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Cd Value

Cd Value

The Cd value is the drag coefficient. It is measured in the wind tunnel and sums up the vehicle’s aerodynamic qualities.

This comparative quantity describes the "formal quality" of bodies, irrespective of their size. A number of factors influence the Cd value, including the vehicle shape (saloon, estate or hatchback). Narrow gaps and joints reduce buffeting and keep drag low. The design of the underbody also has an effect on the Cd value.

The lower this value, the more aerodynamically efficient the vehicle’s design. A precise statement regarding the vehicle’s aerodynamics can only be made once both the Cd value and the vehicle’s frontal area (the projection of the vehicle’s front outline onto a plane surface) are known. A small vehicle may have a higher Cd value than a large saloon, but its aerodynamic drag could still be lower due to the smaller frontal area.