Test Car Specifications
Model tested: BMW M850i xDrive Convertible
Pricing: £107,100 as tested; starts at £83,295
Engine: 4.4-litre twin-turbocharged V8 petrol
Transmission: eight-speed automatic, four-wheel drive
Body style: two-door, four-seat convertible
CO2 emissions: 229g/km (VED Band 226-255: £1,815 in year one)
Combined economy: 28.5mpg
Top speed: 155mph
0-62mph: 3.9 seconds
Power: 530hp at 5,500-6,000rpm
Torque: 750Nm at 1,800-4,600rpm
Boot space: 350 litres with roof up
What's this?
The BMW 8 Series Convertible is the second body style to be launched in the new range, following on from the accomplished 8 Series Coupe (and preceding the 8 Series Gran Coupe). The Convertible seats four, as in the Coupe (though the back seats are even more cramped, so best to use them for luggage), and there's a multi-layer folding soft-top. This fabric item folds away smoothly in 15 seconds at speeds of up to 31mph and can be had in a choice of black or black with silver flecks through it.
Naturally, the need to accommodate the folded roof (without resulting in an ugly big carbuncle on the back of the car), means practicality compromises. So, along with smaller rear seats (with more upright seat backs), the boot shrinks 70 litres to 350 litres. Though that's only possible with the roof in the up position. To drop the top, a rather unsatisfactory flap in the boot must be in place, further reducing its capacity. Still, we don't expect the target audience to prioritise luggage space. Saying that, one of BMW's people did say that it's important that cars such as the 8 Series Convertible can take two sets of golf clubs (stereotypes are alive and kicking) and, to manage that feat, its rear seat back splits and folds 50:50.
The front part of the cabin is almost identical to that of the 8 Series Coupe, including the snazzy-looking two-screen dashboard and high-quality materials throughout. There are lush leather-covered seats here, featuring sun-reflecting technology and air-warming vents in the headrests with three different settings. Keen roof-droppers should pay a little more to get the heating pack that warms the steering wheel, the door armrests and even the soft leather atop the centre console.
At the time of writing, there are just two variants of the 8 Series Convertible to choose from. The 840d xDrive M Sport Convertible is £83,295 and powered by BMW's gravelly turbocharged 3.0-litre straight-six diesel. It makes 320hp and, more importantly, 680Nm of torque from just 1,750rpm, allowing it hit 62mph from rest in 5.2 seconds, yet it can return nearly 40mpg. It gets an eight-speed automatic and xDrive four-wheel drive.
Here, we're testing the range-topper (for now, as an M8 Convertible is in the pipeline), the M850i xDrive Convertible. As in the Coupe, it gets a rather feisty twin-turbocharged 4.4-litre V8 petrol engine up front, the eight-speed automatic transmission and an electronically controlled rear differential to enhance the xDrive four-wheel-drive system. It costs £107,100.
How does it drive?
Now, if we're to stay true to the stereotypes, this is where we say that it doesn't really matter how well the 8 Series Convertible drives, but thankfully, BMW doesn't think that way. So yes, the open-topped version of the 8 Series is heavier (by about 120kg) than the Coupe equivalent and it's 'a few per cent' less stiff in torsion, too, but nobody normal is going to notice those differences on the public road.
With an 'M' in its model name, the M850i is naturally tipped toward the sporting end of the automotive spectrum, so don't choose this model if comfortable long-distance cruising is your thing. It's not at all bad in that setting (and wind noise from the soft roof is commendably low), but the wide tyres and relatively firm suspension make it clear that this car has a chassis that's designed to be tested. Nonetheless, adaptive damping helps the M850i widen its breadth of capability, further assisted by the usual array of driving modes.
Leave everything in their default settings and this car starts up with a suggestive rumble from its big exhausts, but the V8 up front is muted for the most part, unless you demand all of its performance with the accelerator. The M850i is pleasant to amble around in in this guise without unduly taxing the driver, thanks to increased power steering assistance and smooth gear changes.
The next step up is Sport, and this is probably the M850i at its best. Gearchanges are snappier, the throttle response and engine sound are notably sportier and the suspension firms up. You can make rapid progress with very little effort and a lot of enjoyment in this setting. The body control is good, there's a huge amount of grip from the wide tyres and the 8 Series does a good impression of a very sporty car indeed.
But that wasn't enough for BMW's engineers. Oh no. Perhaps they're desensitised to how fast and sporty a car feels by all those laps of the Nürburgring they undertake. Whatever the reason, the Sport Plus mode in the M850i Convertible is, possibly, a little too extreme. The throttle becomes a little too sharp for smooth progress at low speeds (though welcome as you drive quicker) and the firm damping is complemented by an aggressive calibration of the transmission. It drops a gear or two seemingly every time you even think about braking, gratuitously blipping the throttle in the process.
Use this mode and you'll find yourself slotting the gear lever over into the manual setting and tapping the tactile paddles behind the wheel instead, all the better to control the selected ratio and the amount of evocative popping and banging coming from the exhaust on the overrun. The standard four-wheel steering (Integral Active Steer in BMW-speak) makes the 8 Series shrink around you in the corners and you'll find the confidence to push it faster and harder. Eventually, you'll poorly judge the entry speed (despite the excellent brakes), telegraphed by a smidge of understeer. But instead of backing off, you can squeeze the throttle back on early and the xDrive and rear differential sort it all out for you, firing the car out of the corner and down the next straight in a fury of twin-turbo V8 power. Fabulous.
By this stage you've forgotten you're driving a convertible (except perhaps for the even more audible exhaust) and you've certainly forgotten all about your tee time. To hell with stereotypes.
Verdict
While it was inevitable that BMW would offer an open-topped version of its sexy new 8 Series, it was never a foregone conclusion that it would retain almost all of the Coupe's ability, while still playing the boulevard cruiser card so convincingly (lesser models than the M850i will be better again in that regard). Sure, it comes with the usual cabriolet compromises, but if you're already ok with all that then you'll undoubtedly agree with us that the new 8 Series Convertible is a wonderful creation.
Exterior Design
Interior Ambience
Passenger Space
Luggage Space
Safety
Comfort
Driving Dynamics
Powertrain
