The hatchback's shape helps the Z slice through the air with a minimum of drag (0.29 on the Track model). The Roadster's more traditional coupe outline isn't quite as slippery, attaining a drag coefficient of 0.34. (But what do you care when you've got the wind in your hair?) Underbody airflow is managed well, with zero lift on the front (and zero lift on the rear of the Track model). All this math adds up to relatively low levels of wind noise, even in the Roadster with the top up, and a stable sports car at high speeds.
With the top down, conversation in the Roadster required only slightly raised voice levels; the stereo did, however, have to be cranked up a bit. Next Page