Detroit 2007: your guide to the show - BMW

No more fabric
Next year's new 3 Series Convertible is joining the legion of other drop-tops that have ditched their cloth roofs.

Just like the Volvo C70, Volkswagen Eos, Ford Focus Coupe Cabriolet and many others, BMW is turning to the delights of a folding metal roof.

It's a first for BMW, and will set it apart from Audi and Mercedes, which have promised that their next A4 and CLK cabriolets will stick to cloth.

So what's all the fuss about?
Well, peeling back the roof of a cloth-topped convertible with a knife is a far easier job than getting into a tin top, so it's a lot more secure.

It's also certain to be more refined with the roof up, which is a great plus point when you're cruising down the motorway in the summer rain. BMW says it also improves visibility by 38%.

The difficulty is the added weight the metal roof brings, and the way that weight is shifted backwards when the roof is folded away. BMW has a history, after all, of being obsessive about how 50:50 weight distribution and rear-wheel drive deliver the best in driving pleasure.

We're driving the 3 Series Convertible in a couple of weeks, so come back to whatcar.com to find out how well it drives when you drop the roof (which you do by flicking a switch and waiting 22 seconds).

Metal roofs also rob the boot of more space than a cloth top. The one on the 3 Series reduces the available room from 350 litres roof up (that's 50 litres more than the outgoing 3 Series Convertible) to 210 litres roof down (50 litres less than the outgoing 3 Series Convertible).

Power and prices
From launch, you can have a 218bhp 325i for £33,030 or a 306bhp 335i for £37,895. Eventually the range will expand to include a 170bhp 320i and 272bhp 330i petrols, and a 231bhp 330d diesel.

3 Series Convertible on video
To see the 3 Series Convertible on video, click here.