It was just a matter of time before AMG came up with an open top version of its SLS, and they’ve now announced that such a car will debut at the Frankfurt show in September. For now, the 571 hp roadster is undergoing endurance and quality tests – the car you see here is only lightly disguised with taped up badges and lights.

The AMG team have already completed most of the design work, as the Coupé and Roadster were created in parallel. So the focus of the specialists in Affalterbach was particularly on bodyshell rigidity, handling dynamics, the soft top and NVH.

There are no trademark Gullwing doors here, because it’s just not possible. But an open top car also compromises rigidity, so to ramp up the rigidity of the bodyshell, the cross-member carrying the dashboard has additional supporting struts at the windscreen frame and at the centre tunnel.

A strut mounting stay between the soft top and the fuel tank makes the rear axle more rigid. There’s also a reinforcing cross-member behind the seats which supports the fixed rollover protection system. It also accommodates the subwoofer of the Bang&Olufsen system as there’s no parcel shelf here as in the Coupe.

It was also necessary to have more robust side sills, but not to meet crash requirements, as in principle the Roadster would also pass tests with the side sills of the Coupe. AMG says it’s for driving dynamics, so the Roadster gets side sills with greater wall thickness and chambers. All in, the bodyshell of the Roadster tips the scales at 243 kg compared to the 241 kg weight of the Coupe.

The three-layered fabric soft top can be opened and closed in just 11 seconds at the touch of a button, at speeds up to 50 km/h. When opened, it tucks behind the seats in a Z-formation to save space. The magnesium/steel/ aluminium construction is lightweight and designed for speeds up to 317 km/h, verified at Papenburg, Nardo (Italy) and Idiada (Spain) high speed tracks.

It’s also subject to the standardised Mercedes soft top endurance test, which includes 20,000 closing cycles on a stationary test rig and 2,500 closing cycles while on the move, in all weather conditions. There’s also the “Sindelfingen rain test” which includes the hose test, the continuous overnight rain test, fording test, the icing, swirl and high-pressure tests, or the final automatic car wash test.

They should’ve added a “Malaysian thunderstorm test”. Hi res pics after the jump.

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