BMW Isetta 300

4-wheel

BMW made the Isetta its own.

They redesigned the powerplant around a BMW one-cylinder, four-stroke, 247 cc motorcycle  engine which generated 10 kW (13 hp). Although the major elements of the Italian design  remained intact, BMW re-engineered much of the car, so much so that none of the parts  between a BMW Isetta Moto Coupe and an Iso Isetta are interchangeable. The first BMW  Isetta appeared in April 1955.  In May 1962, three years after launching the conventionally modern-looking BMW 700, BMW  ceased production of Isettas. A total of 161,728 units had been built. 

BMW Isetta 250

While it retained the "Bubble Window" styling, it differed from the Italian model in that its  headlamps were fixed separately to the sides of the bodywork and it carried the BMW badge  below the windscreen. The car was also redesigned to take a modified version of the 250 cc  four-stroke engine from the BMW R25/3 motorcycle and the front suspension was changed.  The single-cylinder generated 9 kW (12 hp) at 5800 rpm. The crankcase and cylinder were  made of cast iron, the cylinder head of aluminium. However, the head was rotated by 180°  compared with the motorcycle engine. The twin-bearing crankshaft was also different in the  Isetta power unit, being larger and featuring reinforced bearings. One of the reasons for this  was the heavy Dynastart unit which combined the dynamo and self-starter. The fuel mixture  was provided by a Bing sliding throttle side draft motorcycle carburetor. In addition to  further changes of detail, the BMW engineers enlarged the sump for installation in the car  and cooled the engine by means of a radial fan and shrouded ducting. The power train from the four-speed gearbox to the two rear wheels was also unusual: fixed  to the gearbox output drive was something called a Hardy disc, which was a cardan joint  made of rubber. On the other side of it was a cardan shaft, and finally a second Hardy disc,  which in turn was located at the entrance to a chain case. A duplex chain running in an oil  bath led finally to a rigid shaft, at each end of which were the two rear wheels. Thanks to  this elaborate power transfer, the engine-gearbox unit was both free of tension and well  soundproofed in its linkage to the rear axle. In Germany, the Isetta could even be driven with a motorcycle license. The top speed of the  Isetta 250 was rated as 85 km/h (53 mph).  The first BMW Isetta rolled off the line in April 1955, and in the next eight months some  10,000 of the "bubblecars" were produced.

BMW Isetta 300

In 1956, the government of the Federal Republic of Germany changed the regulations for  motor vehicles. Class IV licences issued from that time onward could only be used to operate  small motorcycles and could no longer be used to operate motor vehicles with a capacity of  less than 250 cc. At the same time, the maximum capacity allowed for the Isetta's tax  category was 300 cc. Class IV licences issued before the change in the regulations were  grandfathered and allowed to be used as before. This change in regulations encouraged BMW to revise their Isetta microcars. In October 1956,  the Isetta Moto Coupe DeLuxe (sliding-window Isetta) was introduced. The bubble windows  were replaced by longer, sliding side windows. The engineers had enlarged the single cylinder to a 72 mm (2.8 in) bore and 73 mm (2.9 in) stroke, which gave a displacement of exactly  298 cc; at the same time, they raised the compression ratio from 6.8 to 7.0:1. As a result,  the engine power output rose to 10 kW (13 hp) at 5200 rpm, and the torque rose to 18.4 N·m  (13.6 ft·lbf) at 4600 rpm. The maximum speed remained at 85 km/h (53 mph), yet there was  a marked increase in flexibility, chiefly noticeable on gradients. 

1956

Engine 295 cc 2 cylinders Power 13 HP Top speed 85 km/h Lenght/width 2,29 m/1,38 m Weight 340 kg