Mercedes-Benz SLS AMG Roadster 2011 Review - International

Mercedes-Benz SLS AMG Roadster

What we liked
>> Thunderous engine note and performance
>> AMG Ride Control
>> Touring ability

Not so much
>> More a tourer than a sports car
>> Dual-clutch transmission can be slow to respond
>> Looks purposeful rather than beautiful

Based on the Gullwing coupe, the Roadster seems on the face of it a slightly unbalanced mix of go-fast grunt and lazy, touring ability. In practice the mix works and lends the SLS Roadster an air of sophistication — what AMG boss Tobias Moers referred to as "high-cool factor".

Mercedes-Benz Australia is looking forward to bringing the Roadster to Australia before the end of the first quarter 2012. For the time being the price remains up in the air, but David McCarthy, Senior Manager for Corporate Communications at Mercedes-Benz in Australia provided hints and back-of-envelope guesses of around eight per cent above the price of the Gullwing. Here at motoring.com.au we anticipate the price of the car delivered to Australian customers should come in under half a million.

Peak power and torque for the engine in the Roadster matches the figures for the Gullwing: 420kW and 650Nm. The engine is an oversquare design (wider bore, shorter stroke) that, coupled to the seven-speed AMG Speedshift DCT transmission, can propel the car to 100km/h from a standing start within 3.8 seconds. Top speed is limited to 317km/h, but in combined-cycle (NEDC) testing the SLS Roadster has posted a fuel consumption figure of 13.2L/100km and CO2 emissions of 308g/km.

Mounted at the rear in a transaxle, the transmission is a dual-clutch box exclusive to the Roadster and the Gullwing. Sixth and seventh gears are overdrive ratios, but the first five gears are all underdriven. At a ratio of 1.03:1, however, the fifth gear is almost a direct-drive ratio.

Drive from the engine to the transaxle is via a carbon-fibre driveshaft running in a torque tube. It's a system shared with both the Gullwing and Benz's C-Class DTM touring car and contributes to the relatively low weight of the Roadster. Four driving modes — C for Controlled Efficiency, S for Sport, S+ for Sport Plus and M for Manual — allow the driver to make the appropriate selection. The SLS also provides Race Start for optimum traction at launch and a mechanical diff lock.

Suspension comprises double wishbones front and rear, while the steering is handled by a rack-and-pinion setup with variable assistance according to road speed. The car's turning circle measures 11.9m.

Composite disc brakes, ventilated front and rear, complement the alloy wheels — 9.5Jx19 at the front and 11Jx20 behind — shod with 265/35 ZR19 (front) and 295/30 ZR20 (rear) tyres.

In length, the SLS Roadster measures 4638mm on a wheelbase of 268mm. Width is 1939mm and the car's kerb mass is 1660kg.

PACKAGING
— More substance and style than Gullwing?
Developed in parallel with the Gullwing, the Roadster weighs 40kg more — but the body in white is just 2kg heavier than the Gullwing's.

As for the Gullwing, the underpinnings of the Roadster are mounted in a rigid aluminium spaceframe, with much of the body also formed from aluminium. The A pillars are constructed from ultra-high strength steel and Benz has tweaked some of the structural members for the Roadster application, to overcome any potential for scuttle shake.

Side sills are thicker, according to Benz, and the dashboard cross-member is reinforced with additional struts, while there's a further curved strut at the rear between the rear bulkhead and the fuel tank — and another crossmember to support the fixed rollover protection system. These changes have resulted in torsional rigidity for the Roadster achieving a figure of 18,000Nm/degree, AMG claims.

The folding soft-top roof of the Roadster can be opened or closed (electrically) within 11 seconds at speeds up to 50km/h. Three colour options available are black, beige and red.

One immediate gripe apparent from driving the SLS through Monaco is that it didn't feel at home in the narrow streets of southern France, where we drove it for the international launch. It's quite a wide car in this situation.

Seat comfort and the driving position cannot be faulted, however. Access is significantly easier in this car than in the Gullwing, since the Roadster has no doors to duck under. When it comes to packaging however, let's state the bleeding obvious here and now. This is a two-seater only and luggage space when the electric roof is down accommodates only two small suitcases -- if you're lucky. Benz reports a boot capacity of 173 litres.

