the frame for a lower centre of gravity. The compression ratio of the engine was raised from 5.6:1 to 7.0:1, raising maximum output to at 3500 rpm. Despite sharing the wheelbase and track of the other models, the Wartburg bodied roadster was longer, narrower and at a height of just , lower than the standard bodied DA-2 and DA-4 cars. The Wartburg was introduced in 1930, and the Great Depression had drastically reduced the market for sports cars. It was discontinued in 1931, with 150 sold. 3/15 DA-4 The 3/15 DA-4 replaced the DA-2 in mid-February 1931. While the engine, gearing, and chassis of the DA-4 were unchanged from the original Dixi 3/15 PS DA-1, the DA-4 was a step away from the original Austin design. The DA-4 was the first BMW automobile with independent front suspension, which used the ends of the transverse leaf spring to act as lower control arms, with further wheel location performed by two diagonal leading arms. The DA-4 was heavier than the DA-2, and a larger wheel diameter was used to compensate for this. The Austin-based 3/15 series was discontinued before the March 1932 expiration of BMW's licence to manufacture Austin Sevens. It was replaced by the BMW 3/20. Notes References 3 15