Monday, March 18, 2013

Wind Tunnel Vision

I’ve always liked the phrase “it doesn’t get easier, you just go faster.”  Put in the hard work and reap the benefits.  Part of that hard work, though, is understanding that there are things you can do to create speed without having any physical gains.  Free speed.  I haven’t met an athlete yet that doesn’t love it – but just like physical gains, you have to think and work for it.

How do you go about finding yourself some free speed?  Simple things like keeping your drivetrain clean and oiled can help reduce the mechanical drag from dirt and grime.  Finding a comfortable saddle so that you’re still and steady on the bike is key.  In fact, my friend James Haycraft , aka “The Pro”, wrote an excellent article on this topic.

Of course, athletes can always do what I did: marry a beautiful and wonderful woman who gets your desire to go freakishly fast, and get you the greatest Christmas/Birthday combo present ever: a trip to the A2 Wind Tunnel in Mooresville, NC.  I’ll take a moment to let the awesomeness of this gift wash over you.

Before I get ahead of myself, this requires two points of explanation: 1) I was in the market for an aero helmet and, 2) I’m a dork.  The latter point helps to explain the former and the lengths I went to figure out which helmet to select.  Trying to determine the optimal helmet for myself was a major dork-a-palooza.  During the “offseason”, I researched and read about every helmet from the Giro Selector to the Lazer Tardiz.  I mean, I created a spreadsheet and cross referenced characteristics to find the optimal helmet.  (Yeah, so like I said, I’m a dork).  But as much information as I could immerse myself in, it was all hypothetical: I couldn’t know for absolutely certain what helmet would work the best.  So, I made a choice and wrote a note to Santa Claus – obviously.  Fast forward to Christmas day and my awesome wife is handing me a gift certificate for A2. I took my helmet from Santa back to the store with a smile on my face.

When I arrived at the A2 Wind Tunnel, I was ready to listen and learn.  This team at the tunnel had recently hosted Craig Alexander, Mat Steinmetz, and the Specialized team – the best thing I could do was ask intelligent questions and soak it all in. They were going to tell me real answers to all those hypothetical questions that I had posed during my helmet research.  Dave Salazar, the manager, and Jim O’Brien, the bike-fitting guru, were on-hand to walk me through the process and answer all the questions that I had (which were a ton).  They got me set up in the tunnel and had me begin to spin so that Jim could take a look at my present position to determine some adjustments that could be tested.  While my #1 goal was to find an aero helmet, I knew I had an opportunity to make some tweaks in the position.  After the warm up, we needed to develop a baseline from which we would compare/contrast all other tests.

Now, this goes without saying, but each individual is affected by the testing differently.   And while thousands of know-it-all Slowtwitch users can pontificate on the best helmet on the market or the ideal position, your specific characteristics drive your needs.  I can’t stress that enough as I go through my own individual results – the information makes sense for me, but may not even be remotely similar for many others.

The “aero” (and I use that term loosely) helmet I had been using was the Rudy Syton.  However, it had a large crack in it so I opted to bring my road helmet to test as my baseline.  As they informed me, each test would be about 40 or so seconds in duration and it would feel like a high tempo to threshold effort. They wanted to mimic a race like ride so that they could get as accurate position as possible (in a short amount of time).  We did this test twice to get a solid base:



Baseline Test. Game Face On. Obviously.


First and foremost, the wind speed was tested consistently at 30 mph.  Second, as you can see from the data above, there are numerous metrics that were measured.  Many people understand CdA and drag grams.  For this article, I am going to focus on “Aero Watts” as it is easiest to conceptualize.  With that in mind, focus on the “input MPH = 23” on the upper right corner of the table.  You’ll see that my MPH is set at 23, which is approximately my average speed in most of my 70.3 efforts.  Simply put, the “Aero Watts” is a measure of the power that is necessary to produce 23 mph on a flat course.  With the baseline, I was looking at 186-188.  There was definitely room for improvement.

Remember that dork-a-palooza from earlier?  Well, within that nerdfest, I definitely came across a recurring theme: an aero helmet saves watts/time.  Sure, the number itself changed from source to source and website to website, but that fact remained.  My next two tests were the Giro Selector and the Giro Advantage:

Feeling faster...
In case you need a clear interpretation, my road helmet is aero death.  I did not move one millimeter on my position, and still both aero helmets dramatically improved my position.  The Giro Selector (Test #2) is the newest addition of Giro’s aero line and an “upgrade” from the Advantage (Test #3).  The Selector was a little more difficult for me to get on quickly, and had significantly less ventilation.  While this contributed to the better aerodynamic numbers, it was the only helmet that made me sweat significantly during the short test.  The Advantage was a little cooler and did not have a built in visor, but it came in testing a bit worse (181 to 176).


...but not fast enough

There is one thing you may have already noticed: my general position isn’t that visually aero.  No one is going to take these pictures and put them on the cover of Triathlete Magazine or Peloton Magazine.  But, my preferred distance is long-course and positional comfort is as important as my general aerodynamic position.  If I am up and out of my aero bars for half of the race, what good would an aero position be anyway?  I happen to be a pretty flexible person, but based on some specific fit criteria (which is another post for another time) and my power numbers, this relative fit works.  Having said that, you can probably surmise that a long-tailed aero helmet won’t be the most ideal.  My back isn’t as flat as, say, Fabian Cancellara.  It was difficult for me to position my head to keep the tail of the helmet flush on my back – or at least close to that position.


