Mercedes-Benz SLX: The Gullwing’s Lost 1966 Successor

Mercedes-Benz never officially replaced the 300 SL Gullwing — but in 1966, they came close. The SLX was a mid-engined design study conceived to rival the Porsche 904 and reclaim the sporting spirit the 300 SL had left behind after Mercedes withdrew from racing following the 1955 Le Mans disaster.

Development began around 1962 under designer Paul Bracq, who would later pen the beloved 230 SL “Pagoda,” working alongside Italian designer Giorgio Battistella of the Turin-based OSI studio. Early sketches evolved into a 1:5 scale model by 1965, and finally a full-size, 1:1 rolling mock-up — built from wood and plastic, with no interior — completed in spring 1966. The car underwent wind tunnel testing, using the classic “wool tuft” method to visualize airflow, and passed with encouraging results.

Despite that, Mercedes’s board shelved the SLX. Part of the reason was a shift in the company’s technical priorities toward the Wankel rotary engine — a decision that would lead directly to the C 111 program just three years later. The SLX was never shown to the public, pushed into a vehicle depot and left there for half a century. It finally resurfaced in 2016, dusted off for display at Techno Classica Essen to mark 50 years since its creation — a rare glimpse at a road Mercedes-Benz never took.