Thus at the Berlin Show in November 1928 BMW displayed an entirely new method of constructing its motorcycles’ frames, the origins of which lay in its acquisition the previous year of the Dixi car company, then making Austin Sevens under licence from the British manufacturer.
The girder forks also had a propensity for collapsing, so something definitely needed to be done. The increased power and especially torque of each new generation of BMW engines, coupled with the extra weight of the sidecar’s payload – which in military use frequently saw two armed soldiers being carried aboard the motorcycle, and often a third on the sidecar, complete with the weight of their rifles and sometimes a machine-gun and ammo – led to the frame fracturing, usually around the steering head, where the welds just weren’t up to the job of supporting all that extra weight. But this frame design was increasingly causing reliability problems across BMW’s entire model range, particularly when a sidecar was fitted as was then becoming increasingly popular especially on the R62 – both for family use, but especially by the Wehrmacht, even in the days before Hitler came to power in January 1933.
The latter remained the sportiest BMW built until the end of the 1920s, with an output of 24 bhp and a top speed of over 120 km/h/75 mph – while like its humbler sister still maintaining the tubular steel frame, with leafspring front suspension. 1928 saw the appearance of BMW’s first 750cc models, the side-valve R62 and ohv R63.
These also featured 500cc side-valve motors like their ancestor, but BMW also developed the higher performance ohv R47 and R57 500cc duo. The R32 was the prototype for all future Boxer-engined BMW motorcycles, and employed a tubular steel rigid frame, like its successor models the R42 and R52.
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