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Car reviews - BMW - 6 Series - 645Ci convertible

Our Opinion

We like
Performance, handling, steering, ride quality, sumptuous interior, equipment list, manual availability, distinctive styling, exhaust note, ridigity, rattle-free body, active suspension, fuel consumption, safety features
Room for improvement
Price, boot space, rear seat accommodation, optional adaptive cruise control, kerb weight gain over coupe, seat comfort over long distances, run-flat tyres

22 Apr 2005

LIKE the Man says, this is more a way of life than a means of transport.

If you’re prepared to spend $220,000 or more on a car that really only seats two in comfort and has a less accommodating boot than most small sedans, then it’s clear that you either have the funds to support a back-up car, or have no more than one other special person in your universe.

The BMW 645i convertible is – as is its sibling, the $17,000-cheaper 645Ci coupe – 4.8 metres of pure indulgence. It boasts practically every piece of automotive technology you could imagine, and then adds one or two you mightn’t have thought of.

It is at once sumptuous and massively capable, small in terms of passenger accommodation, yet large in terms of kerb weight and road space occupied.

The 645i comes about four years after the last large BMW coupe - the 840Ci - bowed out, in June 2000, having accounted for just eight sales in the year.

Both coupe and convertible versions of the 645Ci arrived in Australia during May 2004, although in other places the coupe preceded the drop-top by a few months.

If the 8 Series wasn’t really all that successful a line for BMW in Australia, hopes are clearly high for the sumptuous 645Ci duo.

As a convertible it’s 1.8 tonnes of two-plus-two that occupies virtually the same road space as a Commodore, but packs in a lot more technology per cubic metre.

The engine is the same 4.4-litre all-alloy V8 seen in the 7 Series, as is the six-speed ZF automatic transmission. The difference is that 645Ci buyers can specify a six-speed manual ZF box if they prefer.

There’s not a lot to add to the 645’s specs, as you’d imagine, so it’s no surprise that satellite-navigation, a killer sound system and a bucketful of BMW acronyms describing various electronic systems, come with the territory.

The 645 gets "active" suspension in the form of auto-adjusting anti-roll bars that are said to reduce body lean by as much as 80 per cent, active steering that makes the bulky convertible feel more like a go-kart, see-around-the-corner headlights, voice-activated i-Drive and heads-up instrument display.

What may be a surprise is that active cruise control, which matches road speed with that of a slower vehicle travelling ahead, is optional. It’s about the only thing missing though.

The 645i convertible is generally regarded as one of the least confronting to look at current BMWs. There are plenty of recognisable design cues, but fewer that are likely to offend those reluctant to accept anything beyond the norm.

Perhaps the only thing that might make some people step back is the vertical rear window, which slides up and down independently of where the roof might happen to be at the time, and the fabric-covered "fins" that sweep back past the side windows when the roof is up, yet fold out of sight when it’s down.

The roof folds in approximately 22 seconds, and will continue to activate at speeds up to 30km/h to avoid embarrassment at traffic lights when the top hasn’t fully lowered or raised while the vehicle was stationary.

The lines are otherwise well balanced and pleasing. The convertible is suitably aggressive, with the tight-wrapped BMW look emphasized by asymmetrical wheel and tyre combinations (same wheel diameter, but wider and with lower profile tyres at the back). Yet with the same essential profile as the coupe, it’s graceful and lean enough that it doesn’t look as heavy as it actually is.

A lot of strengthening has gone into the soft-top because where its weighty, the coupe isn’t - it comes in 200kg or so below the convertible.

The 645i is actually something of an alloy-fest, a lot of the car eschewing steel, or cast-iron, in the search for minimal weight. Alloy can be found in the suspension, the brake discs (not the friction surfaces), the bonnet and doors. And the weight-saving quest goes further, with special plastics also used on the bootlid and front side panels.

BMW steps around the current fixation with steel-topped convertibles by saying a fabric roof folds into a tighter space (can’t argue with that) and impacts less on vehicle balance because it is lighter (don’t think we can argue with that either).

A plus for the 645i is that, from inside, it feels more like a coupe than a regular canvas-top convertible. A lot of effort has been put into the insulation of the interior from extraneous noises. The rubberised upper roof layer is wind and water-tight, while high-quality "PUR" polyurethane foam helps keep it quiet. Vision with the roof up is also pretty good for a convertible.

With the roof down, the 645i is pretty bluster-free too. Although it’s a bigger cockpit than, say, that of a two-seat convertible, the wind flow is quite well controlled, both by the general aerodynamics and by a mesh wind-blocker that can be fitted to deter airflow from entering the cockpit from behind. The vertical rear window can be brought into play to control turbulence too.

The leather seats, with memory functions provided for both driver and front-seat passenger, have power lumbar adjustment as well as pull-out thigh supports, and are adjustable every which way. They are comfortable enough, but surprisingly not necessarily ideal for long-distance driving, where aches and pains can, and did, develop during our test.

This only slightly compromised its ability as a long-distance car though. Although many customers will use the convertible in a more symbolic sense, the fact is it’s also able to deliver a rather special experience on remote, open, winding country roads.

The 4.4-litre V8 doesn’t start developing its impressive maximum torque until close to 4000rpm, but once those 450Nm come into play it’s rocket booster time.

Underlaid by a deep V8 rumble, the 645i surges through passing manoeuvres so quickly it’s astonishing, and eats up the country miles in such a relaxed way you tend to forget about any niggles with the seats.

The active steering seems to work even better than it does in the 5 Series, allowing the driver to place the car with supreme accuracy. The convertible’s weight only makes it feel more secure on the road.

The ride balances well between firmness and suppleness. The 645i absorbs rough roads effectively, while still feeling firm and solidly planted. The active (Dynamic Drive) suspension’s ability to control body lean clearly plays a part in this, as does the shake and rattle-free body that hardly feels like a soft-top at all.

While the automatic convertible will accelerate past 100km/h in around 6.2 seconds, which is pretty rapid, it’s not too bad on fuel. A country trip will see the computer registering less than 10 litres per 100km, meaning the official average of 11.5L/100km (better than the figure quoted for the six-speed manual) shouldn’t be too hard to attain.

The 645i convertible is pretty safe too. Dual front and side airbags are part of the picture, as are the usual BMW active safety systems like electronic stability control, an ABS system that is specially configured to control braking in mid-corner, and traction control.

Twin pop-out roll bars are located behind the rear seat headrests to protect passengers if the car is inverted.

What didn’t we like? Not much really, because with a car like this there are certain things you accept, like the ridiculously limited legroom in the rear seats and the smallish, pokey boot (although with 350 litres roof-up it’s not too bad).

The discomfort caused by the seats was a surprise though, and the roof-lowering process seemed to take ages, although it didn’t actually. And we might be reactionary, but we’d still prefer a spare to a set of run-flat tyres.

The bottom line? If you are looking to indulge yourself and have better than $200,000 to spend, you could do a lot worse.

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