BMW 4 Series Convertible review
The facelifted BMW 4 Series Convertible has upped its game in terms of driving dynamics but it’s still a great cruiser
BMW gave us the 4 Series back in 2013 and buyers have just about gotten over the shock of having to call the popular 3 Series Coupe and Convertible by another name. If you still aren’t up with the latest naming convention, the 3 Series is now the saloon and Touring estate variant while the 4 Series comes in Coupe, Convertible and Gran Coupe guises. All are now firmly established in the automotive landscape.
It should be no surprise that BMW’s 4 Series models all share the same platform as the latest 3 Series saloon, with an identical wheelbase but a slightly wider track and a lower centre of gravity.
The 4 Series Convertible reviewed here shares most of its bodywork and interior with the 4 Series Coupe, but loses the fixed roof which is replaced by a three-piece folding metal version that tucks away neatly into the boot. The other option in the 4 Series line-up is the Gran Coupe, which is a sleek and stylish five-door/hatchback sister model to the ‘regular’ two door Coupe.
The BMW 4 Series Convertible’s main rivals are the Mercedes C-Class Cabriolet and Audi A5 Cabriolet, both of which have traditional fabric roof which – depending on where you park – may make them feel a little less secure.
Car group tests
You can get the 4 Series Convertible in three trim levels: SE, Sport and the range topping M Sport. For the real power addicts there’s also a full ‘M’ version called the M4 Convertible, which has 431bhp and supercar-threatening acceleration.
A wide range of engines is available in the 4 Series Convertible, with 420d, 430d, and 435d diesel, and 420i, 430i and 440i petrol powertrains on offer. Power outputs range from the 420i’s 182bhp, all the way up to the 440i’s 322bhp. Gear changes are handled by the standard six-speed manual box, but there’s an optional eight-speed auto. You can even get an xDrive version for superior 4x4 road holding, too.
The latest facelift has honed the 4 Series driving experience with tweaks to the suspension and updated the styling with revised LED lights front and rear. There’s also improved tech and classier trim materials in the cabin.
The outwardly sleek and stylish BMW 4 Series Convertible is a weighty beast thanks to the engineering solutions needed to stiffen up its topless body. It’s noticeably less agile and engaging to drive than its Coupe sister car as a result, although it is certainly still fun behind the wheel, especially if open-air motoring is your thing.
There’s a wide choice of petrol and diesel engines offering a range of performance levels – including the impressively efficient 420d. The more powerful engines suit the car’s relaxed nature best, however, and are worth considering, as are the optional auto gearbox and adaptive suspension – if you can cover the hefty price premiums.
The 4 Series Convertible is a practical car to live with too - or it would be if the metal roof didn’t swallow half the boot space when folded. Soft-roofed rivals like the Audi A5 Cabrio will let you take much more luggage on holiday.
Engines, performance and drive
As with the 4 Series Coupe, the 4 Series Convertible sits 10mm lower to the road than a 3 Series saloon. Its centre of gravity is also 20mm lower than that of the 3 Series but the Coupe’s is another 20mm lower still. This manifests itself on the road where, while the Coupe version feels like a sports car the 4 Series Convertible feels a little bit more relaxed, it’s more of a cruiser.
You can also blame the added weight for this: not only does the convertible’s complex folding roof add weight, but so does the extra chassis strengthening BMW has had to fit to the car to compensate for the loss in structural rigidity caused by effectively chopping off the roof.
In the case of the BMW 440i the Convertible is 295kg heavier than the Coupe. This is about the same as driving around with three international rugby players in the car with you at all times. That affects agility compared to the Coupe, which of the two sister cars feels much more like a sports car.
That said the BMW 4 Series Convertible is still a slightly sharper drive than the Audi A5 Cabriolet and Mercedes C-Class Cabriolet. As with the 3 Series on which it’s based, all the 4 Series cars are rear wheel drive – unless you choose the 435d which only comes with the xDrive 4x4 system. If you want the extra grip and all-weather reassurance of all-wheel-drive, you can specify it on the entry-level 420i petrol or any of the other diesels.
