The BMW 6 Series Convertible (F12) 640i Steptronic, produced from 2011 to 2015, represented a sophisticated blend of performance and luxury within BMW’s premium convertible lineup. Positioned as a mid-range offering within the F12 generation, it slotted between the entry-level 630i (where offered) and the high-performance 650i. This variant aimed to provide a balance of spirited driving and comfortable cruising, appealing to buyers who desired a powerful yet refined open-top experience. The F12 6 Series, as a whole, aimed to recapture the grand touring spirit of its predecessors, offering a more driver-focused experience than some of its competitors.
Technical Specifications
| Brand | BMW |
| Model | 6 Series |
| Generation | 6 Series Convertible (F12) |
| Type (Engine) | 640i (320 Hp) Steptronic |
| Start of production | 2011 |
| End of production | 2015 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (economy) – urban | 10.9 l/100 km (21.6 US mpg, 25.9 UK mpg, 9.2 km/l) |
| Fuel consumption (economy) – extra urban | 6.2 l/100 km (37.9 US mpg, 45.6 UK mpg, 16.1 km/l) |
| Fuel consumption (economy) – combined | 7.9 l/100 km (29.8 US mpg, 35.8 UK mpg, 12.7 km/l) |
| CO2 emissions | 185 g/km |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 5.7 sec |
| Acceleration 0 – 62 mph | 5.7 sec |
| Acceleration 0 – 60 mph | 5.4 sec |
| Maximum speed | 250 km/h (155.34 mph) |
| Emission standard | Euro 5 |
| Weight-to-power ratio | 5.8 kg/Hp, 173.9 Hp/tonne |
| Weight-to-torque ratio | 4.1 kg/Nm, 244.6 Nm/tonne |
| Power | 320 Hp @ 5800-6000 rpm |
| Power per litre | 107.4 Hp/l |
| Torque | 450 Nm @ 1300-4500 rpm (331.9 lb.-ft. @ 1300-4500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | N55B30A |
| Engine displacement | 2979 cm3 (181.79 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 84 mm (3.31 in.) |
| Piston Stroke | 89.6 mm (3.53 in.) |
| Compression ratio | 10.2:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Direct injection |
| Engine aspiration | Twin-power turbo, Intercooler |
| Engine oil capacity | 6.5 l (6.87 US qt | 5.72 UK qt) |
| Coolant | 9.3 l (9.83 US qt | 8.18 UK qt) |
| Kerb Weight | 1840 kg (4056.51 lbs.) |
| Max. weight | 2290 kg (5048.59 lbs.) |
| Max load | 450 kg (992.08 lbs.) |
| Trunk (boot) space – minimum | 300 l (10.59 cu. ft.) |
| Trunk (boot) space – maximum | 350 l (12.36 cu. ft.) |
| Fuel tank capacity | 70 l (18.49 US gal | 15.4 UK gal) |
| Length | 4894 mm (192.68 in.) |
| Width | 1894 mm (74.57 in.) |
| Height | 1365 mm (53.74 in.) |
| Wheelbase | 2855 mm (112.4 in.) |
| Front track | 1600 mm (62.99 in.) |
| Rear (Back) track | 1665 mm (65.55 in.) |
| Ride height (ground clearance) | 123 mm (4.84 in.) |
| Drag coefficient (Cd) | 0.31 |
| Minimum turning circle (turning diameter) | 11.7 m (38.39 ft.) |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 8 gears, automatic transmission Steptronic |
| Front suspension | Double wishbone |
| Rear suspension | Independent multi-link suspension |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Electric Steering |
| Tires size | 225/55 R17 97Y |
| Wheel rims size | 8J x 17 |
INTRODUCTION
The BMW 640i Convertible (F12) debuted in 2011 as part of the redesigned 6 Series. This generation marked a return to a more sporting character compared to the previous E64 model, emphasizing driver engagement and a luxurious experience. The 640i, powered by the N55 engine and paired with the 8-speed Steptronic automatic transmission, was designed to appeal to buyers seeking a balance between performance and fuel efficiency. It occupied a crucial position in the lineup, offering a compelling alternative to the more expensive and powerful 650i, and providing a more refined experience than potential entry-level options.
