Pressed Steel Boxer: 1929 BMW R11

Riding the BMW R11, Alan Cathcart hones in on BMW’s early foray into successful motorcycle manufacturing.

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by Kel Edge

1929 BMW R11
Engine: 745cc air-cooled sidevalve horizontally opposed twin, 78mm x 78mm bore and stroke, 5.5:1 compression ratio, 18hp @ 3,400rpm
Top speed: 62mph (100kmh)
Carburetion: Single 24mm BMW
Transmission: 3-speed, shaft final drive
Electrics: 6v, Bosch magneto
Frame/wheelbase: Pressed steel double cradle/52.4in (1,330mm)
Suspension: Pressed steel trailing-link fork front, rigid rear
Brakes: 7.9in (200mm) SLS drum front, contracting shoe drum on driveshaft, 1.46in (37mm) shoes rear
Tires: 3.5 x 19in front and rear
Weight: 402.6lb (183kg)
Seat height: 28.3in (720mm)
Fuel capacity: 3.7gal (14ltr)

The early days of BMW more than a century ago saw the company born of a struggle for survival, after the 1918 Treaty of Versailles, which ended World War 1, banned the manufacture of aircraft in Germany. BMW (as in Bayerische Motoren Werke AG) had been founded two years earlier in a reorganization of Rapp Motorenwerke, a Munich-based aircraft engine manufacturer, so to stay alive it was forced to turn to making industrial engines, agricultural machinery, toolboxes, office furniture and then finally, in 1923 —  motorcycles.

BMW’s successful struggle to survive was largely funded by Italo-Austrian banker Camillo Castiglioni (no relation to the former owner of MV Agusta!), who was acclaimed as the wealthiest man and most influential financier in Central Europe during World War I, and who was President of BMW AG until 1929. In 1921 BMW had begun manufacture of its M2B15 flat-twin motor, originally designed by its chief engineer Max Friz as a portable industrial engine. But it was also used in motorcycles such as the Victoria and the Helios, and this gave BMW the inspiration to build its own such bikes. So in 1923, BMW launched the R32, the first motorcycle to be badged as a BMW, at the Paris Show. It featured a 486cc wet-sump side-valve engine with horizontally opposed aluminum cylinders and shaft final drive, a flat twin layout which would forever be associated with the marque. At a time when many motorcycle manufacturers used total-loss oiling systems, the new BMW engine featured recirculating wet-sump lubrication, incorporating a drip feed system to the roller-bearing crankshaft — a then-innovative design used by BMW until 1969.

The R32 was the prototype for all future Boxer-engined BMW motorcycles, and employed a tubular steel frame, like its successor models the R42 and R52. These also featured side-valve motors like their ancestor, but BMW also developed the higher performance overhead valve R47 and R57 494cc duo. 1928 saw the appearance of BMW’s first 750-class models, the side-valve R62 and overhead valve R63. The latter remained the sportiest BMW built until the end of the 1920s, with an output of 24 horsepower and a top speed of over 75mph — while like its humbler sister still maintaining the tubular steel frame, with leaf-spring front suspension. 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 also by the Wehrmacht (German army), even before Hitler came to power in January 1933. The increased power and torque of each new generation of BMW engines, coupled with the extra weight of the sidecar’s payload led to the frame fracturing, usually around the steering head, where the welds weren’t up to the job of supporting all that extra weight. The girder forks also had a propensity for collapsing, so something definitely needed to be done.

Order the May/June 2019 issue of Motorcycle Classics to read more about the 1929 BMW R11. Contact Customer Service at (800) 880-7567 or contact us by email.

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