speak to the issue of elbow width and aerodynamics?
I have my elbow as close together as is comfortable, which I thought was better for short distances, but I notice that many of the pursuit racers use a wider bar position.
Thanks.

[Joe Friel]

Jeff Harmon - In theory a narrowed elbow position will improve aerodynamics. In practice it doesn't always work as it _may_ reduce chest capacity thus restricting breathing and for very long events (IM for ex0 it can be very uncomfortable causing the person to frequently come out of the aero position thus compromising aerodynamics.