Run-flat tyres dampen the joy of BMW's handsome 550i saloon

It's often the smallest, seemingly most insignificant details that can make or break a car. Something relatively minor might infuriate so much that it has the ability to put you off a brand for good - all those millions spent developing what a manufacturer thinks is the best yet, poured down the drain. This has happened to me on the odd occasion, but never with a BMW.

Motoring Road Test

Ride along as we test drive the latest models here and around the world.

More from Motoring

I have owned BMWs in the past. In fact, an old 5 Series was undoubtedly the best car I've ever bought and it ran faultlessly for more than 400,000km before I unwisely chopped it in for something vastly inferior. BMWs are extremely well-built machines but, first and foremost, they're drivers' cars. Unashamedly rear-wheel drive (usually), they used to be a bit of a handful for people not used to six-cylinder power going to the rear tyres. And this gave BMWs the edge against some of their rivals because that frisson of danger was a little bit exciting. It made a BMW so much more than just a boring saloon.

That edge is still there, albeit more controlled by the staggering computational power of modern German automobiles. And BMW's visual appeal is back on track with some really nice-looking cars. The latest 5 Series is one of them and, until the barnstorming new M5 bursts onto the scene and changes everyone's game plan, the 550i is the hottest one of the lot.

At the outset it's worth pointing out, in case you didn't already know, that the nomenclature found on the boot lids of BMWs these days doesn't give an accurate indication of what engine is sitting up front. There was a time when it was easy; a 325i was a 3 Series with a fuel injected 2.5L engine, a 735i was a 7 Series with a 3.5L and so on. But the 550i, unfortunately, doesn't come with a 5L mill; it's actually a 4.4L, while the next model down the list, the 535i, has a 3.0L. My brain hurts. So, is what should be called the 544i a duffer or a winner? It's a duffer. But let me qualify that seemingly damning statement with an explanation. The 550i is a truly amazing, brilliant, beautifully built car that's totally ruined by the smallest, seemingly most insignificant detail: its tyres.

BMW has come in for a lot of flak in recent years for its insistence on fitting run-flat tyres across its range of otherwise fine automobiles, and I've driven plenty of them without seeing what all the fuss is about. Yes, the ride has been slightly firmer than it might have been on conventional rubber, and maybe it's because I was driving them on UK roads, but it never really bothered me. However, driving the all-wheel-drive 550i in Abu Dhabi and Dubai for a few days, I couldn't wait to hand it back. Which actually upset me, I might add.

The shame is that, in practically every other respect, this is one of the very best saloons I have ever driven. It looks lovely; it drives superbly, with a turbine-like power delivery; it is tactile and extremely well-engineered; its brakes are awesome; the way it still feels like a rear-wheel drive when the fronts are also putting down the power is extraordinary. But drive over a cat's eye in the road or some of those truly awful white lane marker thingies in Abu Dhabi, and you'd swear there was no air in the tyres and no shock absorbers keeping you insulated from the surface irregularities. Still, let's examine the 550i in a bit more detail. It's not a model you'll see on European roads, where diesels reign, but in the US and here in the Emirates it has managed to get a foot in the marketplace. No doubt that an urban fuel consumption of, at best, 15.4L/100km and the price of fuel in these areas are two factors. And, to be honest, the latest diesels from BMW are so good that you'd never hanker for anything else if you lived in Europe.

It's a twin-turbo V8 delivering a 407hp wallop along with a mighty 600Nm of twist, which combine to give the 550i quite effortless, massive levels of performance. From rest to 100kph takes five seconds flat, which is Porsche 911 territory, and it's electronically limited to 250kph - a speed at which this Bimmer is probably just getting into its stride. You can just about hear a purposeful growl from that fabulous V8, as it's eerily quiet on the move, with excellent levels of noise suppression. Refinement is everywhere, from the feel of the fat-rimmed leather steering wheel to the way the doors thunk shut in that unmistakable Germanic fashion, and the serenity of every single one of its eight gear changes. It's a car that makes you feel good about yourself and I love it.

But back to those infernal tyres.

I'm all for the application of safety advancements in vehicles, provided they add to, rather than detract from, the experience of driving. BMW's optional and rather good "ConnectedDrive" system with its emergency assist features, its clever and intuitive infotainment, its adaptive headlamps, reversing camera with surround view, adaptive cruise control, night vision and (really very useful when driving on the E11) head-up display, all comes together in a cohesive package of features that actually benefit driver, passengers and pedestrians alike.

Run-flat tyres are also, on the face of it, a brilliant idea. With super stiff sidewalls, they're designed to allow you to keep driving even in the event of a blowout. According to BMW, they mean "important meetings or appointments can still be attended on time, as you haven't needed to stop and replace the punctured wheel". They also mean a "weight saving benefit, as no spare wheel or vehicle jack is needed". Both of these statements are true and BMW also advises that, even with no air in the tyre, you can still drive for 80km at a speed of 80kph.

Yet I could live with less boot space to make the room for that spare tyre. I could cope pretty well if that meeting was missed because of a flat. I would gladly get my hands dirty while jacking up the car on the side of Sheikh Zayed Road as thousands of other motorists sped past my stricken BMW. I would be grinning like the village idiot if it meant that my 550i was fitted with normal tyres; ones that felt as though there was at least some air in them.

So, my advice? By all means head down to your nearest showroom and put down a fat deposit on a 550i or any other 5 Series - they're all utterly brilliant cars. Then, when yours is delivered, immediately take it to the nearest tyre depot and swap those boots for some proper ones. Result? Quite possibly the finest four-door saloon in the world.

The Specs

Base price / as tested Dh340,000 / Dh340,000

Engine 4.4L V8

Gearbox Eight-speed automatic

Power 407hp @ 5,500-6,400rpm

Torque 600Nm @ 1,750-4500rpm

Fuel economy, combined 10.4L/100km