Powertrain & Engine Architecture
At the heart of the 640i lies the N55B30A, a 3.0-liter inline-six cylinder engine. This engine is a significant evolution of BMW’s long-standing inline-six tradition, featuring direct fuel injection, a twin-scroll turbocharger, and variable valve timing (VANOS) and valve lift (Valvetronic) technologies. The N55 produces 320 horsepower at 5800-6000 rpm and 450 Nm (331.9 lb-ft) of torque between 1300 and 4500 rpm. This broad torque curve contributes to strong acceleration across a wide range of engine speeds. The engine’s layout is front-mounted and longitudinal, driving the rear wheels. The 8-speed Steptronic automatic transmission is a key component, offering smooth and quick shifts. It features a torque converter and allows for both fully automatic operation and manual gear selection via steering wheel-mounted paddles or the gear selector. The transmission’s gear ratios are optimized for both performance and fuel economy, with a relatively tall final drive ratio to enhance cruising efficiency.
Driving Characteristics
The 640i Steptronic delivers a refined and capable driving experience. While not as brutally fast as the 650i, the 320 hp engine provides ample power for spirited driving. Acceleration from 0-60 mph takes approximately 5.4 seconds. The Steptronic transmission contributes to smooth and seamless gear changes, enhancing the overall driving comfort. The engine’s torque delivery is particularly noteworthy, providing strong pull from low engine speeds, making it well-suited for everyday driving and overtaking maneuvers. Compared to a manual transmission-equipped 640i, the Steptronic version prioritizes ease of use and comfort over outright driver involvement. The automatic transmission’s programming is geared towards smooth shifts and efficient operation, rather than aggressive downshifts during cornering.
Equipment & Trim Levels
The 640i Convertible came standard with a comprehensive list of features, reflecting its positioning as a luxury vehicle. Standard equipment typically included leather upholstery, power-adjustable seats with memory function, a premium sound system, automatic climate control, and BMW’s iDrive infotainment system with a high-resolution display. Optional extras were plentiful, allowing buyers to personalize their vehicles. Popular options included upgraded leather trim, a head-up display, active steering, adaptive cruise control, and a Bang & Olufsen sound system. The convertible top was a fully automatic retractable hardtop, offering excellent insulation and security when raised. Interior trim options included various wood veneers and aluminum accents.
Chassis & Braking
The F12 6 Series Convertible features a sophisticated chassis designed to deliver a balance of comfort and handling. The front suspension utilizes a double wishbone design, while the rear suspension employs an independent multi-link setup. This configuration provides excellent wheel control and minimizes body roll during cornering. The 640i typically came equipped with ventilated disc brakes on all four wheels, providing ample stopping power. Anti-lock braking system (ABS) and electronic stability control (ESC) were standard safety features. The steering system is a rack-and-pinion setup with electric power assistance, offering precise and responsive steering feel.
Market Reception & Comparison
The 640i Convertible was generally well-received by automotive critics. It was praised for its refined driving experience, luxurious interior, and powerful engine. However, some reviewers noted that it lacked the outright excitement of the 650i. Compared to the 650i, the 640i offered a more affordable entry point into the 6 Series range, with lower running costs due to its smaller engine. Fuel economy was a strong point, with combined fuel consumption figures around 29.8 US mpg. Reliability was generally good, although some owners reported minor issues with the iDrive system and the convertible top mechanism.
Legacy
The BMW 640i Convertible (F12) remains a desirable used car today, offering a compelling combination of style, performance, and luxury. The N55 engine is known for its reliability and tunability, making it a popular choice among enthusiasts. While maintenance costs can be higher than those of more mainstream vehicles, the 640i provides a rewarding ownership experience for those who appreciate a well-engineered and refined grand tourer. The F12 generation 6 Series, including the 640i, helped to re-establish the 6 Series as a significant player in the luxury convertible market.
