BMW 4 Series Convertible review

We love a bit of innovation, but sometimes traditional methods are best – as demonstrated by the BMW 4 Series Convertible.

You see, after switching to a folding metal roof for the previous-generation car, the convertible variant of the BMW 4 Series has now returned to a good old-fashioned fabric one. Why? Well, for starters, a soft-top takes up far less space. You could fit your luggage or the roof in the boot of the previous model, but not both at the same time. The revised design fixes that.

What's more, for most car buyers, good fuel economy and low emissions are more important than ever, so it's no surprise that the option of saving weight by using canvas rather than steel up top was impossible to ignore.

That said, this latest 4 Series Convertible has put on a few pounds because it's longer, wider and stuffed with more equipment, but the new roof at least keeps the increase to a minimum. The model has also gained mild hybrid technology, which means there's a battery-powered electric motor assisting the engine, potentially improving efficiency and performance.

The engine line-up mirrors the rest of the 4 Series range. It starts with a 2.0-litre turbocharged petrol with a choice of two power outputs, plus there's a 2.0-litre diesel for the lowest running costs. A slinky BMW wouldn’t be complete without the option of some six-cylinder goodness, though, so you can also have a couple of 3.0-litre diesels or a potent 3.0-litre turbocharged petrol.

Rival convertibles have thinned out considerably, with only the Mercedes E-Class Cabriolet offering four seats. If you don’t need four seats, there are sportier cars such as the BMW Z4, Jaguar F-Type Convertible and Porsche Boxster to consider.

So, how does the BMW 4 Series Convertible compare with the best cabriolets out there? We'll let you know over the next few pages of this review. We'll also tell you what the performance is like, how swanky it is inside, how practical it is and how steep or otherwise the running costs are.

Once you've picked your next car, we can help you get it for the lowest price if you search for your chosen make and model on our free What Car? New Car Deals pages. They can help you find some mouthwatering new convertible car deals.

The 4 Series Convertible range kicks off with the 420i model, which uses a 2.0-litre turbocharged petrol engine producing 181bhp. It’s our pick in the BMW 4 Series Coupé and remains so here, because it should be brisk enough for most people and makes sense financially.

The convertible variant has to lug around 165kg more than the coupé, so the engine does have a harder time of it here. It takes a not particularly sporty 8.2sec to accelerate from 0-62mph and feels quite flat low down, so it's just as well that it's happy to rev. If you upgrade to the 430i – also a 2.0-litre petrol, but with 241bhp – the performance does live up to the racy looks. It’s effortless at low speeds and the 0-62mph time is a brisk 6.4sec.

For the best performance, there’s the 335bhp M440d diesel or the 369bhp M440i petrol: both send their power to all four wheels and deliver whipcrack acceleration (0-62mph takes just 5.0sec in the diesel and 4.9sec in the petrol). If you’re planning on covering big distances, then the diesel with its tidal surge of accessible torque makes for an effortless motorway cruiser, but if you prefer to spend your time on demanding country roads then the petrol is freer revving and makes a more soulful noise.

Whichever engine you choose, you get an automatic gearbox that makes slick changes, especially in Sport mode. You can take control yourself using the shift paddles mounted on the steering wheel.

Lopping the roof off a car often makes its structure rather floppy, but the 4 Series Convertible is better than direct rivals in this respect. You’ll see the rear-view mirror wobbling sometimes, but it takes a big bump for any shake to come up through the steering column. That stiffness is good news for handling, because it means the steering remains terrifically precise, allowing you to place the nose of the car exactly where you want it.

If you go for the M Sport Pro Package or one of the M440 engines, BMW gives you M Adaptive Suspension. It lets you stiffen or soften things by selecting different modes, and even Comfort mode does an excellent job of propping up the body during hard cornering. In fact, on pockmarked and uneven B-roads, Comfort is a better bet than the more focused Sport setting because its extra suppleness stops you from being bounced off course.

Whichever mode you select, the car has an agility that's surprising given its extra weight compared with the coupé, and a comfortable ride, even with big 19in wheels fitted. It rounds off all but the nastiest bumps and potholes, and deals with undulating tarmac with a great balance of comfort and control, making this a car you’d happily cruise around in all day. We’ve yet to try the standard suspension set-up but we’ll update this review when we do.

When it's in place, the fabric roof does an excellent job of keeping noise down, with only a bit of wind whistling from around the front windows. There's a fair amount of road noise filtering up through the floor, but the engines settle down when you’re not pushing on.

If you drop the roof but keep the windows up, you won’t arrive at your destination looking like your hair has had a close encounter with a hurricane. You can add an optional Warm Air Collar (as part of the Comfort Pack) – basically, vents in the front seats that blow warm air onto your neck. The removable wind deflector, which can be fitted over the rear seats, is worth considering to protect your hairdo.

When you're inside the 4 Series Convertible, you’d be forgiven for thinking you’d accidentally got into a BMW 3 Series. The driving position, for example, is almost identical, as are the dashboard and infotainment system.