So Aero

Not everyone can be like Fabian




















While Cancellara displays a great position for a long-tailed helmet, you can easily understand that I do not. It is difficult to see from the side view, due to the white back of the jersey, but if you look closely at the overhead shot of the Selector you can tell that there is a decent gap between my back and the tail.

Luckily for me, the A2 tunnel actually received some helmets from Kask to test just before my appointment.  One of these helmets was the Bambino, made famous during last year’s Tour de France by Team Sky and eventual winner Bradley Wiggins.  With its unique design and short tail, it became the next tested helmet.

Now we're talking

Did someone say free speed?  Yes. I. Did.  One helmet alone changed my aero watts from a 188-186 baseline to 173.  No positional changes. No additional physical effort.  One helmet.  That looks like a jelly bean.  To say that I was mildly excited is to say that McKayla Maroney was indifferent. FREE SPEED.
8 months later; still not impressed









If I didn’t make it clear enough that this test is individual in nature, I’ll give you a prime example: there was a gentleman who tested before me.  He tested a Cervelo P5, was very thin, and had an extremely aggressive position – it was almost cartoonish.  Even though the Bambino was almost 20 watts more favorable to me, it was EQUALLY as bad for him across the same 30 mph wind speed.  I’ll repeat: the same helmet that provided me free speed managed to strip it away from my predecessor.  Amazing.  With his aggressive position and body type, he was better equipped to utilize a long-tailed helmet.  On the other hand, the short tail – really, no tail – of the Bambino was able to better displace the wind across my back and more broad shoulders.  As I type now, I am still floored that there was a 40+ watt difference against 30 mph wind between he and I with the same helmet.

After determining that the Bambino was a potential winner, we set about making some tweaks and changes to my position.  Many of these changes took place within the cockpit area, mainly adjusting my stack height and/or aero bar angle/length.  Again, through this test another misconception I had was displaced: I had thought if I dropped my stack height even lower, I should be significantly more aero.  However, as you see in the table below, my results were relatively inconclusive, or at least, not indicative of a big change from my original position.  In addition, some of the positions below were not ones that I felt comfortable maintaining for 112 miles.


Still missing something
The picture to the left shows a slightly better back angle with lower stack height, and yet – and much to my surprise – there wasn’t much difference at all.  Now, I will admit that I need to do a better job of working on head position and that also can help reduce drag.  But as you’ll see in a moment, even with “head position awareness” there gain wouldn’t be significant with a smaller stem.

We conducted another test with the Selector to see if anything changed (it didn’t).  We then raised the stack height back, kept other changes (aero bar extension and pad width), and tested two more times with the Bambino, the final test focusing on “head position awareness”.


Winner. The last one is the fast one.  By practicing my “turtle head”, I was able to improve 4 aero watts off my previous best test.  We discussed the test results and realized that my best position was here because I was most comfortable.  Even had we reduced the stack height and I focused on my head position, my natural comfort is in the position you see to the left; hence, the best test result.

Free speed was mine!  I dropped 18 aero watts from my worst run to my best – with an aero helmet and a few small tweaks.  Crazy right?  Most importantly, I now had confidence with data back-up to know that I was in the best position possible to get the most out of my physical ability – nothing wasted.  Free Speed.

Free speed isn’t exclusive to me, you just have to read Haycraft’s blog, understand that aerodynamics are specific to the individual, and, you know, marry a significant other who “gets” your crazy hobby and gives awesome gifts.

3 comments:

  1. Tim,

    I thought I might introduce myself. I am the "gentleman" on the P5 who was in the tunnel before you on March 7th: the one with the "extremely agressive," "almost cartoonish" position. I am an older time trialist and that "cartoonish" position enables me to ride a 40K TT in a bit over 52 minutes at 57 years of age. Hopefully it will put me under 52 minutes this summer and give me a shot at the North American amateur 55-59 age group record for a 40K TT.

    So how did you find out about my position and my numbers, since I was already out of the tunnel when you arrived?

    Best wishes with your racing! It is clear you are a stud and your improved aerodynamics will make you even faster.

    Tail winds,

    El Colyer

    USA Cycling Licensed Level 2 Coach
    USA Cycling Certified Power-Based Training Coach

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  2. The only #s gotten were how different the Kask was on your head than on Tim's. It's a relative difference and is not absolute. Therefore the #s themselves have no real tangible value to anyone who might be scoping out the competition. JeffP posted your relative watts on the forums.

    This statement: "at 23mph the cartoonish fellow would require 125 aero watts" is more telling than knowing the differences b/w helmets.

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    Replies
    1. James,

      ThanksT So where are the forums where Tim posted this information? I am totally not concerned about anyone "scoping out the competition." I am very interested is hearing more about that "cartoonish fellow"!! :-)

      Tail winds,

      El

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