BMW Isetta 600
The 600 was intended as an enlarged Isetta with more power and a more conventional four-wheel configuration.
The front end of the 600 was virtually unchanged from the Isetta, but the 600's wheelbase was stretched to accommodate four seats. A conventional rear axle was added. BMW introduced the semi-trailing arm independent suspension on the 600. This suspension would be used on almost every new model for the next four decades. Because of the increased size and weight, the 600 had a more powerful engine than the Isetta. The 600 had the 582 cc twin engine from the R67 motorcycle. Top speed was 103 km/h (64 mph).
Source: Wikipedia, 2011