Review: BMW 2013 M6 Convertible

BMW fanboys ritually enrapture themselves over the small blue, purple, and red "M" badge that designates the brand's hulkier strains.

But these are divisive times for the Bayerische Motoren Werkes' in-house performance shop. The 7,104 "M" cars which made their way into US driveways last year are but a sliver of the nearly quarter-million vehicles sold annually by the German manufacturer, yet the boutique sub-brand is the sacred cow that can lead the faithful to believe, or revolt and insist BMW has gone Buick with squishy steering feel and soft suspension.

The M6 is all grown up, with a big, sophisticated drivetrain, copious bells and whistles, all the pesky baggage that comes with middle age.The lunatic fringe obsessed with horsepower-inspired horseplay stalks new model specifications with fervor, and the House of M has offered no shortage of variance over the years. For instance, only the first two successive M5 models possessed the same engine layout, a naturally aspirated inline-6. Since then, a V8 ruled the roost until the V10 came along, an F1-inspired screamer that was both hard on the ears and the fuel tank. Following that, the Munich-based cult proclaimeth the future would be turbocharged, despite earlier promises against M cars with forced induction.

Thus, the latest M6 and its ragtop variant pack the same powerhouse as the M5 sedan, a 4.4-liter V8 with twin-turbos nestled cozily between the cylinder banks for tidier packaging and quicker response. This techy, direct-injected engine pumps 560 horsepower and 500 pound-feet of torque – which commences at a leisurely 1,500 rpm and doesn't quit until the tach approaches 6,000 rpm, just 1,200 rpm shy of redline.

Performance parameters can be manipulated with Choose Your Own Adventure levels of options: A smattering of buttons around the shifter command everything from steering effort to throttle response, transmission shift patterns, stability control intrusiveness, and suspension damping. Buttons on the steering wheel can be programmed with your favorite shortcuts to dynamic bliss, though it takes some fiddling to optimize the mélange of motoring variables, which I discovered during an afternoon with the M6 Convertible on the highways and byways outside California's sleepy bedroom community of Santa Barbara.

The cockpit is welcoming enough, with firmish but friendly seats that, like the drivetrain settings, don't lack for adjustability. Sensing a trend here? Yep, aspects of this car are aimed at your nephew, not you, despite the restrained instrumentation (typical BMW) and the cinematic, landscape-oriented nav screen that, as also seen in the new 3-series, sadly doesn't disappear beneath the dash.

Unlike the M5's artificially enhanced acoustics (which route a simulacra of engine sounds through the speakers), the M6 goes au natural with an exhaust note that's purely gaseous – and surprisingly hushed. The canvas top incorporates a carbon fiber reinforced plastic structure for strength and weight savings, and when it's up, the M6's engine sounds like a retiring lilly of a mill, with barely audible whooshes and low frequency hums that belie the torquey acceleration on tap. Humming along the inside of a tunnel, lowered windows and two taps of the downshift paddles reveal restrained sounds coming from behind; not until you're driving top-down do the engine notes become incrementally more tasty (but never overstated), with a finely modulated hum suggesting the twin-power V8 is just getting started, even as it compresses you into your Merino leather seats with mean, pushy pressure. Even in more aggro settings, the dual-clutch 7-speed transmission shifts swiftly and smoothly during most acceleration runs. With launch control initiated, the M6 ragtop can gallop to 60 mph in 4.3 seconds. Brakes are also appropriately effective, as repeated left pedal jabs along Ojai's legendary Highway 33 produced reassuringly strong stops.

But speaking of weight, the very heft that seemed to disappear in a straight line nudges back into perception when the road bends. It's not that the M6 doesn't handle itself intuitively – it does, thanks to a rear axle whose subframes are rigid-mounted to the body. But with the optional 20-inch light alloy wheels wrapped in 265mm front and 295mm rear rubber, the M6 ragtop carries 4,508 pounds of mass to hustle along in either direction, and that poundage detracts from the loving attention paid to the punchy yet silky V8, the sublimely buttery but expedient gearbox, and the impressive compromises made between ride quality and road feel. Sure, there are hints at lag from low rpms before an exhilarating rush of torque that carries strongly through the powerband, but the engine's robustness never makes you pine for its predecessor, which supplied 10 percent less horsepower and 30 percent less torque.

In a spider graph of driving pleasure, there's more satisfaction to be had in the act of accelerating an M6 Convertible than in turning, due to the inevitable physical challenges of altering the course of a 2.1-ton vehicle. And don't assume switching the steering to Sport+ solves the problem; that most aggressive setting creates a too-heavy feel that makes flicking the car through corners more challenging than it ought to be. Best to stay in Sport mode, though even then, BMW's Servotronic setup will likely disappoint purists with its tendency to quicken the steering ratio at lower speeds, a disconcerting dynamic when you're carving corners.

There's no shortage of power, speed, and handling stability on tap with the M6 Convertible.There's no shortage of power, speed, and handling stability on tap with the M6 Convertible – witness the fact that no fewer than five journalists on the car's press introduction took home special mementos from the California Highway Patrol, one of which commemorated the achievement of hitting 136 mph in a 55 mph zone. But there's also something missing for anyone who's ever driven the first mass-produced M car, the E30-series M3, a lightweight, tossable little animal with an endearing appetite for apexes. The M6 is all grown up, with a big, sophisticated drivetrain, copious bells and whistles, all the pesky baggage that comes with middle age.

In an unlikely twist of fate, the famously fuddy-duddy folks over at Mercedes-Benz have taken a turn for the sportier, re-working their new SL63 AMG roadster with an aluminum chassis that trims serious weight and makes it feel more glued-in than ever before. It may lack some of the steering cues and intuitiveness of the M6, but the Benz's progress toward performance should be disheartening to BMW engineers, who have managed to allow each generation of M6 to accumulate more weight than its predecessor. The only things working against the Benz? Its brutal $146,695 starting price, a behind-the-times transmission that lacks the sharp reflexes of the BMW's seven-speed, and a seemingly intentional detachment from driver involvement.

Despite its undeniable straight-line punch and deeply developed technological bits, the BMW M6 Convertible offers more to appease the country club set than it does the cognoscenti. Not that there's anything inherently wrong with a lifestyle-oriented high performance car, but committed enthusiasts simply won't be able to drown out their discontentment with the discreetly subtle exhaust note no matter how much they lower the windows and rev the engine.

There's only one cure for the disease: the automotive equivalent of gastric bypass surgery. Until it takes those strides – which BMW execs promise is coming in future models – the M6 is bound to appeal to a broad but spendy spectrum of the population that doesn't mind pirouetting with a zaftig yet zippy dancer.

WIRED Quiet and smooth enough for epic road trips. $32,700 price savings over SL63 AMG leaves lots of leftover dough for hair transplant fund. Dual-clutch gearbox makes all but the biggest Luddites stop wishing for a clutch pedal.

TIRED Muted muffler makes you pine for more acoustic audaciousness. Middle-aged paunch calls for a juice cleanse. Where'd the M's punky roots go?

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