Review of the new BMW 3 Series Convertible Range

Sticking to dogma can be a dangerous thing. It can lead us to places we'd rather not go and turn reasonable people into hidebound bores. It can also compromise great cars, ignoring sensible engineering solutions because 'that's the way things are done around here.'

I can think of many examples straight off the bat and BMW's perfect 50:50 weight distribution would probably be one of them. Such weight distribution is fine for their performance M-cars but do you really need perfect balance when you're lugging loads in an estate or cruising in a convertible? Evidently not, as the latest 3 Series drop top features a centre of gravity not measured to millimetric precision in the middle of the car.

Engineering any folding hard top means putting a good deal of metalwork and motors in the rear of the car. In order to get the perfect weight balance, BMW would have needed to undertake radical and costly design changes such as relocating the fuel tank. Of course, you could probably achieve this end a lot cheaper by keeping a bag of cement in the passenger footwell but I couldn't really see Munich green lighting a solution like that. Besides, who really cares if the 3 Series Convertible does have a rearward weight bias? Porsche 911 owners rarely complain.

BMW has been selling 3 Series Convertibles for many years, first through Baur and then manufacturing them in-house, and they've refined the art of building a desirable drop-top very well, the latest Z4 and 6 Series convertible models featuring triple-layered fabric roofs that are about as good as this sort of hood gets. With the 3 Series, BMW felt the time was ripe to follow a divergent path and get with the technology that's driving huge customer demand - folding hard top roofs. Like all the most modern versions, the BMW system is a three rather than a two-piece system.

"The goalposts in this sector of the market look to have subtly shifted"

The advantage of this is that you don't need a distended bottom on the car to accommodate the larger sections of a two-piece roof. The downside of stacking three pieces atop each other instead of two in the boot is that when they're folded, there's not a great deal of luggage space left. With the roof in place, you'll get 350 litres of load space. Fold it down and 140 litres is instantly pared from that figure. That's less than all this car's key rivals - the Mercedes CLK Cabriolet, the Audi A4 Convertible and the Saab 9-3 Convertible. Never mind. From this point the story improves.

The operation of the roof takes a so-so 22 seconds (compare that to 12 seconds for a Mazda MX-5 Roadster Coupe) but there are some real practicality benefits offered. Because of the larger glass rear screen and side windows, visibility has improved by 38 per cent when compared to its predecessor. Not only does this mean that rear seat occupants will feel less claustrophobic, it's also an important safety feature, with cars and bikes less able to sit in your blind spot on motorways. The designers have also factored in some key practicality benefits too. The rear seat backrests can be folded flat to provide additional luggage space if the 210 litres in the boot isn't cutting it. As an option, customers can also specify a through loading facility for bigger items that can still be used with full folding hard top functionality.

Like all the most modern folding hardtops, the BMW system is a three rather than a two-piece system. The advantage of this is that you don't need a distended bottom on the car to accommodate the larger sections of a two-piece roof. The downside of stacking three pieces atop each other instead of two in the boot is that when they're folded, there's not a great deal of luggage space left. With the roof in place, you'll get 350 litres of load space. Fold it down and 140 litres is instantly pared from that figure.

Still, the upside of the folding metal roof arrangement (apart from the obvious security benefits) is that it enables BMW to fit a larger glass rear screen and bigger side windows, so visibility has improved by 38 per cent when comparing this car to its predecessor. Not only does this mean that rear seat occupants will feel less claustrophobic, it's also an important safety feature, with cars and bikes less able to sit in your blind spot on motorways.

The designers have also factored in some key practicality benefits too. The rear seat backrests can be folded flat to provide additional luggage space if the 210 litres in the boot isn't cutting it. As an option, customers can also specify a through loading facility for bigger items that can still be used with full folding hard top functionality.

The 3-Series Convertible line-up starts with the 170bhp 320i SE Convertible which sits below 218bhp and 272bhp 325i and 330i models. Near the top of the standard range, just below the 420bhp V8 M3 model, sits the version that's got everybody in the know excited, the 306bhp 335i Convertible that costs £40,770 in sporty M Sport guise. This is a revolutionary engine insofar as it marks BMW's first turbocharged petrol unit ever offered in an open top car. Flagship of the range is the V8 420bhp M3 model. That only leaves the diesels - the 177bhp 320d, whoch is available in both SE and M Sport guises, the 197bhp 325d and the 245bhp 330d.

BMW customers have a lot to get excited about in the 3-Series Convertible range and dealers are expecting buyers to start flipping their lids in large numbers.

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