Cruising in an 'open-air' convertibles catching on

Cruising in an "open-air" convertible is becoming an increasingly popular way to travel, as motoring editor ALASTAIR SLOANE reports.

It's called "top-down motoring" in millennium-speak, and European carmakers especially are preparing the next wave of soft-top convertibles and folding hard-tops.

Carmakers' love affair with open-air models is growing stronger. Saab sold 18,000 9-3 convertibles worldwide last year and is aiming for bigger numbers this year. BMW's 3-Series convertible has its loyalists. Mercedes-Benz took the fun-in-the-sun concept a step further with the glass roof options on its C-Class sports coupe and upcoming SL.

In America, seven out of 10 Ford Mustangs are convertibles. There is speculation that General Motors will use the new Holden Monaro platform as the basis for a powerful, rear-drive, soft-top hard-top American model.

Many in the next wave out of Europe will be second generations of existing open-air models - updated versions of the Saab 9-3, BMW Z3, Porsche Boxster, Audi TT and Mercedes-Benz SLK.

Some will be soft-top versions of existing hard-tops, like the BMW M3 and new Beetle convertibles. The word in Germany is that Volkswagen will launch the open-air Beetle in California in 2003.

Others, like the fifth-generation Mercedes-Benz SL, will break electronic ground, using active body-control suspension to manage the road surface and electro-hydraulic brakes, a system which uses wires instead of mechanicals to stop the car.

The flagship SL will also use a revised folding hard-top roof from the SLK. The glass top will be available later. The car will be unveiled in Italy in October and arrive here in July next year.

The Japanese have their own luxury folding hard-top, too. It's the Lexus SC430 and it has received pats on the back for its all-round excellence. The build quality is said to be outstanding. The SC430 goes on sale in New Zealand this year.

The new BMW Z3 will appear in Europe late next year. It is said to have all the bulges in the right places and offer improved ride and handling. The Z3 coupe is expected to be dropped.

Mercedes-Benz will take the covers off its new SLK in 2004. This car is expected to borrow styling cues from the upcoming SL and the McLaren Formula One car.

Porsche is likely to offer a heavily revised Boxster convertible in 2005 and Audi will have a new TT roadster in 2006.

The TT will contain more aluminium components. So will the all-new Audi A3, due in 2003. The next-generation Audi A4 will be built on an aluminium spaceframe, so the rumour mill in Europe says.

Audi likes lightweight aluminium and it wants to make more use of it across its range of cars. It already uses it extensively in its A2 city car - being tested in New Zealand at the moment - and its A8 limousine. The bonnet in its A6 is made of aluminium. The suspension components in the just-launched A4 are aluminium.

It uses even more of it in the A4 Cabriolet, to be unveiled at the Frankfurt motor show next month. It goes on sale in New Zealand late next year.

The Cabriolet uses A4 sedan's aluminium suspension - but adds polished aluminium trim. The car's centre console has circular air vents finished in brushed aluminium, just like the TT. The windscreen frame is brushed aluminium and there is an aluminium strip along the car's waistline.

The Cabriolet is based on the four-door but doesn't share a single exterior panel. The interior is different, too. The extended use of aluminium sees to that - so does the all-new dashboard.

The open-top tourer arrives about 10 years after its predecessor, based on the Audi 80/90 of the 1980s. But for reasons best known to Audi it resembles the outgoing model.

The new car's wheelbase is longer by 100mm to extend cabin space for four adults. There is more boot space, too. The body has more than twice the rigidity of the outgoing model, a shell strength that will aid comfort and handling, and roll-over protection - from pop-up bars and an extra strong windscreen frame - is said to be much improved.

The Cabriolet will be available first as a front-drive. All-wheel-drive quattro models will come later. It will be powered by a choice of two V6 engines - a 2.4-litre producing 125kW and a 3-litre unit developing 162kW. The bigger all-alloy engine will have continuous camshaft adjustment.

Standard equipment will include typical safety equipment for the segment, climate-control air-conditioning and power-convertible roof with heated glass rear window.

Carmakers are looking at the use of lightweight materials to help boost fuel savings. Ford Australia, for example, has invested heavily in a magnesium plant in central Queensland.

The use of more aluminium and magnesium in cars, says the industry, will mean fuel savings of about 25 per cent.

In contrast, improved aerodynamics will save 5 per cent; clutchless manual transmissions 10 per cent; cylinder deactivation (shutting down some cylinders when cruising) 15 per cent; continuously variable transmissions (CVT) 20 per cent; stop-start hybrid engines 20 per cent.

The Audi A2 is roughly similar in size to the Mercedes-Benz A-Class. But the aluminium A2 is about 200kg lighter. The new VW Golf-sized Audi A3 is expected to be upwards of 230kg lighter than the current A3. Audi is going on a diet.