Although true performance enthusiasts will always opt for the lighter weight and better agility of the coupe, the 4 Series Convertible’s engine range ensures none of them feel sluggish.
The petrol line-up kicks off with the 2.0-litre 420i with 182bhp, which is enough to see 0-62mph in as little as 8.2 seconds and a top speed of 143mph. The 430i version can get the sprint done in 6.4s but these days it uses that same turbocharged 4-cylinder engine as in the 420i and doesn’t have quite the same sonic accompaniment or throttle response at the BMW straight sixes of old. The 440i – available only in M Sport trim – has a genuine six-cylinder engine that takes the 4 Series into the realms of serious performance, with 0-62mph arriving in 5.4 seconds.
Go for a diesel and the entry level 420d has 188bhp, and beats the 420i to 62mph by a tenth of a second. The 6-cylinder 430d gets you there in 5.9 seconds. The 435d engine is only offered with xDrive, and the extra 4x4 traction means the car is even quicker than the 440i – taking just 5.2 seconds on the benchmark sprint.
As you might imagine, the M4 is the performance king pin with 429bhp and 0-62mph in 4.2s.
MPG, CO2 and Running Costs
The 4 Series costs between £4,000-£6,000 more than the equivalent 4 Series Coupe to buy and the heavier weight means marginally worse performance, as well as poorer fuel economy and CO2 figures.
Overall, the 420d makes the most financial sense. The 420d’s 2.0-litre diesel is capable of 55.4mpg, yet thanks to its 188bhp has enough performance to satisfy most people. It may not sound as nice as the petrol models with the roof down, but this car is more set up for cruising around than being thrashed down a back road. What’s more emissions as low as 133g/km mean minimal tax bills for company car drivers.
Specifying an auto transmission adds just over £1,500 to the price and lowers emissions by 3g/km. It is a worthwhile investment if you can afford it, because BMW manuals don’t have the slickest shift and the pedals are slightly offset. You might also want to improve your car with some other cost options. Items worth considering include the neck warmers, which blow hot air through vents in the front of the head restraint, and the adaptive suspension. The latter improves comfort, plus, at the press of a button you can put the car into sports mode for a more dynamic drive. If you’re not careful though, the tempting options list can make the purchase price rocket upwards.
Thanks to a wide range of performance options, the 4 Series Convertible attracts a wide range of insurance groups too. The most expensive to insure will be the group 42 rated 435d xDrive Luxury auto. The cheapest will be the group 30 rated 420i SE.
The predicted residual values for the 4 Series Convertible are not exceptional. Used car valuation experts CAP suggest all versions are likely to be worth between 36 per cent and 41 per cent of their new price after three years and 30,000 miles. (That’s if you buy at the basic list price, of course – as a rule of thumb you can knock off 50 per cent of the value of any optional extras, too.)
The best performing Convertible according to CAP will be the 420i M Sport with a 41 per cent residual. The worst will be the 420d Sport auto at 36 per cent.
Interior, design and technology
The BMW 4 Series Convertible is a fabulous looking machine roof up or down. Some cars with folding metal tops tend to have bulbous rear ends to accommodate the bulky roof mechanisms. But BMW has managed to engineer its way round this problem by using a three-piece design and complex folding mechanism.
With the roof up the car looks very similar to the Coupe though. That means that it's longer, lower and wider than the 3 Series it replaces, and the rear wheel arches are the widest point of the car.
The latest facelift has delivered a new set of LED light clusters front and rear plus a large air intake sweeping across the front of the car that’s said to give it a visually wider and sportier stance.
You can get the car in three trim levels: SE, Sport and the range topping M Sport, which is marked out by more aggressive bumpers, side skirts and detailing, and comes with the excellent adaptive dampers as standard.
Inside, the layout will be familiar to anyone who’s driven a 3 Series, with the same combination of an upmarket feel and a simple and smart layout. BMW added more chrome detailing and other enhanced materials. There are slender buttons for the air-con and audio system, as well as the excellent central infotainment screen, while the 4 Series also benefits from BMW’s revised touchpad iDrive controller which alloys you to write letters into the satellite navigation using your finger.