All of that said, the SLS is roomy enough for those two passengers. And unlike some sportscars, the SLS provides enough headroom with the top raised and there's enough legroom for adults to stretch out also.

Any lingering doubts about the looks of the SLS have been shot down by doing away with the steel roof. As a Roadster the SLS seems like a much better proposition in every way...

Eight airbags comprise two adaptive frontal bags, two side-impact airbags in the seats, two kneebags and two windowbags that deploy from the door cappings.

Active safety features include three-stage stability control (ESP on, Sport handling mode and ESP off) and traction control.

COMPETITORS
-- The pros and cons for roofless people
Any prospective buyer is contemplating a purchase price that's expected to be around half a million dollars for the SLS Roadster, so questions of comparative pricing fade into insignificance.

As a for instance, of four cars we consider comparable to the SLS from the target buyer's point of view, just one — the Lamborghini Gallardo LP560-4 is more expensive. The other three are the Aston Martin Virage, the Ferrari California and the Maserati GranCabrio.

In particular, the Maserati is a real bargain — a snip at just $328,000. It's a great looking car too, but it doesn't offer anything like the performance potential of the SLS. As a matter of fact, practically none of the four rivals mentioned can compare with the AMG for power, torque and kerb mass. With an acceleration time of 3.8 seconds to 100km/h the SLS is quicker than all of them.

Setting aside any other consideration, the Mercedes badge is worth quite a lot to a prospective buyer too, although maybe not in the stratified atmosphere of this market sector. There's no denying the SLS is a capable car also, but if you're in the market for this sort of machine style counts for a great deal — and maybe that's where the SLS will struggle against the competitors listed.

ON THE ROAD
— Recalling Mille Miglia triumph in Monaco
There's enough Benz racing heritage in the SLS Roadster for people who have always loved watching V8 Supercars at Bathurst, but now aspire to the finer things in life. The drop-top SLS is a capable tourer — more a tourer than sports car, in fact, as we learned when motoring.com.au drove the new sports car along the narrow, winding roads north of Monaco.

For all its refinement and unmistakeable sophistication, the SLS feels raw. It's how advanced technology can revive musclecar-era nostalgia without compromising safety, comfort and convenience.

As an example, the Roadster presents the naturally-aspirated 6.2-litre engine in its purest form. Between the enhanced output from the engine and the constant presence of the dramatic exhaust note with the top down, the 6.2 is at its outstanding best in this car. Performance is manic, although the dual-clutch seven-speed transmission and the car's electronic safety nannies do all in their power to hold back the awesome brutality of the engine.

Built around a very rigid aluminium spaceframe, the SL exhibits none of the wobbles you might feel in lesser open-top cars. But for all its lightweight construction and rigidity, the SLS feels hefty in corners. Particularly in tight hairpins you notice the weight and the car's propensity to plough on if not handled right.

Left in the Comfort ('Controlled Efficiency') setting or even the Sport and Sport+ modes, the SLS is not very forgiving if you leave the braking too late. It will understeer into the corner. But it turns in much better if you get the braking out of the way early – just like the advance driver trainers teach you!

Where AMG has come to the rescue though, is its AMG Ride Control system, which eradicates some of the handling vices in the SLS Roadster. And the brakes in the SLS felt strong and capable, as indeed they should for their size and actual stopping power.

Ride comfort in almost any mode is commendable. In Sport and Sport+ modes over poorer surfaces the car doesn't so much buck and jump around; but rather ride along with the changing surface of the road. So what you get is not impact harshness that will rattle your dentures, it's more like a showground ride — plenty of sudden changes in direction vertically, but well controlled nonetheless.

The drive program for the SLS took place in France mostly, but still provided a taste of Sir Stirling Moss's famous 1955 win in the Mille Miglia, driving a Mercedes 300 SLR. Of course Sir Stirling and his navigator, Denis Jenkinson, had to work a bit harder to achieve their triumph and they had none of the modern-day features the SLS has to offer.

But that's much of what appeals about the SLS Roadster; it will fry tyres and leave the neighbours suffering heart palpitations when the engine starts and it echoes the Benz motor sport legacy of yore... Yet it can cover long distances in immense comfort and safety.

So spend the extra money if you have it. And choose the Roadster over the Gullwing, because the Roadster is the better car.

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