We try out the open-top version of BMW's new 4 Series.

BMW launched its new range of 4 Series Coupés onto the UK market in late 2013, with the Convertible version being introduced earlier this year, and in doing so the company has now completely replaced its long-running line of 2-door 3 Series Coupés and Convertibles. 

As you may already know, the 4 Series is lower, longer, wider and has sleeker styling than its 3 Series predecessor, but BMW has also implemented changes to the chassis, suspension and braking systems, and added some creature comforts to further improve the driving and ownership experience.

Believe it or not there are currently no less than 42 different 4 Series Convertible variants on sale, and they range from the £34,210 420i SE manual to the £63,375 M4 auto, so my test car - a 428i auto in Luxury spec which without any optional extras sells for £39,515 OTR, is at the more affordable end of the range.

As you may also have previously gathered, in BMW-speak the name 428i no longer indicates that there's a 2.8-litre (6-cyl) lump under the bonnet. 428i now means a 4-cyl 1,997cc TwinPower Turbo petrol that makes 254hp from 5,000 to 6,500rpm along with 350Nm of torque from 1,250-4,800rpm.

This coupled with the 428i's 8-speed auto/paddle-shift transmission means that the car is an eager performer with keen off-the-line acceleration and more than ample grunt for overtaking. And although as just mentioned it's a 4-cyl engine, it sounds more like a throaty six, and that's an audio experience best appreciated with the roof down.

Indistinguishable From The Fixed-Roof Coupé In Terms Of Interior Noise

Despite this model's keen performance, its claimed acceleration figure - 0-62mph in 6.2 secs - is a little behind the 5.8 secs of an equivalent 428i fixed-head Coupé. The Convertible's 42.8mpg combined and 154g/km of CO2 are also very slightly inferior to the 428i Coupé's figures, but with the sun beaming down and a cool breeze in your hair you won't be bothered, and there are perfectly good reasons why this should be so, which I'll come to in a mo'.

In common with the more recent 3 Series Convertibles, the 4 Series drop-top has a 3-piece retractable metal roof which at the touch of a button can now be lowered in 20 seconds while driving at 8mph or less. Aided by a new sound-absorbing roof headlining, which apparently cuts wind noise by 2 decibels, the Convertible with roof up is essentially indistinguishable from the fixed-roof Coupé in terms of interior noise and ambience, which is to say it's all suitably quiet and civilised inside.

Boot capacity is necessarily sacrificed on most contemporary convertibles, especially those with folding hard-tops, but in this respect BMW has gone beyond the call of duty on the 4 Series. With the roof up there's 370 litres of loadspace (20 more than the old 3 Series Conv.), and with the roof lowered that's reduced to 220 litres. The 4 Series' boot also has wider access and there's an innovative electro-hydraulic loading system that's every bit as intricate and complex as the roof mechanism which maximises the available space. 

The new 4 Convertible also differs from its Coupé sibling in a number of more subtle ways. In addition to improved pop-up roll-over bars, the standard Dakota leather upholstery has 'Sun Reflective Technology', the suspension has been re-tuned and the body stiffened. I looked hard for any sign of scuttle shake, and on rougher roads also felt for any movement, but none was evident.

Steering Is Benchmark Good And There's Really No Shortage Of Grip

Unsurprisingly, the Convertible's body stiffening, powered metal roof and other mechanisms all add weight, so at 1,775kgs the 428i Convertible Luxury with Sport auto transmission is some 230kgs heavier than the equivalent Coupé model, hence the reason for its slightly inferior 0-60, mpg and CO2 figs, although all 428i variants have a 155mph top speed, Convertible included. 

My test car was loaded with no less than 17 optional extras, including £750 Adaptive M Sport suspension, £610 19-inch alloys and the £250 variable sport steering option, so I'm not in a position to comment on how a base spec example might drive, but with that £1,570-worth it handles with great composure, it rides very comfortably, its steering is benchmark good and there's really no shortage of grip. The £1,690 Sport auto transmission adds to the experience by shifting through its eight ratios almost imperceptibly.

Although £825 for the head-up display might seem like an extravagance on top of the £1,000 BMW Professional infotainment package, it makes following the satnav's visual guidance far easier in bright sunlight, so that's definitely worth considering on any BMW Convertible... 

With all this and more my 428i Convertible's retail price was £48,675 OTR. That's no small sum, but if you spend it on one of these then you have my blessing.