BMW M6 Convertible 2013 Review - International

BMW M6 Convertible

What we liked:
>> Lovely interior treatment
>> Destructive engine note
>> Surprising handling prowess

Not so much:
>> Laughable boot space
>> Old-school wind blocker
>> Steering wheel a bit fat

OVERVIEW
>> Too much mill?
It’s always a tough ask -- sticking high horsepower inside a convertible bodyshell, especially if the car in question wasn’t designed from the ground up as a soft-top.

BMW knows this better than most. The six-cylinder versions of its Z3 were poster children for body flex and poor handling; the M versions verged on diabolical. And the job gets harder again when the hole is so big that four people can enjoy the sunshine. The rule of thumb in engineering is that the bigger the hole, the sloppier the end result will be.

And the more power and torque you stuff into it, the more problems you’re going to have!

All that considered, the M6 Convertible had every excuse not to live up to the lofty ambitions M holds for its machinery.

It need not have worried. The successor to the V10-powered M6 Convertible, the new car combined enormous horsepower with a quality ride and a thumping engine note to be a real surprise packet.

For your starting price, itself not insignificant, you get M Sport seats with the belt integrated into the backrest (there are no B-pillars to host them). They are supportive and terrifically comfortable, with soft initial cushions that eventually demonstrate their long-drive strength with firmer cushions below. They’re fully electric too, with pneumatically adjustable lumbar support and active headrests which move to minimize whiplash if you get freckle punched.

Both front seats are heated and each side of the car has its own climate-control brain, so travelling temperature isn’t direct dependent.

Besides the M6 logos all over the place, it has cruise control, it has a fairly disappointing standard audio system and it has satnav with BMW’s now normal permanent stand-tall display atop the dash.

While there's little that isn't standard (check out our local drive of the 6 Series for more), still the optional equipment list is truly frightening. Radar cruise, head up display, ConnectedDrive… It goes on. And on…

MECHANICAL
>> Big power but how did they make it handle?
BMW could have done what it did last time and not endow the engine with enough low-end torque, nor endow the chassis with enough ability to resist the twist. They’ve worked hard on it this time, though, and resist it does.

The engine is a monstrous thing in an M5, and it’s even more monstrous in the M6, largely because lopping off the roof lets more of the intake and exhaust noise into the cabin.

It doesn’t have to be poked with a stick to make it want to fight, either. There’s 680Nm at 1500rpm and the torque delivery remains at that high peak until 250 revs shy of the power peak (6000rpm). By then, 412kW are trying to tear the flywheel off, with two twin-scroll turbos sitting in the 90-degree vee adding potency to every breath. It has 10 per cent more power than the old M6 Convertible, 30 per cent more torque and, as a bonus, it uses 30 per cent less fuel doing it.

This one is far more rigid, with extreme bracing in the engine bay and beneath the cabin floor, but while it’s made the car stiffer, it’s also made it enormously (and we mean enormously in the enormous sense) heavy.

It’s 1980kg with nothing in it, so it’s over two tonnes by the time you brim it with enough fuel to get it anywhere useful. Or have your dog sit in it. Or put a rego sticker and number plates on it. It’s almost 200kg heavier than a Jaguar XKR-S and it’s even heavier than Maserati’s all-steel GranCabrio.

That heft, largely introduced to keep things on an even keel over bumps and to cool the monster M motor, doesn’t seem to worry the M6 Convertible too much in a straight line. It will hit 100km/h in 4.3 seconds, burst through 200km/h in 13.1 seconds and, with de-limiting, will run out to 305km/h in a sustained burst of violence.

AMG and M are engaged in a power struggle that Audi is about to rejoin (having moved on from twin-turbo versions of Lamborghini V10s), so 412kW and 680Nm don’t seem as impressive on paper as they probably should.

Take it from us, they are big numbers. Very big numbers.

It’s an engine that’s been written about extensively here before (in its M5 guise), so we’ll refrain from going into too much detail. Nevertheless, it’s worth mentioning that every last scrap of its torque peak is available at only 1500rpm and the thing still revs to 7200rpm. And, what’s more, it has two (two!) twin-scroll turbochargers nestled in the 90-degree vee of the 4.4-litre V8 block.

You can rightly expect plenty of M5 bits to lurk beneath the M6 Convertible. Attached to the engine is the M5’s dual-clutch seven speed gerabox and it pumps its drive through the constantly variable M differential sitting between the rear wheels.

It also comes with an adjustable traction control system, an adjustable gearshift speed (and harshness) system and launch control. Unlike its predecessor, you an even use the launch control twice in the same hour.

It stops all of this with 400mm front discs, clamped by six piston calipers and, at the rear 396mm discs with, curiously, a single piston caliper. They sit inside 19-inch wheels and tyres, though there’s a 20-inch option, which most will take up if they also tick the box for the carbon ceramics (with 410mm front discs) that save 19.4kg (almost one per cent of the kerb weight).

It’s possessed of a beautiful interior. The curve of the dashboard lets the driver know he (or she, sorry) is the one it’s really all about, bending down from the front passenger’s side of the dash to focus on the driver’s seat.

But in either seat the cabin is a fabulous place to spend any time -- rich in leather, alcantara, carpet and high-quality plastics, it’s highlighted by a very fat steering wheel (too fat?) and BMW has grouped all the important switches around the gear lever.

