Overall rating: 3/5
The BMW M4 Coupé (and its M3 Saloon brother) is a fast, agile and simply brilliant super-coupé. The M4 Convertible is all of those things, but ruined by a heavy, unattractive convertible hard-top.
In the Metal:
Unlike some previous generations of BMW M-cars, there is simply no mistaking the current M4 Coupé (or M3 Saloon) for any more humble variant in their respective ranges. The M4's body is pumped up to the point where you would think the gym instructor would be advising it to take things a bit easy and lay off the creatine. Wheelarches are bulkier and wider, there is a distinctive power-dome in the bonnet and, if you were in any further doubt, the quad-exhausts at the rear give the game away entirely. Standard wheels are 18-inch in diameter, but our test car ran on staggeringly gorgeous anthracite grey 19s, which just barely contain the overfed forms of the massive (optional) carbon-ceramic brakes with their louche gold-painted calipers. Yup, this is a car that talks the walk it's about to walk, no question.
A shame then that the convertible roof just ruins the lines. It's not an issue when it's folded away, but when up and in place (which let's face it, will be most of the time on our roads, with our weather) it just looks awkward compared to the much more slinky silhouette of the standard M4 Coupé. It's the way the roof rises up slightly too high at the apex of the rear window that does it - that and the long, flat rear deck that must be there to accommodate the roof when it's folded away.
Not only does the roof ruin the styling, it also does terrible things to the M4's weight. Never an especially light car to begin with, the change to open-top motoring has revised the M4's kerb weight upwards by a staggering 250kg. That's like carrying around a couple of prop-forwards at all times. The problem isn't so much the roof and mechanism (which do weigh a not-insignificant 60kg by themselves), but rather the extra strengthening and bracing that are required to stop the now-roofless M4's body and chassis collapsing like a half-eaten tortilla. Weight and complication were once anathema to the single-minded BMW M GmbH, No more, it would seem.
At least there is compensation in the cockpit. The standard 4 Series cabin is decent enough of itself, and is surprisingly spacious and practical for such an overtly impractical car, but here it's enlivened further by a sheaf of M-accessories, from the distinctive three-spoke steering wheel to decadently upholstered seats with butter-soft tan leather and lots of lovely contrast stitching around the place. As a location in which to spend time, it's pretty nice.
If ever a car were dominated by its engine, it's the M4. Turbocharging was frowned upon for years by the fastidious M-division's engine experts, but these days the efficiency gains just can't be ignored. So the M4 puffs in air through artificial aspiration, but it does so in a manner alien to most turbos. The redline is a very high 7,300rpm and the six cylinders whip themselves into a cacophonous frenzy in their race to get there. There is little to no turbo lag, except when accelerating from low speeds in a high gear, and everything is done to the accompaniment of a basso throb that reverberates around the cabin like Thor's bass-line.
Ah, it's fake. Or at least a portion of it is. Keep the engine in Sport or Sport+ modes (surely the default setting for an M-car?) and a clever electronic system kicks in to add extra layers of engine noise via the stereo speakers. Well, I say noise but mostly it really is just an extra bass note, as if the engineers missed the E93 M3's old 4.4-litre V8 engine and wanted to recreate the sound. It's a shame for two reasons. First, there's no need for it - although muffled somewhat by its turbochargers, the six-pot does emit a very pleasing, raspy roar when pushed hard (do so with the engine in Efficient mode to dial down the effect of the computer noises...) and secondly, it is yet another mark of how far BMW M has moved away from its once lofty position of purity (X5M, X6M, we're looking at you...).
The handling and ride combo though is mostly excellent. Yes, it's stiff but the convertible has necessarily softer suspension responses to allow for the extra weight and the need to keep the body from flexing too much. Even on the 19s, in Sport mode, it's only over really savage surfaces that you start to feel the need for something softer. The three-mode steering (Normal, Sport and Sport+) does its best work in Sport mode, which seems to offer the best balance between feel and weight. Sport+ adds too much weight and artificiality and Normal is just too light.
There is a problem though. Almost all electrically-boosted power steering systems have a slight but noticeable dead-patch just around the centre point of the rack, where the steering is deciding whether or not you need any help to turn it and just how much to provide. The M4 Convertible's inherently more flexible body makes this feel worse, and thus the steering, which should be as sharp as one of Marco Pierre White's steak knives, feels occasionally distant and even a touch shuddery. Yet another victim of convertible malaise.
At least the gearbox remains close to perfect. Seamless and fast in automatic mode, quick-reacting and full of little feedback sensations when using the manual paddle shifters, it even has the bonus of being more efficient than the manual, cutting some useful extra figures from the fuel consumption and CO2 emissions figures.
The M-Differential is also present and correct, parcelling out power to the rear wheels in precise packages, or allowing you to execute lurid, smoky power slides at will. Your choice.
What you get for your Money:
Prices start at €108,300 on-the-road for the manual version of the M4 Convertible, which is about €7,000 more than the coupé. We expect few buyers to go for that, instead opting for the dual-clutch automatic. That costs from €112,896 on-the-road. Standard equipment includes the clever differential, fine-grain leather and a plethora of buttons that allows you to tweak the responses of the throttle, gearbox, differential, dampers and steering. There will, of course, be ample opportunity to decimate your wallet with bespoke colours, nicer leather, carbon trim, those ceramic brakes (which are utterly tireless and strong) and more besides.
It's probably clear by now that we're not that keen on the idea of an open-top M-car, but to give the M4 its due, it manages the airflow around and over its body with typically Teutonic precision. Roof down, windows up and with the mesh air deflector (which covers the back seats) in place, we managed an easy (and entirely legal, m'lud) 210km/h cruise on the derestricted Autobahn just outside Munich. Although the wind noise obviously rises at that kind of speed, buffeting in the cabin is kept to at worst a stiff breeze and conversation is still possible between driver and passenger.
Again, given some dues, roof up the M4 is perfectly cocooned and silent inside at a similarly fast cruise. Given the time-warp way the engine gathers speed and the car's rock-steady attitude at high speeds, it is a bewitchingly fast and enticing way to cover ground.
The problem is that this car really shouldn't be made. It's a sop (albeit a sop worth some 60,000 sales since the first M3 Convertible of 1988) to affluent, sun-state dwellers who care more about being seen in the highest spec car possible, rather than getting the car that's the best to drive. BMW boasts that the convertible retains all of the M4's race-bred features such as special oil coolers, a carbon-fibre strut brace to stiffen the front suspension's resolve and clever aerodynamics. All of which will be mostly lost on most of the car's customers.
To our way of thinking, if you want a fast, capable convertible then the far cheaper but seriously capable 428i provides all the BMW you need, and with the optional M Sport kit is damn near as good looking as the full-fat M-car. If you want an M-car, then you really should be buying in to the proper M experience and getting the lighter, more focused coupé.
That the M4 convertible retains 99 per cent of the standard coupé's ability and performance is a remarkable testament to BMW's engineering prowess, but there is no getting away from the fact that it is heavy, expensive and compromised. We'd have the standard M4 Coupé, thanks.*
*Actually no, we'd have the even more muscular, more hard-core M3 Saloon, thanks.