BMW reveals 2 Series Convertible

It's longer, wider and more economical, but BMW hopes being faster, too, will deliver the all-new 2 Series Convertible the same surprise success of the old 1 Series.

After the 1 Series Convertible found more than 130,000 homes worldwide, BMW's smallest convertible has now adopted a longer wheelbase, a wider cabin, a bigger boot and a more useful rear seat and a new, 2 Series name, too.

On sale in Europe from February next year and in Australia within months, the 2 Series Convertible will follow the same powertrain conventions as the cracking 2 Series Coupe range, spearheaded by the 240kW M235i version.

BMW claims its flagship M235i will set new benchmarks for agility in the segment, with its 3.0-litre inline six-cylinder turbo engine backed up by an eight-speed paddle-shift automatic transmission and M-tuned suspension.

Boasting a 5.2-second sprint to 100km/h, the M235i stretches out to a governed 250km/h top speed and swallows 8.5L/100km, all despite a dry weight of 1600kg.

It's 0.4 seconds slower to 100km/h than its hard-topped brother, but BMW puts most of that down to the extra 130kg (for the automatic) it soaks up in both underbody reinforcement and its folding cloth roof mechanism.

This engine spins like a champ in the coupe and there's no reason to believe it won't do the same in the convertible, even though it has to work a bit harder shifting more kilos. Beneath the power peak, the torque peak arrives at 1300rpm and stays at its 450Nm maximum until 4500rpm and then the power takes over, with all 240kW chiming in at 5800rpm and staying on station for another 200rpm.

It lacks for little in modern petrol-engine tech, with direct fuel-injection, of course, along with variable valve timing and the double VANOS variable camshaft control that was once the preserve of the bigger M cars.

It also scores a mechanical limited-slip differential and 225/40 R18 front tyres and 245/35 R18s at the rear, with M using the tyres to help it tune the balance into the car. A forged 19-inch wheel package is also optional.

The hero cabrio leads the rest of the droptop family by being 72mm longer than the old car (4432mm), 26mm wider overall (out to 1774mm) with the front and rear tracks pushed out by 41mm and 43mm respectively.

For those who suffered in the rear seats of the old car, the extra 30mm in wheelbase (out to an entirely grown-up 2690mm) should address some of the complaints, as should its extra 30 litres of luggage space (out to 335 litres), which comes complete with a wider boot mouth as well.

While BMW insiders admit it made a mistake by putting a folding-metal roof on to the Z4, it's made no such errors with the 2 Series, giving it a multi-layer cloth roof that can fold down or up in 20 seconds and can do it all at up to 50km/h – which is a remarkable speed for a roof parachute this large.

The flagship might have an M in front of it, but the core of the sales volumes are expected to come from the 135kW 220i and the 180kW 228i Convertibles, though the 140kW 220d diesel is expected to snare a firm footing in the European market.

The diesel will suit the cut and thrust of urban traffic, too, with 400Nm on offer to rank a strong second on family torque output figures behind the M235i to get it to 100km/h in 7.4 seconds. What's more, the torque arrives at 1750rpm and remains until 2500rpm, while it hits peak power at 4000rpm.

Quirky though a diesel convertible is, the lion's share of sales will be powered by the 270Nm (from 1250 to 4500rpm) 220i, which will reach 100km/h in 7.5 seconds. But while the diesel uses just 4.4L/100km, the 220i pushes that up to 6.2L/100km.

The 228i boasts a familiar powertrain that first saw work with the debut of the current 3 Series. The turbocharged 2.0-litre four-cylinder engine (which is essentially identical to the 220i's motor, but for tuning and software) delivers 350Nm of torque from an incredibly low 1250rpm, yet its power peak of 180kW stretches up to as high as 6500rpm.

That's all good enough to send the 1535kg 228i to 100km/h in a healthy 6.1 seconds while using just a trace more fuel than the 220i.

BMW claims all of the 2 Series Convertible models have around 20 per cent more torsional rigidity and 10 per cent more bending stiffness than the equivalent 1 Series Convertible, which should help the strut front-end and multi-link rear-end to deliver more precise handling. There are also pop-up rollover bars in case that all goes wrong.

The new convertible is strong on safety features, coming with adaptive headlights, high-beam assist to automatically dip and reraise the beams, a parking assist system, a reversing camera and cruise control that brakes itself in emergencies.

Interior equipment includes a powered roof system, climate-control (complete with a stronger Convertible mode), leather trim and Advantage, Sport and Luxury lines to sit beneath the M Sport model.

The Sport and Luxury lines use 17-inch wheels and tyres, which are a size below the standard 18-inch alloys on the M235i.