BMW M850i Convertible Review: Fast, Fun, And Conspicuously Heavy

The recently-revealed M8 might be the fast 8-series everyone is focusing on now, but if you’re feeling impatient, the M850i is already here, and it’s hardly slow.

In fact, when we reviewed the M850i coupe earlier this year, we questioned the need for a full M Division 8-series. The M Performance version of the 8er develops 523bhp from a 4.4-litre V8 and will still happily compact your inner squishy bits while launching you to 62mph in just 3.7 seconds. And if you want, you can do all that with the roof off.

Well, almost. The M850i convertible is about 125kg heavier than the coupe, which means 0-62mph drops by a couple of tenths. But 3.9 seconds to the benchmark 100kmh mark - that’s hardly slow, is it? If anything, with the folding soft-top stowed - something that takes 15 seconds and can be done anything up to 31mph - it feels quicker.

That’s not to say it’s particularly windy in there - so long as the wind deflector is fixed in place behind the front seats, you’re nicely shielded from the outside world. And crucially, there isn’t a pesky piece of metal between your ears and the tailpipes.

The twin-turbo eight-cylinder is enjoyable enough in the coupe, but in the drop-top, it takes on a whole new level of theatre. The muted muscle car-like woofle from the tailpipes means you end up finding excuses to slow down, just so you can put your foot down again.

It’s not the revviest V8, but it is a responsive one - there’s very little lag here. The eight-speed automatic gearbox is good, too - it may not be quite as snappy as a dual-clutch unit, but it isn’t that far off.

There’s little to fault the way the M850i convertible goes in a straight line. But when you arrive at a corner? That’s a different story.

The coupe is already a heavy car, but it just about gets away with it. The drop-top’s extra 125kg is the tipping point - suddenly, the M850i is unwieldy in tighter bends, and keener to slip into understeer, even with the rear-biased all-wheel drive system trying to shake the V8 8er’s ass.

Roll is kept nicely in check, at least, but all that under-body stiffening results in a car that’s just not as wafty as the coupe. The steering’s much the same, but that’s not necessarily a good thing.

It’s fast enough and OK in terms of weight (whatever you do, don’t go for horribly heavy sport plus steering mode), but you don’t really get any feedback from it. The M850i’s steering is just fine rather than being a standout feature. And why do so many modern BMWs have such fat steering wheels?

All of those complaints about bulk can, it must be said, be levelled at the 8-series cab’s peers. Luxury convertibles are inevtiably heavy and aren’t able to hide the bulk. They’re a compromise, and a compromise that you’re generally happy to make because alfresco motoring is rather lovely.

But what a lot of the 8er convertible’s rivals do much better is interior ambience. For a car costing over £107,045, it’s not plush enough in there. The cabin is nicely put together and the tech - gimicky gesture control stuff aside - is all very good, but it’s quite an ordinary space. A Mercedes-AMG S63 cabriolet is so much more successful in this regard, and while a Bentley Continental GTC is pricier, it more than justifies the premium.

This leaves the M850i convertible in a bit of a luxury car no-mans land. The weight blunting the dynamic performance would be more acceptable if it did more elsewhere to justify its price tag, but it just doesn’t. Perhaps it is worth hanging on for the M8 after all…