We've already driven the M4 Competition Coupe, which impressed us with its more focused approach and incredible capability on both road and track. But will the removal of the M4's roof prove to be the making or the breaking of this brutish sports car?
In the metal
Roof design aside, this is still an M4 Competition with all the M4 Competition styling features. Chief among those is the big grille, which has ruffled plenty of feathers among car enthusiasts everywhere. In the M4, the frameless 'kidney' grille is all black with horizontal bars, while the front bumper is an angular collection of fins and air intakes.
It's about as unpopular as front-end designs get, but BMW has decided to own it for the 4 Series and the M3 and M4 models. Opinion is divided in the CompleteCar.ie office, but this writer thinks it kind of works. It isn't subtle or understated, but then nor is anything else about the M4.
Not only does it come with mismatched wheel rims - 19-inch at the front and 20-inch at the back - but there's a black skirt all the way around with extended sills and a deep rear diffuser. That also houses the quad exhaust tail pipes, which measure a massive 10cm in diameter and leave no doubt that this is a high-performance vehicle. There's also a handful of aerodynamic features, including huge gills around the front wheel arches, that hint at the car's power and performance.
One feature the drop-top M4 misses, however, is the coupe's rear spoiler. With no carbon-fibre roof to channel air down to the boot lid, it just has a kind of built-in ducktail at the back. But of course the biggest difference is that roof. Where the coupe has this gloriously rakish rear window, the convertible has a flat deck that's replaced with a curved canvas hood when the roof is up. As you'd expect, there's an electrically operated framework under there that retracts the roof at the touch of a button.
In many ways, that's a big advantage. It means you can enjoy some top-down motoring when the sun is out, and that allows the M4 to become a genuine four-seater. As in the M4 Coupe, legroom is surprisingly abundant, but headroom is the only catch. When the roof is stowed away, however, headroom suddenly stops being such an issue.
That aside, the M4 Convertible's cabin is more or less identical to that of the coupe. The dashboard is the same, with all the flecks of red and the iDrive infotainment system, plus the digital instrument cluster and the head-up display. It has the same quality, too, with switchgear that feels really chunky and substantial and precise. It's a delight, and one that feels as though it was properly thought through, right down to the last detail.
Our test car came with the optional M bucket seats, which suit the open-top sports car vibe perfectly. With beautiful swathes of carbon fibre and some soft leather upholstery, they are stunning to look at and surprisingly comfortable to sit in. Even long journeys won't be too wearisome. But they hold you in tightly, keeping you locked in position even when you're throwing the car around. Just be careful getting in and out because that can be quite an uncomfortable experience.
It's also worth mentioning the M4 Convertible's boot, which is noticeably smaller than that of the coupe at 385 litres.
We've already sampled the M4 in rear-wheel-drive Coupe form, but this Convertible model is more than just an M4 with a fabric roof. BMW has decided it will only offer the M4 Convertible in controversial all-wheel-drive guise. But we've tried the snappily named M3 Competition xDrive Saloon, and found it wants for nothing. So this drop-top M4 should be pretty spectacular.
And indeed it is. The M4 Competition rides more rigidly and changes direction more nimbly than the M3, and the retractable roof has made no great difference to that. You can feel the inherent stiffness of the car's body, even though it isn't quite as rigid as the Coupe, and while the suspension is just about pliant enough in its most supple setting, the Sport Plus mode provides even sharper body control to the detriment of ride comfort.
Not that the M4 needs to be any more responsive. Even with the settings turned down to Comfort, the handling is simply superb. The nose darts into corners at the slightest hint of encouragement from the steering wheel, and the car couldn't stop more rapidly if it hit a wall (Ok, calm down now James - Ed).