As you’d expect, fit and finish are first rate, with quality materials used throughout, while the low driving position enhances makes the car feel very sporty to sit in. Standard equipment includes Bluetooth, a DAB radio, cruise control and leather seats, which are heated in the front – a welcome addition in a drop top.
Sat-nav, stereo and infotainment
There 4 Series has options galore, one of which is the £1,990 Professional Media Pack with navigation that’s standard on M Sport cars. This may seem expensive but the huge screen has a fabulous display while the live traffic updates will help you avoid traffic jams. The latest update sees it gain a new tile-based menu screen that can be adapted by the individual user. It also gives you the full range of BMW ConnectedDrive services.
A head-up display is also on the 4 Series options list as is the Digital Cockpit display with its TFT screen in place of the instrument cluster and numerous display options that adjust according to the driving mode selected. BMW also offers an inductive charging tray to wirelessly charge your smartphone.
Practicality, comfort and boot space
In the front, the 4-Series Convertible is just like the Coupe. So there’s plenty of adjustment in the drivers seat, a well laid out dash and large practical door bins. You sit low thanks to the sporty driving position, but visibility is good. The folding metal roof means that refinement is extremely good for a Convertible – at least when it's raised – and it adds to security too, if you’re the type of person who leaves stuff lying around on the back seat.
If you want to take advantage of bright winter days here in the UK, then the BMW Air Collar is a worthwhile option. It warms your neck with a blast of hot air – but a woolly scarf will be cheaper.
The BMW 4 Series Convertible measures 4,638mm long, 1,825mm wide and 1,384mm tall. That compares to the Audi A5 Cabriolet at 4,626mm x 1,854mm x 1,383mm and the Mercedes C-Class Cabriolet at 4,686mm x 1,810mm x 1,409mm.
Leg room, head room & passenger space
The back seats are positioned more upright than the seats in the coupe, which is one of the compromises needed to make room for the folding roof mechanism when it’s stowed. This means the seats don’t feel so comfy over long distances, and it also affects the headroom – people over six feet tall will definitely struggle if they’re relegated to the back. It’s a great place for kids though, and there are standard-fit Isofix seat anchors as you’d expect.
The boot on the 4 Series Convertible is a decent 370 litres when you’ve got the roof up. Actually that’s pretty impressive, but the trouble starts when you want to travel al fresco, as lowering the top immediately slashes the available luggage space to just 220 litres.
It’s a significant issue if you want to use your Convertible for touring, particularly when you consider that the Audi A5 Cabriolet has a very respectable 380 litres of boot space with its roof dropped.
Reliability and Safety
The BMW 4 Series uses many of the same mechanical and electronic components as the current 3 Series, so you can buy the Convertible and Coupe models safe in the knowledge that they should be trouble-free.
To prove the point, the BMW 4 Series did very well in our 2017 Driver Power satisfaction survey. It came 9th overall in the manufacturers section, with owners praising its engines and gearboxes in particular. Running costs were said to be less of a highlight. The BMW 4 Series itself came 22nd over all in the cars survey, a fine showing.
Euro NCAP hasn’t performed an independent crash test on any of the BMW 4 Series models as yet, but it did crash its 3 Series sister car when it was new back in 2012. The BMW saloon did extremely well, scoring 95 per cent for adult occupant safety, 84 per cent for child occupant safety, 78 per cent for pedestrian safety and 86 per cent for safety assistance systems.
As you’d expect, you can pack your 4 Series Convertible with extra safety kit, including lane departure warning, a reversing camera, a head-up display and active cruise control.
BMW offers a three-year unlimited mileage warranty and 36 months’ roadside assistance. Audi and Mercedes offer similar cover.
Adding to the financial appeal – and making it easy for BMW owners to budget for maintenance – is a fixed-price servicing package, which provides five years or 50,000 miles of servicing cover from around £500.