D2

Aerodynamic performance is affected by wind direction. To create the D2 rim, SHIMANO engineers considered both frontal and cross winds, aiming to achieve optimal performance in real-world riding conditions. Extensive prototype testing, in the wind-tunnel and on the road, proved that a wide rim shape with a deep tire bed performs best across a wide range of conditions. At yaw angles ranging from 0 to 15 degrees, the SHIMANO D2 rim profile reduces air drag better than others aero shape rims. This rim design also boosts lateral wheel stiffness and offers improved vertical compliance for increased control, comfort and durability on the road.

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Aerodynamics

Compared to the conventional product C40-TL, air resistance has been reduced at all yaw angles on C36-TL, which has about the same rim height. In the conversion method that considers the direction of the winds received under actual running conditions*, the drag has been reduced by about 3 W.
Of course, air resistance has been further reduced on both C50-TL and C60-HR-TL.

* Calculated by weighted averaging the air resistance values measured in wind tunnel tests with the wind direction ratio of the winds received during running. The wind direction ratio is obtained by actually measuring, with an ultrasonic anemometer, the direction of the winds received by a rider when traveling at a speed of around 48 km/h in an environment with a wind velocity of 3 to 5 m/s.

[Measurement conditions (Graph for wind tunnel tests)]
Value of air resistance generated at the front wheel alone
Wind velocity/wheel rotation speed: 48 km/h
Tire: Schwalbe Pro One TLE 25c