In many ways, that's great news, because it means you get a comfortable and supportive driver’s seat with lots of adjustment, as long as you add optional adjustable lumbar support.

Forward visibility is good, with windscreen pillars that are slim enough not to get in the way at junctions. Rear visibility isn’t great with the roof up because the rear headrests block much of the small rear screen, and there’s a lot of canvas obstructing your rear three-quarter view. Helpfully, front and rear parking sensors, plus a rear-view camera are standard on all models.

Likewise, all 4 Series have bright adaptive LED headlights for safe driving at night, maintaining maximum illumination without blinding road users ahead of you. Laserlight matrix headlights are optional, and (as their name suggests) use laser technology for even brighter illumination.

Build quality is first rate, with only the odd bit of hard plastic and some silver-painted buttons on the dashboard letting the side down a little. 

The infotainment system is truly brilliant, though. All versions get a 10.3in display that you can either use as a touchscreen or operate by twisting and pressing a rotary controller between the front seats. We think it's much less distracting while you’re driving than a touchscreen-only infotainment system.

All trims come with Android Auto and Apple CarPlay smartphone mirroring, along with a DAB radio and built-in sat-nav. Wireless phone-charging is available as part of the Technology packs, which also include a gimmicky gesture-control function for the infotainment system.

The optional 464W, 16-speaker Harman Kardon sound system (available in Technology and Technology Plus packs, or as a standalone option) sounds epic.

No one buys a two-door soft-top like the BMW 4 Series Convertible for its space and practicality, but the chances are you occasionally need four seats and a boot that can swallow more than just a squishy bag. If that’s not the case, you might want to consider a thoroughbred sports car (the Porsche Boxster for example).

The 4 Series is as spacious as a BMW 3 Series in the front, so you’re unlikely to have any problems with head or leg room. Storage space is impressive, too, with a big glovebox and a decent cubby under the centre armrest.

There's a useful lidded storage area in front of the gear selector, where you’ll find a couple of generous cupholders and a space for your phone and keys. You also get partitioned door bins so loose items don't roll around.

Getting into the rear seats involves squeezing through a relatively narrow gap, but the same is true of all four-seat convertibles. Once you’re in, you’ll find acceptable leg room

Taller adults will need to cower slightly or put up with their head resting on the ceiling, but a couple of six-footers will be comfortable enough in the back as long as the journey isn’t too long. BMW gives you a couple of cupholders back there, too, but the other storage areas are pathetically small.

The boot is slightly smaller than in the BMW 4 Series Coupé and – as with most convertibles – offers more space with the roof up than with it down.

You can fold down the rear backrest using a handy lever in the boot. The seats don't split into sections for greater flexibility, but there is a cubby behind them where you can store the optional wind deflector vertically. The boot is a little longer, taller and wide than the one in the A5 Convertible, but they have space for the same number of carry-on suitcases – six.

The BMW 4 Series Convertible is a bit of a bargain compared with its closest four-seat rival – the Mercedes E-Class Cabriolet – and you should be able to can get a healthy discount through our New Car Deals service. The Mini Convertible and VW T-Roc Cabriolet are cheaper still, but also smaller.

If you’re a company car driver, the 420d diesel will cost you the least in monthly salary sacrifices and should return the most miles to the gallon. The 420i petrol is a cheaper option if you're buying with cash or on PCP finance, and is predicted to hold on to its value better. Indeed, the model as a whole is predicted to hold its value against depreciation better than rival convertibles.

The range kicks off with M Sport trim, which comes with plenty of standard kit, including 18in alloy wheels, leather seats (heated in the front), cruise control and three-zone climate control. We’d recommend forking out extra for adjustable lumbar support and the M Sport Pro Package, which adds adaptive suspension.

You could be tempted to upgrade to the M Sport Pro Edition model, because that includes the adaptive suspension as standard, along with 19in alloys and a choice of three exclusive colours, but we don’t think it's worth the extra cost. The range-topping M440i is similarly equipped to the M Sport Pro Edition, but gets the mighty six-cylinder turbocharged petrol engine under the bonnet.

The 4 Series Convertible didn't feature in the 2022 What Car? Reliability Survey, but BMW as a brand finished in 16th place (out of 32 brands), above every premium rival except Lexus (in first place).

The BMW 4 Series was tested for safety by Euro NCAP in 2019, and both the Coupé and Convertible versions received the full five-star rating. They scored well, partly thanks to the model's standard collision-prevention equipment, including automatic emergency braking (AEB) and lane-departure warning.

Buyers can also add the optional Driving Assistant Professional Pack, which comes as part of the Technology Plus Pack. That includes adaptive cruise control, a more advanced lane-keeping assistance system, a front cross-traffic alert system and automatic speed-limit assistance.

For all the latest reviews, advice and new car deals, sign up to the What Car? newsletter here