Back in February I was in the heart of NASCAR country at the A2 Wind Tunnel in Moorseville, North Carolina, just outside of Charlotte. This wasn't my first trip to a wind tunnel. I had gone through this many times before with athletes I have coached. This time was different, however--I was the rider. I had just gotten a Blue Triad SL and the company provides a free wind tunnel test to streamline the fit. This was going to be fun, a cakewalk, since I knew all about being aero--or so I thought. But I discovered a few things I had not expected. It's a lot different on the bike rather than on the sidelines. Here's what I learned.
If only I didn't have a head
Before we started I asked Mike Giraud, the bicycle aerodynamics specialist at A2, to name the most common correction he makes to riders' positions to get them more aerodynamic. "Lowering the head," he told me. And I agreed. That was exactly what I had found in helping to set bike positions. I knew that would not be my issue. Guess what? I was wrong. Even though I tried to get my head low, it still stuck up like a spoiler on Dale Earnhardt Jr.'s Chevy. We spent 90 minutes trying to get it down.
It isn't a La-Z-Boy
Keeping my head low was no easy task and certainly wasn't comfortable. There's a necessary balance between aero and comfort--you can't have both. We were trying to get me as aero as possible since most of my time trials are in the 20K range. For a half-hour you can afford to give up some comfort to shave a few seconds. An aggressively aero position would pay off. We pressed ahead trying to get my head to stay down.
It's Easier to Be Short Than Narrow
Mike had some success in lowering my head by bringing my aerobars down about 4 cm. I continued straining to get into what I had told my clients was the "turtleneck" position. My drag numbers got better. Then we started working on my front-end width by pulling my shoulders up toward my ears. While it seems to work for some riders, I didn't have much success there. The drag coefficient didn't improve.
You Don't Have to Do it Forever
After listening to me bellyache following 45 minutes of trying to stay low and narrow, Mike made a good point, which will now go into the list of things I tell my clients. "You only have to get small for a few seconds at a time," he said. Good point. You want to be the most aero when the affective wind speed is the greatest, such as when going downhill, or into a wind gust. So crunch into the smallest position you can for these situations. Otherwise, simply stay comfortably aero and concentrate on power production.
You Go Slow When You Get too Low
At one point my front end was down about 5 cm and my elbows were 6 cm narrower from my prior position. The drag decreased a little but the power dropped off quite a bit. My thighs were now bumping my stomach and the tight elbows forced my head up higher. The lesson there was that you can try to get too small. This will cost you power. Fast time trialing results from an optimal marriage of aerodynamics and power. If power drops 5 percent but you gain 5 percent in drag reduction, you're essentially going just as fast at a lower effort. And if you get on the TT bike once a week for an interval session you can probably boost the power once adapted to the new position and go even faster.
So what did my numbers say after 90 minutes in the tunnel? When I started my coefficient of drag was 0.761. In my optimal position it was 0.704. That amounts to about 44 seconds in a 20K time trial. Could I have accomplished that by forgoing the wind tunnel and simply training more? Perhaps. But I suspect not. That's a ton of intervals and suffering. It's a lot easier to keep my head down for a half hour.