The “Bubble Window” styling of the BMW Isetta 250 was the same, but there were small differences. The headlamps, for example, were fixed separately to the sides and the body. It also had that modified engine and new front suspension. The Isetta had a four-speed gearbox with power to the rear wheels plus a feature called the Hardy disc.
The Hardy disc was a rubber cardan joint with a cardan shaft on the other side and a second Hardy disc. A duplex chain in an oil bath led to a rigid shaft that led to the rear wheels. This kept the gearbox tension-free and provided soundproofing. The little Isetta with its motorcycle engine could be driven with a motorcycle license in Germany and had a top speed of 53 mph.
The BMW Isetta 600 followed in October of 1956 with sliding side windows, and a larger single cylinder engine that boosted the Isetta to 13 horsepower, but didn’t increase its top speed. Three years after the launch of the BMW 700, they ceased production of the Isetta. A total of 161,728 of the little bubble car were made before production ended.