Aerodynamics and You

My husband loves racing triathlon. I prefer road bike racing. I make fun of him for his tricked-out time trial (TT) bike and his “space ship helmet.” He mocks me for “needing” to draft in order to win a race. So yeah, we both ride, but our bikes look drastically different, and our cycling sports of choice have unique methods of overcoming wind resistance. In road bike racing, I draft off my teammates (hence the term “wheel sucker”). In triathlon (or TT racing), Ryan rides solo and it’s his equipment that reduces drag (hence the term “tri geek” or, my favorite, “triassolet”).

Equipment that reduces drag. That’s a claim with the potential to feed a lot of marketing scams. What really makes a difference in speed when it comes to bike gear? Does a tri geek’s bike really make him faster?

According to HED Cycling Products, an aerobar and wheel manufacturer in Minnesota, speed on the bike is determined by two factors. The first is how much power you are able to produce, measured in watts. The second is wind resistance (or drag), which is usually measured in pounds through wind tunnel testing.

At 25 miles per hour on flats, 80 percent of an average rider's power output is used to overcome the effects of drag. That’s a big number. It means that reducing wind resistance via a tricked-out TT bike is going to make you faster than you would be on a regular bike, even with greater power output.

Alright, the aerodynamics argument makes sense. Say I was convinced; how much faster are we talking? Seconds? Minutes?

A study done in 2007 by Kim B. Blair, Ph.D, for Sports Innovation Group LLC, provided the most compelling data I’ve found to date. He used wind tunnel testing to determine which aero components resulted in the greatest improvement in speed. His subject was a 160-pound male cyclist with “good” aero position riding the equivalent of a 40-kilometer time trial.

Blair studied six variables:

Details like cable routing
Aero frame versus round tube frame
Dialed-in aero position versus good position
Aero helmet versus road helmet
Aero wheels (disk) versus standard
Aero waterbottle versus regular bottle on frame

The biggest speed increase, 150 seconds over 40 kilometers, came from using a dialed-in aero position. This means that no matter what kind of bike or accessories you have, the best thing you can do is get a bike fit. The next one surprised me: using an aero waterbottle, for an increase of 110 seconds. That’s a small investment compared to say, a new frame. Dr. Blair explained that the aero waterbottle used in his testing was a unique prototype created by a student he was supervising at MIT, and not akin to the aero waterbottles available on the market today. He had no data to either confirm or deny the validity of currently available aero waterbottles. Bummer. But hey Dr. Blair, a business opportunity is knocking!

Next came the aero helmet, for an increase of 90 seconds. I would have guessed the wheels, but changing out the wheels made as little difference as adjusting details like cable routing, both saving about 45 seconds each. What’s interesting is that aero wheels, because they are rotating weight, have typically been considered to offer the greatest time improvement, even more than the frame itself.

And speaking of the frame, Blair’s experiment showed a speed increase of about 50 seconds by using an aero frame. I was pretty floored that the most expensive adjustments – an aero frame and disk wheels – did not offer the greatest pick-up in time. While I wouldn’t go so far to call it a marketing scam, a misperception certainly exists among consumers as to where to get the most bang for your buck. According to Dr. Blair’s study, your best bet is a bike fit and a new helmet, the combined cost totaling about a fourth of the amount of a new frame or new wheels.

Seems to me like I’ve got a new thing to tease Ryan about – I could outfit my road bike with a pair of aerobars, get a bike fit to dial-in my new position, purchase a space ship helmet, and keep pace with him just fine. And for a lot less money than he spent on Bellatrix (yes, that’s the name of his TT bike). And I’ll throw in an aero waterbottle, just in case.