Tunnel Test Results
Test recipe: There is no such thing as a perfect wind tunnel test. The rider impacts the aero drag created by the bike, but replicating that influence is fraught with error and inaccuracy. A person shimmying or looking at a different point can skew the results. Some tri bike companies decide to test their designs with a dummy mounted to the bike. While this strategy does a great job at re-creating the interaction between rider and machine, a small difference in the dummy’s position can outweigh any disparity in the bikes themselves.
For Inside Triathlon’s test, we took elements of the best test procedures in the business and created one that can measure the differences between the bikes—although imperfectly—while keeping other variables to a minimum. Here’s how the bikes were tested at the Faster wind tunnel in Scottsdale, Ariz.
Bike setup conditions:
• All bikes were tested with the same Zipp Super-9 Clincher Disc and Zipp 404 Carbon Clincher front wheel.
• Bikes were tested without a rider or dummy.
• Saddle was removed from the bike and the seat post was set at a uniform height. Openings for saddle attachment hardware were covered with electrical tape.
• Elbow pad height was set equally for all bikes.
• Reach distance to the pads and bar tips was set equally for all bikes.
• Chain was positioned in the big chainring and smallest cassette cog.
• Shift levers were set horizontally.
• Crank arms were fixed in the horizontal position using a Velcro strap.
• The bikes were tested with the spec’d components and aerobars—translating this into a complete bike test, not a frameset comparison.
• No accessories were mounted on the bikes, including Specialized’s integrated Fuelselage hydration bladder.
• The bikes were tested in 30mph wind at 0, 5, 10, 15 and 20 degrees of yaw on both sides.
Test design drawbacks:
This test protocol isn’t perfect. These are the shortcomings that impact the test results but may not influence rider speed on the road.
• The lack of a rider is the most obvious shortcoming. The cyclist impacts the way air passes around the equipment, and this test neglects that fact.
• The tip of the seat post is exposed to unadulterated airflow in this test even though it is almost entirely hidden when the bike is actually ridden by a cyclist.
• Aerobar extensions are exposed to the wind when the rider’s hands would typically cover this portion of the bike.
To watch a video about the test and read more analysis, go to Insidetriathlon.com/tunneltest.
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