What’s Hot: Sharp handling, beautiful style, engine never runs out of pull.
What’s Not: Weight blunts performance, brittle ride, pricey.
X-FACTOR: Not as finely-honed as its fixed-roof sister, but plenty enticing all the same.
Vehicle Style: High performance convertible
Price: $178,430 (plus on-roads), $189,380 as-tested.
Engine/trans: 317kW/550Nm 3.0 turbo petrol 6cyl | 7sp twin-clutch auto
Fuel Economy claimed: 8.7 l/100km | tested: 15.0 l/100km
Take a great sports car and cut off its roof. Ruined, right?
Exhibit A: the Audi RS 5 Cabrio. While the RS 5 Coupe is fast and grippy and begs for a spanking, its roofless sibling has the torsional rigidity of a damp phonebook and feels unhappy on anything bumpier than a bowling lane.
And so we introduce Exhibit B: the BMW M4 Convertible. It’s a sharper instrument than the RS 5 by a wide margin, and, sitting low and fat on muscled-up haunches, is surely one of the better looking premium convertibles.
Being a drop-top, it's also sexy by definition. And being an M4, it is sinfully quick.
But it's not all roses: it's nudging 200 'big-ones' by the time you get it on road, and there are some compromises you'll be living with too.
- Dual-zone climate control, heated and powered front seats, Air Collar front headrests, keyless entry and ignition, leather upholstery, bi-xenon headlamps, surround-view parking cameras, front and rear parking sensors.
- Infotainment: 8.8-inch colour display with iDrive controller, Navigation System Professional, AM/FM/CD/DAB stereo, USB audio input, Bluetooth telephony and audio streaming.
- Options on test vehicle: Heated steering wheel, head-up display, Internet connectivity, ConnectedDrive Freedom package, LED headlamps, lane-keep assist.
The M4’s metal roof drops in just under 20 seconds, can be deployed at speeds up to 18km/h and stacks away neatly in the boot.
Stacks neatly, mind you. Not compactly.
There’s only 220 litres of luggage room under all those roof panels, and removing your gear isn’t easy.
BMW thankfully equips the M4 with a hydraulic mechanism that raises the entire assembly of stowed roof bits so that you can access the boot more easily, but we shudder to think about how much weight that feature alone has added to the car.
Keep the roof up (which kind of defeats the purpose of a convertible, we suppose), and there’s more luggage room to play with.
The rear backrests also fold down to reveal a fair-sized cargo pass-through, which is something not always found in a convertible.
Seat heaters are standard and so are a pair of warm-air blowers (BMW dubs them 'air collars') mounted at the base of the front headrests.
With the roof and windows down, wind buffet isn’t too bad.
With the heated seats, climate control and air-collars cranked up it’s a more than tolerable environment.
Plus, with the exhaust crackle and turbo whistle far more audible with the roof down, it’s the best way to experience the M4 convertible.
Raise the roof, and the benefit of a hard-top over a soft-top becomes apparent.
Wind noise disappears, and the cabin looks and feels almost just like the M4 Coupe
ON THE ROAD
- 317kW/550Nm 3.0 litre twin-turbo petrol inline six
- Seven-speed twin-clutch automatic, rear-wheel drive. Six-speed manual no-cost option.
- Multi-mode steering, transmission and engine response modes, MDM traction control mode allows greater slip angles.
- Adaptive multi-mode suspension, adjustable dampers.
- Ventilated disc brakes.
From its twin-turbo 3.0 litre inline six, to its carbon fibre tailshaft to the active rear differential, the M4 Convertible gets the same superb mechanical package that the M4 Coupe (and by extension, the M3) enjoys.
The difference, however, is in weight. A whopping 253kg of it separates the Coupe from the Convertible.
A lot of that extra fat comes from the roof mechanism itself plus the pop-up roll-over bars, but the M4-specific chassis reinforcements needed to brace the convertible against that 317kW/550Nm engine adds even more mass.
And the effect of that weight is blunted performance. The M4 Coupe hits 100km/h from standstill in 4.1 seconds, but the Convertible takes 4.4.
Four tenths of a second may not sound like a whole lot, but it is noticeable: the electric 'alertness' of the Coupe is dulled just slightly.
Let's be clear: the M4 Convertible is still scaldingly fast in a straight line, it's just not as fast as the tin-top.
That extra weight has a more pronounced effect on handling, however. The M4 Convertible doesn't feel as sharp or as willing to change direction, and you have to fight its extra momentum at times.
The M4's active rear differential and its ability to vector torque between each rear wheel aids turn-in, but the laws of physics always win. If you want the hotter performer, you need the M4 Coupe.
And despite the extra reinforcements, the M4 Convertible still suffers from some chassis flex and scuttle shake. Roof-down, the steering column shimmies in your hands and the windscreen frame vibrates over bumps.
Not as badly as the RS 5 Cabriolet, but still not great. The firm suspension tune and low-profile tyres don't help quell the vibrations either.
Comparisons to the M4 Coupe fare worse though. The Coupe is textbook RWD performance car, with superb balance and an eagerness (some might say it's over-eager) to step the tail out.
The Convertible feels a lot more dulled in its response, like a hurdler who's had a few too many doughnuts.
However, like all good drop-tops there is one winning factor to the M4 Convertible - a virtue that no coupe can quite match.
Its great virtue is the sheer joy of top-down motoring.
Whether it be a winding forest road early on a Sunday morning, or a beachside boulevard at sunset, or the neon-lit concrete canyons of a city at night, the M4 Convertible with its roof retracted makes every drive an event; not just an exercise in going from A to B.
And it sounds much, much better with the roof down.
While the exhaust note of the M4 coupe sounds completely synthetic from within the cabin, the M4 Convertible reveals a truly rorty and melodic straight-six noise when driven topless.
ANCAP rating: The BMW 4 Series convertible has yet to be crash tested by ANCAP
Safety features: Stability control (switchable), traction control (switchable), ABS, EBD, brake assist, cornering brake control.
All occupants receive three-point seatbelts and headrests, though the folding roof means there's no head airbag protection for rear passengers - just dual front and front side 'bags.
RIVALS TO CONSIDER
For a comparable four-seater convertible with big power, Audi is pretty much the only direction you can look right now.
Mercedes-Benz has yet to launch its C 63 Convertible, so for now the M4 Convertible's sole true rival is the Audi RS 5 Cabriolet.
TMR VERDICT | OVERALL
If you're focused purely on performance, the M4 Convertible won't make much sense. It costs $12,000 more than the Coupe, weighs more, flexes more and is slower.
So, on a raw bang-for-buck comparison, the spearing M4 Coupe wins hands down.
But it has other charms, the M4 Convertible, because it is just that - a convertible.
And it is, really, despite being shaded by the Coupe, one incredibly rapid conveyance.
So, there's your choice. If you want flying wind-in-your-hair freedom AND a rapid performance machine with screen idol looks, the M4 Convertible has those boxes pretty well ticked.
Be prepared to pay for the privilege of that convertible roof, though.