DESIGNING a convertible must be one of the most daunting jobs in the automotive world. Getting it to look good is the easy part trying to keep it from flexing all over the road must sometimes drive the engineers to despair.

To BMW Australia’s credit, it chose some of the more demanding hinterland roads of northern New South Wales and south-east Queensland for the local press launch of the new fourth-generation 3 Series Convertible, but its confidence was well-founded.

Even over these winding, undulating and often bumpy roads – the sort of roads that would have rattled a Saab 9-3 convertible to pieces – the latest version of the country’s top-selling luxury convertible was in its element, lapping it all up with the sort of dynamic poise you might expect of a car with a roof.

There was virtually no scuttle shake at all and even the most savage of mid-corner bumps would provoke little more than a flutter through the steering wheel. Most coupes would aspire to such structural integrity, let alone a bath on wheels.

The so-called 3CC – it now has a folding steel roof instead of the previous fabric set-up, making it more of a coupe-convertible – arrives at a premium of about $12,000 over the equivalent coupe models. It would be all too easy to say that’s a lot to spend to have the roof removed, but (even ignoring the tax component) this is no simple chop job.

BMW’s designers and engineers have not only managed to produce a dynamically satisfying convertible – no mean feat by itself – but have provided numerous neat touches that would make living with the 3CC a pleasure.

The three-section roof not only folds away in just 22 seconds, either from inside the car or by remote control within eight metres, but it tucks away impressively into the top level of the boot. Even with the roof down, you can accommodate a set of golf clubs, thanks to a wide trunk-through facility in the back seat.

The roof can also be folded back half-way, allowing unhindered access to the boot.

Another neat feature is that the rear seat back folds down so you can put bags and other cargo in the back without sweating over what it is doing to your superb leather upholstery.

Of course, there is also a pair of built-in roll bars tucked away behind the rear seats that are instantly deployed in the event of a roll-over, not to mention seat-integrated side airbags to protect the front occupants’ heads even when the roof is down.

The only negative we found is the amount of ‘booming’ you get when the roof is in place, which does not exist in the 3 Series sedan, for example. Caused by air pressure, we found this resonance to be a little uncomfortable.

In terms of specifications and equipment levels, the two Convertible models are identical to their Coupe siblings.

The entry-level 325i Convertible ($94,900), with its smooth 160kW/250Nm six-cylinder ‘atmo’ engine, is a magnificently lithe and well-balanced machine that belies the extra 200kg over the Coupe.

It feels light, yet solid, with a superb inherent balance that makes driving a pleasure. Apart from a slightly lazy low-speed kick-down from the six-speed automatic (add $2600), the 325i provided an utterly enjoyable and comfortable driving experience.

If performance is what you are after, the 3.0-litre twin-turbo 335i Convertible – $121,500, with the addition of bigger wheels, adaptive headlights, parking sensors, sport seats with lumbar support, top-level SatNav and upgraded sound – provides that in spades.

But not even the demands of taming some 225kW of power and a chassis-twisting 400Nm of torque can unsettle this car – the 335i simply roars through the most demanding roads looking for the next corner to consume.

Both the power and response of the twin-turbo engine are superb and, as with the 325i, the steering makes you feel connected to the road while the brakes are rock-solid.

BMW has certainly raised the stakes in the luxury drop-top segment.