Last available in 1989, BMW reintroduced the 6 Series to the U.S. market in coupe and convertible forms for 2004. Powered by a 325-horsepower, 4.4-liter Valvetronic V-8, the luxury sport two-doors are related to the company's 5 Series sedan.
The 645's lightweight construction makes ample use of aluminum and composite materials. BMW offers three six-speed transmissions, including BMW's Sequential Manual Gearbox, which has shift paddles on the steering wheel. Dynamic Driving Control is standard. At the touch of a button, the two-level system alters steering and allows the transmission to hold gears longer.
Active Roll Stabilization, BMW's Dynamic Stability Control stability system and 18-inch run-flat tires are standard. A head-up display is optional. Adaptive headlights swivel to illuminate curvy roads.
Active Steering, which varies the degree to which the front wheels turn in response to steering inputs, is available for 2005 either as a stand-alone option or as part of the Sport Package. Park Distance Control is standard, and Active Cruise Control is optional.
Exhibiting what BMW calls classic proportions, the coupe is long, low and wide and features a sculptured power dome hood. Set back on the chassis, the passenger compartment has a low roofline. A large, tilting panorama glass roof is standard in coupes.
An all-aluminum suspension minimizes unsprung weight. Convertibles have a vertical glass rear window that powers up and down and serves as a wind blocker when the top is down.
Up to four occupants can fit inside the 2+2 coupe and the convertible. Like BMW's 5 Series sedans, the 645Ci uses the iDrive system; a single knob on the console controls multiple comfort and convenience functions. Trunk space totals 13 cubic feet in the coupe, but less in the convertible. Sirius Satellite Radio and a Logic7 audio system are optional.
Under the Hood
BMW's 4.4-liter Valvetronic V-8 produces 325 hp and 330 pounds-feet of torque. Three six-speed transmissions are offered: manual, automatic with a manual-shift provision and BMW's Sequential Manual Gearbox, which incorporates a selector lever and shift paddles on the steering wheel.
BMW's Head Protection System in coupe models combines inflatable tubular elements with a stabilizing sail for increased protection. Side-impact airbags are standard. Convertibles are fitted with roll bars that deploy in an emergency.
Like most BMWs, the 645Ci is a serious driver's car. The suspensions are sufficiently taut, and occupants may experience a jittery sensation while rolling over certain surfaces. But this excess motion doesn't really translate to a harsh ride. In any case, it's a small price to pay for such superior control.
The seats are satisfyingly supportive, snugly bolstered and more comfortable than their firm cushions suggest. Visibility in the coupe is acceptable, but the mirrors could be larger and the B-pillars and tapered rear quarter glass impose some limits. BMW's iDrive system is technically innovative, yet it's sure to annoy some drivers.
Performance is impressively energetic with a regular manual gearbox, but the SMG unit is less alluring. In automatic mode, lower-gear upshifts are often sloppy and jerky. Paddle-shifting manually yields smoother results. Backseat space is nearly nonexistent when the front seats are moved back.