The rear seat accommodation is actually quite useful -- even for adults. You do draw the short straw if you climb in when the roof is down, however, especially at highway speeds. It lacks an all-window down/up button, but the real crux of the rear-seat discomfort is that genuine no-buffet driving can be had only in the front seats with the wind blocker in place. And that gobbles up the entire back seat.

It’s more than acceptable without it in town, but it’s a bit more painful on the highway.

Still, putting up the wind blocker means you have an excuse to leave behind those who might want to put things in your boot. Because you don’t really have one. The roof’s hole is permanent, large and intrusive and the boot space is severely compromised. So leave the passengers at home, throw your bags beneath the wind blocker and be done with it.

Mercedes is a bit hit and miss here. The SL63 AMG has just launched in Europe with its own twin-turbo V8 but the standard SL upon which based on isn’t as good as it might be. It’s not bad or unreliable, it just doesn’t have the handling prowess you’d expect from Benz’s traditional flagship. That, and there are only two seats in it. And the roof is metallic.

If you want a hard-core handler in convertible form at Benz, you have to look upstream to the SLS Roadster and, again, it’s only a two-seater. Diddums.

There is the E-Class convertible, but it’s really a C-Class in drag (check the wheelbase).

It’s similar over Audi way, with the S5 aimed at a market far lower down the tree than this (even though it’s a true four seater) and no convertible version of the A7 in the wings. There’s an R8, but a mid-engined supercar with the roof cut off is hardly the same style of machine.

The obvious competitor is still from Germany with Porsche just launching the Cabrio version of its new 911 – and it’s a cracker.

It doesn’t match the M6 for midrange gristle, but it makes up for it by being lighter, more rigid and better balanced in its handling, even if its rear seats are, at best, part time options.

There’s a less obvious rival, too, in the Jaguar XKR-S, which has a belting supercharged V8 up front, odd looks (with too many vanes and fins and vents to be coherent) and almost 200kg less mass to tote around everywhere. Yet, somehow, higher fuel consumption. Go figure.

You could go the Aston Martin road but Aston’s offerings here are dated in extremis and have V12 power that doesn’t cut it for torque or throttle response. At least there’s a newish one on the way… New-ISH…

And it does it in any gear and from any engine speed, even idle. It’s a brilliant sound; brutal, menacing, unrelenting and it seems inexhaustible. Indeed, the M6 smashes the conventional thoughts of what a car that looks like this ought to do in a straight line, punching to 100km/h in 4.3 seconds, hitting the standing kilometre in 22.1 seconds and jetting across the 80-120km/h sprint in a quite-special 3.8sec.

It's also got a gearbox so slick you don’t notice it’s there most of the time -- exactly the opposite of the old unit that you cursed at almost every shift.

You can also adjust the tempo of everything to be more comfortable, more eco-friendly (like throwing bricks in the Grand Canyon when you’ve just bought a two-tonne, twin-turbo V8 to be driven for only half the year, but there you go), more sporting or more individualized.

That last option is pretty good, because you can give it softer suspension, harder throttle and midrange steering weighting, for example, if the road suits it. Sometimes it just does, and everybody knows the sportiest suspension settings often don’t grip the hardest in the real world.

The fear with a cloth roof this big is always scuttle shake – that wobbling of the windscreen and mirror that indicates the job is too much for the chassis’ rigidity. And it doesn’t start well for the M6 Convertible, because it initially has a surprising amount of shake over very small bumps. Then something odd happens: that little shimmy in the mirror as the tyres walk over a manhole cover is as big as the shimmy ever gets, regardless of the size of the bump or the speed you hit it at.

It's then that the car really starts to make sense. It’s very, very strong and the handling is superb. It takes some time to develop confidence in its ability to be chucked and stuck, but the M6 soft-top never fails to deliver. You can point it at long, bumpy corners and the tyres can be screaming from the pain in their fingernails from hanging on, yet the chassis itself is as happy as Larry.

And something else happens. While it’s not as crisp on turn-in as the M5, the slight movement in the chassis helps the M6's steering deliver more feedback to the driver. Thus over faster or bumper bends, it’s actually a more communicative front-end (once it’s settled into a corner).

BMW has clearly aimed the core setup towards everyday driving, more than absolute hard-core belting, but then it adds the adjustability to the suspension so you can have it both ways, sort of. And it works, giving a superbly absorbent ride at town and highway speeds and better-than-expected body control when you push the car harder. And the harder you push it, the more confidence you show in it, the more it rewards you.

The outright grip levels are stupendous and reaching the outer limits of them requires thought but no real commitment, so progressive and communicative is the steering.

Dropping the roof leaves you open to the devil’s own engine note, but you don’t feel any wind buffeting until you’re well over 160km/h and even then, the awkward wind blocker behind the seats calms it all down.

The issue is that it effectively turns the four-seat convertible into a two-seat roadster, but a roadster with a four-seater’s compromises. The roof flies up and down in 19 seconds on the move so you don’t get trapped at the lights but the permanent hole in the top of the boot leaves the M6 with a comically small and oddly shaped boot space.

That doesn’t stop it being the fastest open-topped four-seater BMW has ever built and it’s probably the best. It’s a damned impressive thing, with huge comfort, tremendous speed and a thumping soundtrack… So let's forget about practicalities shall me…

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