At the onset of WWII, the German army was supplied with sidecar machines in the form of the R12, and to a lesser extent the R71. Midway through the war, BMW introduced the purpose built R75. A robust OHV pushrod engine with 750 cc displacement, coupled with a complex, low geared gearbox, sporting on and off road gearing, as well as reverse, the machine proved its worth on the battlefield. It was a true GS (Gelande Strasse). There was ample power to pull 3 passengers, often with machine gun mounted. Occasionally small utility or ammo trailers were fitted to the rear.
|Photo from wehrmachtgespann.de|
At the conclusion of the war motorcycle production in Germany ceased. It wasn't until 1948 that BMW was again allowed to produce motorcycles, however displacement was limited to 250 cc. The R24, based on the prewar R23 design was produced for two years before Allied forces eased restrictions, and the twin cam 500 cc R51/2 was added to the BMW line-up.
|R24's fresh from the factory line in 1948.|
The racing motorcycles that survived the war (many by being hidden underground, or in hay lofts) were unearthed and circled Teutonic tracks once again.
Those wishing to compete in larger displacement categories, or sidecar divisions, had no options as far as new production. Many ingenious riders took to modifying the well constructed R75WH sidecar motors and placed them in either pre-war or post war plunger frames.
These bikes have been called many things, with monikers including R73 (a cross between an R71 and R75) as well as R51/75. Such bikes were successfully campaigned in solo and sidecar classes.
|R75 Seitenwagen, BMW Group Classic Collection, München|
Also, note the faltenbalge used on the front forks and rear suspension as a weight saving measure.
|R75 Seitenwagen. This machine was for sale a few years ago.|
|R75 Seitenwagen, Zweirad Museum, Neckarsulm|
Unlike many pre- and post war BMW motorcycles, the R75 motor does not easily drop into a plunger frame without some frame modification. The front engine bolt on the R75 actually goes through a boss in the front engine timing cover, instead of the bottom of the crankcase as is typical for pre- and post war plunger motors. As such, one needs to weld to the frame a point of attachment for the front motor mount bolt.
Below are some pictures of a privateer racer with German pedigree. For more information you can check out RCS Racing
|R51/75 Rennmaschine, solo, 1950 (authors collection)|