MUNICH, GERMANY – BMW will unveil its first roadster with a retractable hardtop, the all-new 2009 Z4, at the North American International Auto Show in Detroit in January, according to Auto Week.

The first complete makeover of the Z4 since its debut in 2002 features a two-piece aluminum top that can open or close in 20 seconds. It collapses into a back compartment that BMW says allows the car to maintain its traditional low-slung design and proportions. No soft-top version will be offered.

The top model, the sDrive35i, gets a twin-turbo, direct-injection 3.0L inline-six that achieves 300 hp and 300 lb.-ft. of torque. The sDrive30i gets a normally aspirated 3.0L straight-six rated at 255 hp and 220 lb.-ft. of torque.

Both versions come standard with six-speed manual gearboxes. The sDrive35i offers a seven-speed dual-clutch automatic as an option, while the sDrive30i has an available six-speed automatic. BMW says the swiftest combo, the twin-turbo with the seven-speed automatic, can hit 0-60 mph in 5 seconds.

Like its predecessors, dating back the original Z3 that first appeared in 1995, the new Z4’s exterior is marked by an extended hood, large wheel arches, and a long wheelbase and small overhands. The rear-drive cars have a nearly 50-50 weight distribution. A lightweight aluminum suspension can be upgraded with an optional sport pack that adds an adaptive suspension with electronic damping control. Seventeen-inch wheels are standard.

The Z4 is the first BMW roadster to get iDrive as part of the optional navigation system. Unlike the previous Z4 that was built in Spartanburg, S.C., the new Z4 will be assembled alongside the 3-series folding hardtop convertible in Regensburg, Germany.

The 2009 Z4 goes on sale in May in the U.S., priced in the low $50,000s for the sDrive35i and in the mid $40,000s for the sDrive30i.