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From the pages of Velo: VeloLab’s Aero Revisited

Torsional Stiffness Results

The torsional stiffness test we co-developed with Microbac Laboratories, Inc. measures how a bike moves at three different points while subjected to a simulated pedaling force. Here’s how it works.

The front fork is fixed. The rear dropouts are mounted to a dummy axle that pivots on an eyebolt, allowing the rear of the bicycle to twist and move laterally. A chain is connected from the large chainring to the dummy rear axle to transfer the pedaling force through the rear triangle.

Dial indicators contact the bike at the center of the drive-side crankarm’s face, at the top of the head tube and at the top of the seat tube. Two 50-pound dumbbell weights are hung on a spindle screwed into the left crank positioned horizontally forward and the values are recorded on the three dial indicators.

Wind Tunnel Results

For these illustrations, we compared the four test bikes with ENVE Smart 6.7 wheels to a standard road bike with the same wheels. We calculated a weighted average for drag in the wind tunnel across all yaw angles to produce an overall representation of each bike.

Time Saved Over 40km

Power to overcome aerodynamic drag is drag force times velocity, but the equation is not linear, because as the drag force decreases, the speed increases, which then causes an increase in the drag force, etc. As long as the changes are small, relative to the total drag force of the bike and rider, however, we can use a simple linear relationship: that 50g of drag force = 5w power savings = .5s/km at 30mph.

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