FRANKFURT MOTOR SHOW: Mercedes-Benz S-Class Cabriolet

It’s taken about six official leaks and teaser releases, but now Mercedes-Benz has shown its full hand with the first S-Class Cabriolet in almost 45 years.

Benz has officially announced it will show an AMG version of the four-seat convertible first in Frankfurt in two weeks, complete with 430kW of power and 900Nm of torque.

The bad news is the S 63 Cabriolet won't be produced in right-hand drive and therefore won't be available in Australia.

While it will go with its heaviest punch first, the S-Class Convertible range will eventually spread out to every engine currently available in the sedan, so expect everything from 3.0-litre V6 diesel power to a biturbo V12 for the S 65 AMG, but the S 500 Cabriolet is most likely to arrive here next year.

The sixth model in the S-Class family, the S 63 4MATIC AMG Cabriolet will punch to 100km/h in just 3.9 seconds – faster than a BMW M5.

While it’s all-wheel drive, Benz has taken pains to give its power distribution a 67 per cent rear bias, so it should feel more agile and sporty, even in a car built more for luxury than speed.

It also runs carbon-ceramic brakes, surrounded by 19-inch wheels and 255/45 R19 rubber up front  and 284/40 R19 tyres at the back, though 20-inch versions are optional.

It rides on air suspension with full-time adaptive damping, which can be preset to either Comfort or Sport modes and the AMG version of the Cabriolet has specific front-end elastokinematics, so its steering and handling will be considerably sharper than in the stock Benz versions.

It’s no lightweight, though, with the AWD S 63 AMG Cabriolet weighing in at 2110kg dry, which might not harm its straight-line speed, but pushes its NEDC fuel economy out to 10.4 litres/100km and its emissions to 244 grams/km.

While the headline act comes from AMG, the V8 in the S 500 Cabrio has a not-pathetic 335kW of power and 700Nm of torque from its 4.7 litres, with the torque peak arriving at only 1800rpm.

“After 44 years, we are once again able to offer Mercedes aficionados an open-top car in the S-Class,” Daimler’s board member for sales, Ola Kallenius said.

"The new S-Class Cabriolet symbolises our passion for individual and timelessly exclusive mobility, which we share with our customers.”

Its passenger compartment is steeped in tweaks to keep people comfortable, including the wind protection from the aircap, which pops forward the top rail of the windscreen surround to deflect wind above and over the cabin. There are also neck-level heating fans, heated armrests, seat heating and climate-controlled air-conditioning.

The roof folds away into its own compartment in the luggage area, taking around 20 seconds to close, and the job can be done at up to 60km/h.

The cloth roof itself has an outer butyl layer to ward off water and wind noise, while there are also double-glazed windows and an insulating layer inside the roof itself.

There are several remarkable things about the S-Class Cabriolet, which go beyond the 44-year gap to its predecessor. Most curious is that its body-in-white weighs no more than the one the S-Class Coupe is built on, with its rear bulkhead made of aluminium and magnesium and aluminium rear floor both helping to pull its weight down.

The closest relative in the six-car family (including the Maybach and Pullman giants) is the S-Class Coupe, which shares around 60 per cent of the Cabriolet’s body structure parts.

The Cabriolet is 5027mm long, 1899mm wide and 1417mm high, making it considerably bigger than the two-seat SL that is its closest convertible Benz sibling.

It has taken Benz’s R&D department an age to figure out how to create a big convertible that’s not monstrously heavy, and much of that time has been spent adding lighter materials into the body structure.

There is the aluminium rear floor, which the Coupe doesn’t have, and die-cast aluminium longitudinal members, with variable wall thicknesses along their lengths.

The aluminium/magnesium rear bulkhead is also strong enough to support the extendable roll bars, yet still has a through-loading hole, and the car has a number of reinforcing braces beneath the floor for bending and torsional rigidity.

There is a standard rear rollover bar behind the rear head restraints, which is punched up by pyrotechnics (the nice word for “explosives”)

Benz claims the Cabriolet reaches the same bodyshell stiffness levels as the Coupe, while weighing more or less the same as the hard-top.

“Two years after its launch, the S-Class family is now complete,” Daimler’s board member for development, Professor Doctor Thomas Weber said.

“We have never offered six models in the luxury class before – and never before have we enjoyed such success,” he insisted.