per degree on the roadster), which improves turn-in and overall handling response. The roof has a "double-bubble" contour which serves as an aerodynamic aid and offers more headroom than the roadster with the soft top closed. The Coupé has a sleek fastback rear window that slopes down to an integrated spoiler which is shaped to deliver downforce to the rear axle at high-speed. The model range for the Coupé was more limited than the roadster, and consisted of the six-cylinder 3.0si and Z4 M model only. Transmission choices were a 6-speed manual and a 6-speed automatic with shift paddles mounted on the steering column. Chassis and body Compared with its Z3 predecessor, the Z4 is larger and has a stiffer chassis. As per the Z3, the front suspension is a Macpherson strut design. The rear suspension uses a multi-link design, instead of the semi-trailing design used by the Z3. The Z4 used lightweight materials to offset the increased weight over the smaller Z3, such as an aluminum hood and suspension components, magnesium roof frame. Run-flat tires removed the need for a spare tire, which reduces weight and allows for a larger trunk. Equipment The 6-cylinder engines included all-alloy construction, variable valve timing (double-VANOS), and throttle by wire. Safety technology included four-wheel disc brakes and electronic stability control, incorporating ABS and traction control. An optional "Sport Package" included added stiffer and lower suspension, 18 inch wheels, and sport tuned electronic steering, throttle and shift parameters ("Dynamic Driving Control"). Electric power steering replaced the traditional hydraulic power steering used by the Z3. The power assist is speed-sensitive, allowing for easier maneuvering at low speeds. However, the Z4 M uses hydraulic power steering, and has been judged as having a more direct and communicative feel to the steering. In 2002 a 6-speed SMG gearbox was offered as an option on the 2.5 and 3.0 roadsters. Transmissions The available transmissions were: 5-speed manual Getrag S5D250G (2.2i, 2.5i) 6-speed manual Getrag GS6-17BG (2.0i, 3.0i) 6-speed manual ZF GS6-37BZ-TJEE (Z4M) 6-speed manual ZF GS6-37BZ-TJES (3.0si) 5-speed automatic ZF 5HP19 (2.2i, 2.5i, 3.0i) 6-speed automatic ZF 6HP19 (3.0si) 6-speed GS6-S37BZ SMG automated manual (2.5i, 3.0i) Models * The 2.0i was only sold in Europe. All models are E85 roadsters except as noted. European specifications shown. North American vehicles may have slightly lower power ratings. US models include 2.5i Roadster, 3.0i Roadster, 3.0si Roadster & Coupé, M Roadster