That said, the little Setup button on the centre console does have a discernible impact on the car's characteristics. Opt for Sport mode for the steering and there's a little extra resistance through the wheel, which adds nothing in terms of feel for what the front wheels are doing and makes little difference in terms of responsiveness, but it makes the car feel marginally more stable in your hands. The same goes for the brake pedal, which is almost completely devoid of feel, but becomes tighter and more direct when you change its setting from Comfort to Sport.
The engine settings also make a difference, with Efficient mode giving you the smoothest and most peaceful experience. That makes it perfect for urban traffic or motorways, where the eight-speed automatic gearbox helps to keep the noise at sociable levels and allows for more dignified progress.
If, on the other hand, you select the Sport Plus setting, the throttle response is instantaneous, and the gearbox drops down through the cogs to deliver as much performance as possible. That's great on a race circuit, or even on a good back road, but it's far from ideal in the middle of town.
The Setup button also allows you to fine-tune the M4's four-wheel-drive system. As standard, the car sends most of its power - all 510hp of it - to the rear wheels, with an electronically controlled clutch deciding if and when it should redistribute some of that force to the front. That's joined by a clever rear differential that splits the power between the back wheels. But if the mood takes you, you can change the settings so the car sends more power - or even all the power - to the back wheels. In effect, it's a four-wheel-drive system you can switch off when you want to go sideways on a racetrack.
And that's great, because it means all the purists worried about diluting the M4's more challenging characteristics can just switch the xDrive system off whenever they wish. While those who like the idea of more stability on the public road, and in poor weather, can leave the all-wheel-drive system firmly engaged. And those drivers will get to enjoy their car's full capability.
Because as well as making the car feel more secure in bad weather, the xDrive system also allows you to go very quickly indeed. With all four tyres helping to translate that enormous power output into forward motion, the M4 Competition xDrive will hare away from the line with the sort of alacrity stabbed rats can only dream of. A full-bore start will see this car race from 0-100km/h in 3.7 seconds, while the top speed is 250km/h. That makes the Convertible, which weighs almost 200kg more than the rear-drive Coupe, just two tenths of a second slower to 100km/h. That's an incredible statistic.
But although the xDrive system accounts for around 50kg of that weight difference, it has no apparent impact on the handling. The balance is glorious, there's no hint of understeer in fast corners and there's absolutely no sense that the front wheels ever receive any of the power. Until you put your foot down, at which point the car makes full use of its improved traction and simply disappears in search of the next horizon while you're forced back into your seat.
Special mention should also go to the M4's glorious 3.0-litre straight-six engine, which is creamy and refined at normal, everyday speeds, but turns into a complete animal when you want it to. Despite the turbochargers, it sounds feral and guttural and dirty in the way only a good sports car can. You can turn down the noise by switching off the active exhaust, but that seems a bit pointless. Get the roof down whenever you can and just enjoy the tunefulness with which a BMW engine can burn petrol.
What you get for your money
It won't come as a surprise to hear that the M4 Convertible is more expensive than its hard-top sibling. Prices start at €148,015, which makes the drop-top around €5,000 more expensive than the all-wheel-drive Coupe. With a few options, though, this is a car that costs well over €160,000, and then €5,000 doesn't seem like such a big expense. Certainly not for the freedom of open-top driving.
The M4 comes with plenty of equipment, too, including leather upholstery, the iDrive infotainment system and the head-up display. It also comes with a Harman/Kardon audio system, heated front seats and automatic climate control, not to mention the carbon-fibre interior trim and all the M-specific features that separate this car from the less powerful M440i xDrive Convertible.
The BMW M4 is an impressive car in any form, but removing the roof just seems to add that little bit of extra excitement to proceedings. It isn't quite as stiff, which will make it slightly more palatable on Irish roads, and it has the advantage of unlimited headroom whenever the sun chooses to shine.
That sounds like a minor advantage, but it only costs another few thousand euro, and it makes the car as comfortable at Mondello as it would be cruising past Maranello. And with the xDrive all-wheel-drive system fitted as standard, the M4 Competition Convertible really is a car for all seasons.