BMW 428i convertible 2014 review

There's no need to wait for the latest Transformers movie, just pull up a chair and watch the new 4 Series switch from coupe to convertible.

The folding of the steel lid takes just 20 seconds and the transformation is a thing of beauty. It is a simple experience for the owner, yet the mechanics are extremely complicated. Once the lid has retracted into the boot, you can press another button and the folded metal panels, now stacked together, rise up 40cm, allowing you to feed in a long item, maybe a surfboard or perhaps a jousting stick, before it drops back down.

The 4 Series frame has also been revised to allow the rear seats to fold down, opening up more cargo room. Some customers may never use this feature, but the advanced technology shows how far car companies go to improve the ownership experience and, in this case, make convertibles easier to live with. This is an easy car to like, unless you expect it to deliver hard sports car thrills.

The 4 Series title is part of BMW's new naming structure, in which the 3 Series coupe and 3 Series convertible have become 4 Series cars and the 1 Series coupe and convertible are now 2 Series cars (confusingly so too is the new front-drive 2 Series Active Touring hatch).

So, this is just a new generation of 3 Series convertible. Like that car, it has four seats and a steel-folding roof. There is ample legroom and headroom for all four passengers with the roof in place, a welcome trait when a sunny cruise down the coast is rained out.

PRICE / RANGE

The 4 Series convertible is available with three engines, comprising entry-level diesel, four-cylinder petrol and six-cylinder petrol. Pricing starts at $88,000 for the 430d diesel, rises to $97,500 for the 428i petrol. The 435i tops out at $126,600.

Carsguide didn't spend any time in the 2.0-litre diesel (135kW/380Nm), so we can't judge, although it is possible to note that the sound of diesel engines usually clashes with the idea of traditional open top motoring. The 428i uses a 2.0-litre four-cylinder petrol engine with a single twin scroll turbocharger. It is good for 180kW and 350Nm.

That sounds like lots for a compact car, but it must be noted that the extra body protection to keep the 4 Series convertible stiff enough without a roof in place, as well as all the extra motors to fold it away, adds a hefty 225kg, which means the car ends up weighing around 1700kg.

DRIVING

It is no slug, the engine delivering maximum pulling power from 1250rpm through to 4800rpm, but it's no slingshot either. There's sufficient power for a fun country drive.  The exhaust note is subtle yet sporty, although you only really hear it when the roof is down.

ZF's eight-speed automatic is standard, changing gears smoothly and quietly via the stick shifter or paddles. A 435i is powered by a turbocharged 3.0-litre petrol six (225kW/400Nm). The improved performance is handy but most people will be happy with the lesser model, given these will be used for city driving and the odd cruise.

As a pay off for all the extra weight, the body stiffening means the 4 Series does not suffer the kind of body wobble that can ruin a convertible drive experience (as in Audi's A5) and the ride is comfortable. The 428i handles well enough, but starts to struggle with the extra bulk when you begin to push hard. The steering, something BMW used to do brilliantly, is vague.

The 428i is reasonably well specified and gets many of the features you'd expect at this price including leather seats with heater function, 19-inch wheels, satnav,  big hi-res centre screen and adaptive sports suspension.  The 435i comes standard with keyless entry and start and Air Collar, which feeds hot air on to your neck.

The options list includes advanced technology that is available on some vehicles less than half the price. Self-parking is $675, head-up display is $1700, digital radio tuner is $500 and lane departure warning is $1000, so it's up to owners to decide what features are worth the money.