Power certainly isn't an issue, because the M4 convertible is fitted with the same 425bhp, twin-turbo, six-cylinder engine as its hard-top counterparts. The same twin-clutch DCT auto gearbox is available as an option, too.
Choosing the wind-in-your-hair approach does – as usual – come with a weight penalty; the drop-top is 200kg heavier than the M4, thanks in part to its complex folding metal roof. This means it takes a little longer to hit 62mph (4.6 seconds instead of 4.3).
It struggles in BMW M-car Top Trumps, then, but at £60,730 the M4 convertible has a better chance against rivals such as the more expensive, slower Audi RS5 Cabriolet and two-seater Jaguar F-type V6.
What’s the 2014 BMW M4 Convertible like to drive?
Plant your right foot hard and you'd be pretty hard-pushed to notice the small difference in the official figures between the faster M4 and this convertible, particularly from a rolling start. The engine pulls strongly from around 1800rpm all the way to its redline, and is eager to rev.
The noise that accompanies the rabid acceleration will split opinion. One thing's for sure, there's plenty of it, but with the roof closed the majority of it comes through the M4's speakers. Fold the roof away, though - which takes 20 seconds and can only be operated at less than 8mph - and the exhausts take over, bellowing loudly on full throttle and emitting fierce cracks on gearchanges.
Our test car was fitted with BMW's optional (£2645) twin-clutch automatic gearbox, which provides instant, undetectable changes when left to its own devices, and always seems to be in the right gear, no matter what the driving situation.
Use the wheel-mounted paddles for manual changes, and there are three stages of severity available. It's best left in its calmest setting, where the changes are nearly as sharp, but the shifts feel less violent from behind the wheel – in the quickest mode the auto ’box really thumps home each new ratio.
As with its gearbox, the M4 convertible's steering also has three settings - 'Comfort', 'Sport' and 'Sport Plus'. Across all three the steering feels quick and precise, and you get a good sense of when the front tyres are struggling. Sport mode is the best compromise: Comfort feels a little light, and there's too much unnecessary artificial weight in Sport Plus.
The adaptive suspension gets the same level of adjustability. In its hardest setting, the sense that you're carrying extra weight around is quite evident, especially in tight corners. Even so, the convertible still manages to control its body mass well when changing direction sharply. The huge grip on offer and trick rear differential also provide plenty of confidence when trying to push on.
However, removing the M4's roof doesn't do the ride quality any favours, because large potholes, sleeping policemen and sharp-edged ridges all send shudders through the convertible's body.
Ultimately, the M4 convertible is a very capable open-top, but if handling poise is a priority, the coupe's better structural rigidity helps it turn in harder and stay more settled over mid-corner bumps. It still feels more composed than the Audi RS5 Cabriolet and Jaguar F-type V6 though - partly because the entry-level Jag misses out on the adaptive dampers that are standard on the V6 S and V8 R.
Reign in all the various drive modes, and cruising in the M4 convertible with its metal roof closed is a relaxing experience, because there's very little wind or road noise allowed inside the cabin.
It's impressive with its roof down, too. There's little buffeting when its four windows are up and almost none with its optional wind deflector fitted across its rear seats. The deflector is easy to put in and take out, too.
What’s the 2014 BMW M4 Convertible like inside?
BMW demands you stump up a fair amount of your hard-earned for M4 convertible, but it does feels worth it.
Electrically adjustable, leather sports seats are standard, which feel high quality and do a great job of holding the driver and front passenger securely in place through fast bends.
Setting the wheel and seat to a comfortable position is simple work and the M4's aggressive bulge on its bonnet - visible through the windscreen - is a constant reminder of its clear sporting intent.
While there's enough head- and legroom for a couple of tall adults in the front, a pair of adults will struggle more for space in the back seats with the roof closed. Shoulder room is tight and their knees will likely be touching the front seat backs, especially with a tall driver. With its air deflector in place, the M4 convertible effectively becomes a two-seater.
Boot space is also limited. Roof up, the convertible offers 370 litres, but should you want to fold it away, that's reduced to a short, narrow 220 litres. That's enough for the weekly shop on a rainy day, but barely enough for a suitcase on a sunny one. It's also disappointing that the folding rear seats that leave a narrow opening through to the boot cost an extra £170.
However, all of the best bits of BMW's market-leading infotainment system are present and correct. Its superb larger-screened 'Professional' system is standard, via which you operate the sat-nav, DAB radio and Bluetooth menus using the slick iDrive rotary controller located between the front seats.
Beyond the infotainment, standard equipment is generous. 19-inch alloy wheels, front and rear parking sensors, electric folding door mirrors and heated front seats all feature. Options include Air Collar (£360), which gives added comfort in cold weather by blowing warm air onto passengers' necks.
Should I buy one?
While not as sharp as either the M3 or M4, this convertible version nevertheless puts on an impressive handling display when judged against open-top rivals. Those with an eye on running costs will find its official 32.5mpg and CO2 emissions of 213g/km competitive, too.
The automatic-only Audi RS5 Cabriolet costs around £6000 more to buy. It equals the M4 for cabin quality and equipment – and is more powerful – but it isn't as quick in a straight line and is even heavier, so feels considerably less agile through corners.
The Jaguar F-type V6 S is £4000 more expensive, and is also slower, but offers similar levels of involvement on a meandering B-road. The Jag's boot space is even stingier, though, and there's room for only two to enjoy the moment.
What Car? says…
BMW M4 Convertible