BMW 8 Series Convertible review

Cars like the BMW 8 Series Convertible provide a real tonic for the soul. With one on your drive, the prospect of getting away from it all is literally on the doorstep: just grab the keys, drop the top and hit the road for somewhere with bluer skies and greener grass.

At the heart of the 8 Series Convertible is a platform that combines high-strength steel, aluminium, magnesium and carbon-fibre-reinforced plastic, all with the aim of keeping weight down but structural stiffness high. Not that this is a sports car – although BMW likes to call itself the Ultimate Driving Machine manufacturer, the 8 Series has a large footprint.

That moves it away from sports models such as the Porsche 911 Cabriolet towards the luxury end of the market, where you’ll find the Bentley Continental GTC and Mercedes AMG SL.

As with its tin-topped sibling the BMW 8 Series, it's available with a six-cylinder petrol engine that sends its power to the rear wheels, or a thumping great V8 that powers all four wheels. The V8 in particular is prodigiously quick.

Read on as we rate the BMW 8 Series Convertible in all the important areas and tell you how it compares with rival drop-tops you might be considering...

Eagle-eyed petrolheads might have noticed that the BMW 850i Convertible has the same petrol engine as the previous-generation BMW M5. And they might also have spotted that it doesn’t have quite as much power. In effect, the engine has been detuned, but that shouldn’t necessarily come as a disappointment.

The 4.4-litre twin-turbo V8 still feels immensely flexible and impressively refined in a way that entirely befits an open-topped grand tourer. It’s smooth and relatively quick to respond to accelerator inputs, with only a short delay between pressing the pedal and feeling the turbos spin up and blasting you down the road.

Not only is it effortless to drive, but with the added traction of xDrive four-wheel drive you can also deploy all 523bhp with virtually no drama when the road opens up.

We haven't yet driven the entry-level petrol 840i, which has rear-wheel drive rather than four-wheel drive, but objectively, the M850i is the engine to go for. (If you want an even more powerful version, see our BMW M8 review.)

We’ve no complaints about the model's cruising manners. With the roof up, there's a bit of road noise and some faint wind whistle at 70mph, but it’s nearly as refined as the hardtop BMW 8 Series. And while it doesn’t quite deliver the stately progress of the significantly more expensive Bentley Continental GTC it does produce much less wind and road noise than the Mercedes-AMG SL.

With the top down, the wind deflector does a great job at keeping your hair in place, and it’s possible to hold a conversation, even at motorway speeds. Just as impressive is the car’s rigidity. It takes a very rough surface to get the body flexing, and even then, you’ll only ever see the slightest tremors in the rear-view mirror. That’s not the case in the Continental GTC – potholes and raised metalwork cause their bodies to shudder noticeably.

The 8 Series is quite firm for a luxury convertible so it's not as supple over speed bumps as a Continental GT and fails to waft as well as them on motorways.

With four-wheel steering, a clever traction-boosting "eDiff" on the rear axle (standard on the M850i) and the optional M Adaptive anti-roll bars fitted to our test car, it feels much nimbler than it looks. Granted, the steering doesn’t tell you a great deal about what’s happening between the tyres and the road, but you can still make quick progress with plenty of grip. 

It’s certainly more fun for keen drivers than a Continental GTC – although those looking for proper sports car thrills should look at the Porsche 911 Cabriolet.

After you’ve absorbed the sleek exterior of the BMW 8 Series Convertible, with its flowing profile and taut surfaces, you might expect the interior to be equally dramatic.

Instead, you’ll find an agreeable interior that feels like a plusher BMW 5 Series. In terms of visual panache it falls some way behind the Bentley Continental GTC and Mercedes-AMG SL

That said, BMW has always focused on restrained visual designs, preferring outright build quality to showiness. It’s here that the 8 Series Convertible scores highly, and from the precise stitching on its leather dashboard to the numerous brushed chrome trim pieces, everything looks and feels well honed and tactile.

There's good news when it comes to the infotainment system too: BMW’s latest-generation iDrive, with a 12.3in touchscreen, is the best on the market. It's responsive, mostly intuitive and one of the easiest systems to operate on the move, thanks to a rotary controller that supplements the touchscreen. Android Auto and Apple CarPlay come as standard.

Another 12.3in digital screen for the driver's display is standard across the range, showing maps and media where they're easy to see. Plus, you get a head-up display that projects your speed on to the windscreen.

You feel quite submerged in the 8 Series Convertible, thanks to its low seating position and high window line. The seats are comfortable and there's lots of adjustment to allow you to get comfortable, but it can be tricky to see out in all directions.

Don't worry, though: you get front and rear parking sensors, a rear-view camera and, for night-time driving, LED headlights as standard (Laserlights are available as an option).

There’s loads of space in the front of the BMW 8 Series Convertible, with plenty of head and leg room for a couple of tall adults, and enough width for occupants to sprawl out.

However, there’s very little leg room in the rear. In fact, we’d go so far as to say that the rear seats are better suited to a couple of weekend bags than they are to humans.

The 8 Series Convertible's boot space is reasonably big, with 350 litres of storage – more than a Bentley Continental GTC or Mercedes-AMG SL. You'll fit in a few small suitcases but it's too shallow for anything bulky.

The BMW 8 Series Convertible sits at the premium end of the convertible car market, so it's not cheap, but it's not bad value relative to its rivals. Even the top-end M850i, for example, is significantly cheaper than the equivalent Mercedes-AMG SL and Bentley Continental GTC while the 840i massively undercuts the Porsche 911 Cabriolet.

You won’t need to add many options but you can go to town adding extras if you want to. All models have two-zone climate control, leather seats, power-folding door mirrors and heated seats. You can also add heated armrests, a heated steering wheel and much more.

The M850i adds a sports exhaust system, lightweight 20in wheels and the M Sport differential for added cornering traction. All models get a wind deflector and BMW’s Air Collars, which are integrated into the front head restraints and provide a stream of heated air to warm your neck when the roof is down.

In terms of efficiency, the 840i is reasonably frugal: at a cruise you can expect around 35mpg. That’s far more palatable than the mid 20s you’ll experience in the M850i (and even less in the BMW M8 Convertible).

The BMW 8 Series hasn’t been crash-tested by Euro NCAP but it has a broad suite of active safety aids, such as automatic emergency braking (AEB), lane-keeping assistance and blind-spot warning, to help keep you safe.

The 8 Series Convertible wasn’t included in our 2024 What Car? Reliability Survey but BMW as a brand finished eighth out of the 31 manufacturers ranked. That puts it above Porsche and Mercedes (Bentley didn't feature). BMW gives you a three-year, unlimited-mileage warranty.

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