BMW M4 ConvertibleThe BMW M4 Convertible is the best M3 Convertible in 26 years, but drivers will still prefer the M4 Coupe and M3 saloon.

RICHARD AUCOCK | AUGUST 2014

BMW’s M GmbH engineers are a committed bunch who are obsessed with making sure their brand’s new cars live up to the heady standards set by their predecessors. With the new M3 saloon and M4 Coupe, they’ve done that, despite bosses throwing them challenges such as using turbochargers and improving fuel economy.

And for their next trick? Make a driver’s car of the M3 Convertible. Four generations of the open-top M3 have been made to date, and 60,000 people have brought one, so it’s a popular idea. Today’s 4 Series Convertible thus becomes M4 Convertible and the fifth generation in the 26-year model line.

It sure looks the part. The roof is better integrated than it’s ever been and, roof down, the low and wide rear deck looks great, set off nicely by the M quad exhausts and diffuser-laden bumper. No missing the M bonnet bulge and aggressively sculpted front bumper either.

UK cars get 19-inch alloys as standard. Ideal for filling the M-specific flared wheelarches that make it look so potent. It has lots of purpose and plenty of streetside show, particularly when started up and those four exhausts signal its arrival. Big ticks before you set off then… but can they continue?

BMW M4 Convertible 2014What’s the BMW M4 Convertible like to drive?

Using BMW’s wonderful torque-laden 3.0-litre straight six turbo, the M4 Convertible is much easier to drive quickly than the peaky V8 M3 Convertible. For many of the target market, this will immediately appeal, particularly when paired with the £2645 M DCT seven-speed automatic that most buyers will option. It responds to the accelerator with little delay and you rarely need to use the full 7500rpm rev range to release its best (boy, is it fast when you do).

It accelerates to 62mph from rest in 4.6 seconds. This is rapid: not only is if faster than the old V8 M3 Convertible, it’s also quicker than the old M3 Coupe too. With M DCT, it’s even faster – launch control sends it to 62mph in 4.4 seconds.

Power delivery was, in the rain of the test drive, often traction-limited. A very effective traction control system releases as much drive as possible without interference being too obvious, but it’s an indicator of how readily the engine is to deliver its 405lb ft of torque. Indeed, with some swift, responsive downshifts from M DCT, it’s also not obviously turbocharged – turbo lag shouldn’t be an issue.

Driving dynamics should be ranked in two parts – roof up and down. Roof up, it’s often hard to detect any loss of structural rigidity; the odd shimmer is there, but infrequently. Choose Sport Plus for the steering, from the M4’s famously multifaceted adjustment buttons, and it’s both nicely weighted and crisply linear in response, and Adaptive M suspension is faithful and balanced. It rides well too, and body control is excellent despite the eye-opening 1750kg kerbweight (and that’s 60kg down on before, too…).

Roof down, it’s much less rigid. Shimmers through the windscreen and bulkhead are obvious, and you’ll feel vibrations through the seats. The flex doesn’t spoil steering response too much so it still seems sporty, but the rest of the car lags behind a bit, feeling muddier the faster you drive. M engineers, you sense, would’ve probably driven most miles with the roof up: there’s not a lot they can do with the roof down flex (even if it is much better than anything that’s gone before it).

BMW M4 Convertible 2014Is the BMW M4 Convertible a driver’s car at last?

The M4 Convertible seems eager but, compared to the M4 Coupe and M3 saloon, it’s less pure. It’s not as agile, a touch more top-heavy and there’s more interference and less fingertip feel. It’s still good, as all the M componentry that’s so good in the other two remains, but the platform it all works from is not quite as ideal.

Drivers should certainly keep the roof up as the compromises are even more pronounced roof down. Driving it like an M car here is harder work and less satisfying. Best here to go 6/10ths and enjoy the engine noise and exhaust rumble instead, the latter usually only available to pedestrians. The engine rumbles and rorts roof up too, which seems purposeful; some feel it’s a bit artificial but there’s no denying the impression of potency it brings.

For those drivers, there is specific appeal in other ways from the M4 Convertible: the allure of such a powerful open-top four-seater is clear, particularly one that’s so bluster-free roof-down. The roof goes up and down in 20 seconds – on the move if you keep speed below 10mph – and the pillarless side windows give a classic coupe feel with the roof up. They make it light and airy inside as well.

The bits that appeal to drivers of the M4 Coupe and M3 saloon are still in place inside, from the lovely M steering wheel and M dials (love the warmup-dependent rev counter LEDs) to a fantastic set of bolstered (albeit slightly high-set) seats. These can be enhanced by a neck warmer hot air system called Air Collar. Back seat drivers will be impressed by the space available, if not the access and egress, and although the 370-litre boot reduces to 220 litres roof-down, a clever access system makes loading it easy. It even has a through-load system, should drivers be into DIY.

BMW M4 Convertible 2014MR verdict: 2014 BMW M4 Convertible

We still prefer the M4 Coupe and M3 saloon to the M4 Convertible. They are five-star cars; this gets four stars, because the roof does compromise it as an M car. But for those unconcerned with ultimate M spirit and happy to just enjoy the M feel in a powerful, good-looking four-seat convertible, it will appeal, even at £60,000.

Rivals: BMW M4 Convertible

  • Audi RS 5 Convertible
  • Porsche Boxster
  • Mercedes-Benz E-Class Convertible
  • Mercedes-Benz SLK

The aged Audi isn’t very good as a coupe and cutting the roof off certainly doesn’t help things. The engine is exciting though, and it looks muscular, which will be enough. Missing a trick, Mercedes-Benz doesn’t offer a C-Class Convertible (hey, it took years to bring the C-Class Coupe to market), so a more powerful E-Class Convertible will have to do. Or maybe an SLK, to rival the Porsche Boxster two-seat alternative.

Specification: BMW M4 Convertible

Engine: 3.0-litre turbo petrol
Gearbox: Six-speed manual
Price from: £60,730 (M DCT: + £2645)
Power: 431hp
Torque: 405lb ft
0-62mph: 4.6 seconds (4.4 seconds M DCT)
Top speed: 155mph
MPG: 31.0 (32.5)
CO2: 213g/km (203g/km)