A Chronic of the BMW Motor Bikes
From the beginning on they were built in a very advanced way, with high quality standards and they have maintained their own character until this day. In autumn 1923 the BMW R 32 was presented for the first time. A 500 ccm transverse flat engine with a well fixed transmission, an oil tight universal joint transmission and a torsional resistant double tube frame. 8,5 HP at 330 revolutions per minute, 122 kg light. Of course there had been transvers flat engines with propeller shaft drive before. But the experts admired the genial harmony of putting the elements together to an overall concept, invented by BMW chief constructor Max Fritz. A unified whole easy to handle and and safe.
1925 the first single cylinder engine bike came out, the BMW R 39. Cylinder and crankshaft housing were cast in one piece of light metal. The cylinder sleeve was pressed in.
In the same year the first OHV twin sports model left the mill: the BMW R 37 with 16 HP. It achieved racing victories and won the "Großen Preis von Deutschland".
1926 the BMW R 42 and its sportive sister BMW R 47 were developed. The primitive brake for the rear wheel was replaced by a narrow transmission brake. The engine power improved to 12 HP and 3400 revolutions per minute because of the better cooling of the side valve engine of the BMW R 42.
1928 the BMW R 62 and R 63 with a 750-ccm-engine appeared on the market.
1929 was the first big turning point with the BMW R 11 and R 16. The pressed steel frame - very torsional resistant - was introduced. The tank was fixed on the upper frame. The leaf spring fork was produced of well formed pressings. The bike had drop out axles in the front and the rear. For the first time it was delivered with light, signal horn and speedometer "ready to go". To date these accessories had been considered as extras.
BMW set another miles stone with the models BMW R 12 and R 17 in 1935: the first real telescopic fork with hydraulic shock absorbers. A construction that was taken on world wide. The decisive progress lay in the safe straight ahead guidance of the bike and therefore in a considerable improvement of the handling. The three-speed gear is replaced by a four-speed gear with gate change in the knee pad. For the first time front and rear wheels can be exchanged.
In 1936 BMW makes a revolutionary new constuction: the BMW R 5 with a completely new developed 500 ccm engine with tunnel housing ( 24 HP ). Two camshafts, driven by a timing chain running in a triangle, keep the bumpers short and light- a constructional masterpiece. The four-speed gear has a a completely new type of foot change control and additonally a little hand change control. Probably because they did not quite trust the foot change control. With this bike BMW goes back to the closed triangle double tube frame, electrically welded.
1938 the telescopic rear wheel springing becomes standard for BMW. The shaft drive with the cardan universal joint becomes a real propeller shaft. The side valve engine bikes BMW R 61 and R 71 are mainly used for side car drives.
1940 BMW starts building the BMW R 75 - an off-road vehicle with a driven side car wheel for the Wehrmacht.The OHV750 ccm engine has 26 HP. The combination weighs 400 kg. Very special is the transmission, a variable transmission with four off-road and four normal gears, two reverse gears and a lockable differential gear for the side car drive.
And then came the break down. Only in 1948 BMW was aloud to build bikes with a capacity of 250 ccm. The BMW R 25, built in 1950, was already equipped with a telescopic rear wheel spring. The unstoppable development continued and there was already "green light" for the twin cylinders.
BMW was world wide the first mill that introduced the hydraulic steering dampers. They were one of the top products of the bike production for more than 15 years.
Now the full sprung frame was transferred to single cylinder bikes. The highlight of this development was the BMW R 27 in 1960. It was the quietest single cylinder bike at its time.
End of 1969 BMW started a new series of models. The engines were deliberately constructed as quiet, reliable and fully improved throttle engines, being satisfied with a max. peak output of 6200 to 6400 resolutions per minute.
The great achievements of the BMW designers, engineers and drivers always gave BMW a place in the spotlight. Over the years the BMW bikes gained 206 world records and BMW gained the world's brand name championship of side car bikes 20 years in a row.
Conny Dübel - www.oldtimer-literatur.de - Literatur für BMW