Free Speed – Lessons from the Wind Tunnel (Bikeradar)

By Ben Day

We all want to be faster. In order to go faster, you have four choices – increase your power, reduce your weight (therefore improving your watts per kilogram), or improve your positioning and aerodynamics on the bike or lastly, buy fast (and usually expensive) equipment.

Anyone already training with a well-designed training plan is investing in the power increase, which hopefully will coincide with a reduction in body mass, so what’s next? Aerodynamics!

In the past decade, top bike, wheel, component, clothing and helmet manufacturers have been investing heavily into research and development of their products, and the wind tunnel is where they optimize these products for speed, or, more technically speaking, a reduction in drag. Non-disclosure agreements abound, meaning technicians of wind tunnels across the world are privy to lots of cool secret information!

I have observed an already fast athlete save a further 16 watts by the end of a session in the wind tunnel. This may not sound like a lot but think for a moment how hard and how long you have to train, or quite how much you would have to spend on equipment in order to gain 16 watts at your lactate threshold.

The FASTER Performance Center, a boutique bike shop/recovery center/wind tunnel combo, located in Arizona, relies upon Aaron Ross as the director of technology and biomechanics (he’s a bike fitting and wind tunnel technician guru). Combining his knowledge with ‘shred’ after shred of wind tunnel runs has given Ross the experience to understand how the invisible wind reacts to different shapes. What can we learn from his knowledge? Let me take you inside!

Everyone is different

It is difficult to make a general assumption as to what is fast for a person without taking into account their mobility. That is why a bike fit is a necessary component of optimizing speed, not only in the wind tunnel but also out on the road.

Just because some are faster with a lower position, don’t assume you will be

“One of the worst things to assume is getting a rider lower will automatically make them faster. By dropping the front end you may lower some aero drag, but you may lose a lot of pedalling efficiency, and may not be able to hold it throughout an event.”

“Getting a rider to sit low in the bike is paramount, but that does not necessarily mean a low front end. Understanding what their range of mobility is like allows us to best see what their aero drag numbers are while still pedalling efficiently.”

Aaron Ross

Working at it to get fast

You can spend all the money you want, but when it comes time to race, it’s the rider on top that counts

Fast equipment is just a small part of the story. Optimizing your speed is partly up to you as well. Ross believes that the posture that the rider needs to remember to hold is 60-70 percent of the speed equation. But without a quality bike fit acting underneath that as a stable foundation, the position will be inefficient.

“You can have the most aero bike or equipment in the world, but if your ideal body position is not going to match with the bike or the equipment, then there will be compromises somewhere,” Ross says.

Revolution or evolution

Aerodynamic improvements can be a revolution, with the initial session being very valuable, but they become evolutionary as a rider further adapts to their position, creating comfort and efficiency aerodynamically. Ross says he often sees that after this initial period of time further refinements can be undertaken and employed to find a new level.

Wind Tunnel vs. Reality

Ross has seen that there is a direct correlation between wind tunnel data and the real world – the reason why the top bicycle and equipment companies invest in tunnel time. “The wind tunnel testing is done in a controlled environment as this makes it easier to see small differences,” he says. “We also have the rider pedal under load, which will help simulate outside riding conditions. As we go through the athlete’s tunnel protocol, and we check for repeatability, we can really understand what the rider can realistically do outside.”

If you’re serious about going fast against the clock, time in a wind tunnel may be money well spent. At FASTER, investment in wind tunnel time is summed up in an interesting way: grams of drag (a measure of the air resistance) reduction divided by dollars spent. An aero bike saves 1g for roughly every US$22.50 spent.  Wheels, US$18 for every gram saved. You on your bike, in the wind tunnel in an optimized position, equals roughly $1 for every gram of drag saved.

The ‘do it yourself’ method

If you don’t have access to a wind tunnel and you still want to improve on your aerodynamic position, you can do so with the help of your power meter. One simple method, although not as accurate as a wind tunnel, is to find a venue with limited variables such as a windless stretch of road where you can test in both directions.

Complete one pass in both directions at a constant speed (remove the acceleration and deceleration at both ends of the run) over a known distance (at least 500m) and record average power for the runs. Quickly make changes to your position to reduce the effect of changing weather conditions on your testing, and complete another pass in both directions at the same average speed. Compare average power over the runs to determine how much you saved.

Special thanks to Aaron Ross at the FASTER Performance Center for his insight and experience.

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