Mercedes-Benz: Supercar raises the roof

Mecedes-Benz SLS AMG roadster. Photo / Supplied
Mecedes-Benz SLS AMG roadster. Photo / Supplied

Only a handful of New Zealanders will get to own the car described as the ultimate open-air driving experience, the Mercedes Benz SLS AMG roadster.

And they won't get much change from $500,000 for the ride. The tailor-made supercar was unveiled in Australia last week, about 18 months after the arrival Downunder of the "gullwing" SLS AMG coupe on which the soft-top is based.

The coupe cost $450,000 - the roadster will be more expensive still, carrying standard features such as a full leather interior that is optional on the gullwing coupe.

Mercedes-Benz NZ has sold 10 coupes; its regional head office across the ditch has sold 75. Already 10 Australians have put deposits on the roadster. Deliveries will take four months. No word from the New Zealand office yet on roadster buyers here.

The German-built two-seat SLS roadster was developed by AMG alongside the coupe, the spiritual successor to the famous gullwing 300SL model of the 1950s.

The roadster loses the gullwing doors and solid roof in favour of two conventional frameless doors and a folding soft-top.

Offered in three colours - black, red and beige - the triple-layer insulated roof can be lowered or raised in 11 seconds, even on the move at up to 50km/h.

Fitted with a bonded and heated rear window, the soft-top is mounted on a lightweight magnesium, aluminium and steel frame that folds away in a Z shape behind the fixed dual roll-over protection bars.

The roof and its folding mechanism add just 37kg to the overall weight of the topless car. A weight gain of around 3kg to the roadster's body means it tops out at 1660kg against the coupe's 1640kg.

The roadster's luggage space is 3 litres shy of the coupe's 176 litres because of extra strengthening to compensate for the loss of the coupe's roof. But body rigidity is said to be the same as the coupe.

The soft-top's door openings were deepened into the box-section side sills to make up for the lack of step-in headroom of the coupe's high-lifting gullwing doors,

The roadster uses the same AMG powertrain as the coupe, a 6.2-litre naturally aspirated V8 tucked behind the front axle line, mated to a seven-speed dual-clutch automatic transmission mounted on the rear axle.

The driveshaft is carbon-fibre. The transaxle layout allows for a 47/53 front-rear weight distribution, the same as the gullwing model.

The big V8 has dry-sump lubrication. This reduces the height of the engine, allowing it to be fitted lower down in the engine bay for a lower centre of gravity.

It delivers 420kW at 6800rpm and 650Nm at 4750rpm.The convertible can sprint from zero to 100km/h in the same 3.8 seconds as the gullwing. Top speed is said to be 317km/h.

The seven-speed transmission is claimed to change gears in as little as 100 milliseconds, and offers four driving modes - controlled efficiency, sport, sport-plus and manual.

All modes are selected by a rotary knob on the console, and the manual changes are made through steering-wheel paddles.

The driver can also select a race-start launch function that works electronically with a mechanical diff lock for maximum traction on starts.

The SLS roadster - like the coupe - drinks 13.2 litres/100km on the combined cycle, pumping out 311g of carbon dioxide per kilometre.

The SLS roadster sits on the same aluminium spaceframe as the coupe, with some steel strengthening in key safety areas such as the A pillars.

To make up for the lack of a roof, the roadster gets thicker side skirts, additional struts to support the dashboard cross-member against the windscreen frame and centre tunnel, a curved strut between the soft-top and the petrol tank that reinforces the rear axle, and a reinforcing crossmember behind the seats to support the rollover protection system. The overall result, claims AMG, is a roadster that is not only refined but performs as well as the gullwing coupe.

Four-wheel double-wishbone suspension continues the race-engineering theme, with most components such as the wishbones and steering knuckles cast from aluminium for low unsprung weight.

The low-riding chassis squats on a wide track - 1682mm at the front and 1653mm at the rear - further enhancing cornering.

Standard AMG seven-spoke alloy wheels are shod with 265/35 tyres on the front and 295/30 rubber at the rear.

- NZ Herald

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