(Pocket-lint) - We already know the BMW 435i well, having driven one back from its launch event in Scotland last summer and then having spent a week with it, driving it around the UK.
But what happens if you lop the roof off a 4-Series? You get a 4-Series Convertible, obviously. And we love our convertibles in the UK - in fact, per head of population we buy more of them than any country in Europe. Which is a bit nuts, given how we like to moan about the weather. Another example of our famous gallows humour?
Always take the weather with you
Any way you cut it, the UK is a fine test of a convertible. You need to be able to get the roof up and down quickly to take advantage of those gaps between rain showers.
Heated seats and wind deflectors should almost be mandatory in order to ward off the worst of our chilly Spring seasons. And you're going to need the thing to be watertight, refined and do a good impression of a coupe for all that time you're going to spend with the roof up.
At which point we feel it's only fair we fess up and say that we went to southern Spain to drive the new 4-Series Convertible and - you know what we're going to say - it didn't rain once. But that's exactly the glory of a convertible, so down the roof came and we soaked up those rays.
So let's get the obvious - and the good - out of the way first. There can be few better places to spend time than in a brand new BMW with the rood down, on a beautiful road and with the sun beating down on your head.
And be that experience in the South of Spain or Skegness, the 4-Series Convertible performs pretty impeccably with its roof down. There's almost no wind buffeting thanks to the (standard) deflector. And with the side windows rolled up, the carremains refined, the cabin warm and conversation possible at entirely non-shouty volumes up to and above motorway speeds.
Breathing down your neck
The experience is augmented by BMW's new Air-collar - a neck-level air-warmer system, which rather like Mercedes' 'Air Scarf' gently blows warm air round the back of your neck and shoulders from a vent at the base of the headrest/top of the seat.
If that description makes the experience sound just a bit seedy then fear not because, as those who drive convertibles regularly will know, this is exactly the part of your body which really feels the draft and forces should you to put the roof up and aren't wearing suitable attire. We've always felt Merc's system working, but we could barely detect the BMW's, which has an auto-adjustment function dependent on driving speed and other variables. Which is nice, because you stay warm without feeling like someone is - literally - breathing down your neck.
The hills are alive to the sound of… a straight six
The other bonus of specifying your 4-Series with a roof that comes off (assuming it's badged 435i) is that you get to hear the sonorous note of that straight-six petrol engine. BMW's got a long, prestigious history of engines in this formation and - as a rule - they sound great. But when we drove the coupe, we couldn't help feel that they'd muted the thing just a little too much. In the convertible, with the roof down it's obviously more audible and there's a nice little burble tuned into the exhaust which doesn't exactly intrude but - when pressing on - you definitely know is there.
We know that the reality is most people will buy the 420D model rather than this 435i petrol though. We did briefly sample that car and found that it still felt decently swift. Although the diesel installation seemed much more refined than in the new 2-Series coupe, it's still ultimately a diesel and could never be mistaken for anything else when the top's down. Yes, it will do 20mpg more than the 435i, but if we were buying one of these cars and didn't have company car tax to worry about then we'd be keener on one of the small petrol engines. It's just a nicer aural experience and more refined with the roof down.
Unfortunately adding a folding metal roof to this car adds quite a bit of weight over and above the coupe. So by taking away you're actually adding weight.
It's a folding hard top unit, rather than the traditional fabric hood. That means when it's up car feels just like a coupe. Nice. But still, roughly 200kgs of weight penalty just to be able to put the roof away is quite a shocking amount in the context of something weighing 1,500kg to start with. And even with 306 horsepower driving the rear wheels, the 435i Convertible really feels its extra weight, particularly after you've driven the coupe.
READ: BMW 435i M Sport review
It's all relative of course. So much horsepower, and a car that can crack the 60 miles per hour dash in a time that starts with a five could never be described as slow. We just feel it's worth pointing out the difference in comparison to other models with this engine.
But if you're buying a 4-Series convertible, such thoughts are probably far from your mind, as you'll be more interested in boulevard cruising than B-road bashing - and this car is absolutely great at the former.
Beyond that slight strain of the engine, the 435i Convertible does a pretty fine job on more challenging roads too, especially for something missing a roof. Standout points include how well BMW has got these cars riding on 19-inch run flat tyres, especially when they - like our test car - are fitted with the adaptive suspension system, which we think might be a must for the UK's pock-marked roads.
You'll want your convertible to be "liveable" too, and it's perhaps unsurprising that BMW has worked hard here: you'll get four people's luggage in the boot for a week away if the roof's up. And if you've got the roof folded then BMW's included a rather complex function, which at the simple press of a button makes the whole boot structure, including the stowed roof and glass too, hoist itself up and out of the way. That leaves a big slot through which to post your luggage into the boot.
The joy of specs
In the 435i Convertible you also get an interior which is the same as any other 4-Series. That means it's ergonomically infallible but lacking the utter wow factor of, say, a new Mercedes C-Class.
As ever, we'd urge you to find the extra money to upgrade to the Pro Navigation system, which includes the bigger display screen and highly useful 'RTTI' real-time traffic information system. Despite it being mounted high on the dashboard and lacking a hood/cowl, even in the bright sunlight of Spain it managed to remain entirely readable 99 per cent of the time.
Other spec thoughts: if you fancy connecting more than one phone at a time or streaming music then you'll need the 'enhanced Bluetooth' option at between £300-£450 (dependent on which model you start with in the first place). But otherwise, it's a good job that BMW has included most things you'll want as standard - such as heated seats and xenon headlamps - which you have to pay extra for on its sister car, the 3-Series.
It's a credit to BMW's engineers that chopping the roof off the 4-Series has dented its core qualities very little. We could argue that between Coupe and Convertible, the latter is the one to buy. Being able to fold the roof brings an entirely new dimension to the experience of driving this car and loses very little in insulative qualities when the roof is up. It does add to the weight, though, which can be felt.
Ultimately, people choose these types of car on image, and have their own views on what the coupe "says" about them versus the convertible. In this case, we would still take the coupe as we can't help feeling sad about that weight penalty and how it can be felt in certain situations when you're driving the car.
In the end, especially when considered in the soft sunlight on the side of a mountain in Southern Spain, the 4-Series Convertible is a lovely car and polevaults it way immediately to the top of the convertible class. We're sure that the work BMW has put in means it'll be rather good in the UK too - even on the 300 days a year that it's raining.
If a four-seater convertible is you thing, and if having a convertible but getting as close as possible to a coupe feel when the roof is up is what you're looking for, this the 435i is as good as it gets. The automotive equivalent of having your cake and eating it, you might say. Roll on the summer.