1969 was a tumultuous period in the motorcycle industry, marked by the rise of the Japanese and the beginning of the end of the British. Against such a rapidly evolving consumer sentiment, BMW introduced the /5 Series (“slash five”) for the 1970 model year. In three years of production, the /5 motorcycle series continued. energizing the brand with a modern design and unleashing BMW’s legendary Type 247 Boxer Twin “Airhead” engine, variants of which will continue to propel the brand’s R-Series motorcycles into the future. next generations. 25 years.
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The /5 series, built at BMW’s newest facility in Spandau, Berlin, comes in three variants. R 50/5 (500cc) is the most affordable, R 60/5 (600cc) is mid-range and R 75/5 (750cc) is the most advanced.
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Compared to its predecessor, the BMW /2 Series, the /5 Series is a completely modernized redesign from the ground up. It boasts an updated 12-volt DC power system complete with a 180-watt alternator, electric starter, more powerful drum brakes and a host of other notable upgrades. The frame is made of tubular steel with twin downward mounts for the motor, similar to the standard Norton Featherbed. A rear subframe is bolted to the main frame and serves as the upper support for the twin rear shock absorbers. Up front, the former /2’s Earles forks have been replaced with telescopic upper /5, signaling a shift in focus on function from handy sidecar duties to improved handling like a single motorcycle.
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Of course, no discussion of the BMW /5 would be complete without considering the Type 247 “Airhead” Twin Flat engine. The company took particular care in designing a simple, reliable engine to solve. address previous concerns about crusher/2. To this end, the 247’s chain-driven camshaft runs below the crankshaft, allowing gravity to assist in oil delivery to the camshaft and eliminate the periodic complete tearing required to maintain “oil slide” of the previous /2 design. Two valves in each hemispherical cylinder head are actuated by the camshaft via couplings, push rods and swingarms. The 70.6mm stroke remains constant in the /5 line, with the 67mm, 73.5mm and 82mm bores determining the displacement of the R 50/5, R 60/5 and R 75/5 respectively.
The R 50/5 and R 60/5 models are equipped with a 26 mm Bing sliding carburetor, while the R 75/5 have a 32 mm Bing CV carburetor. On all models, engine power is sent via a single-disc dry clutch to a powerful 4-speed transmission and then to a final transmission mounted on a swingarm via the shaft.
For the late 1973 models, BMW extended the rear swingarm by about 2 inches, resulting in the so-called “Long Wheelbase” /5. The hallmark of a long wheelbase model is the welds on the final drive side of the swingarm, where the factory has added the extension. The wider clearance allows for a larger battery to be placed behind the engine and gives the driver more space between their shin and the carburetor. To this day, five out of five enthusiasts hotly debate whether the more responsive handling of the original short-wheelbase models outweighed the high-speed stability of the original models. long wheelbase version or not.
Either way, at just over 460 lb., the R 75/5 is one of the lightest 750 cc bikes of the time, and with a top speed of 109 mph, it’s also one of the fastest. best.
Complementing these functional upgrades to its new line of motorcycles, the /5’s aesthetic is also an interesting differentiator from the more bleak old BMWs. While originally only available in white, black, or silver for 1970-71, the 1972-73 models were available in seven colors, including Monza Blue and Granada Red. Even more shocking to traditionalists, 1972 saw the introduction of the 4-gallon “Toaster” fuel tank, which featured prominent chrome trim panels on each side. Although excessive chrome plating on a BMW was heresy at the time, today the Toaster-tank /5 is considered valuable to collectors, as it was only produced for the model years. 1972-73.
Contrary to initial worries from BMW traditionalists that the company had strayed too far from its roots of function rather than form, the /5 family of motorcycles has earned a top reputation for reliability. reliable as an anvil. As classic European motorcycles, the /5 have certain idiosyncrasies of course, but overall, the design and construction are strong. As a testament to their outstanding quality, these motorcycles are still commonly used as a daily vehicle more than 50 years after they were first manufactured.
Experienced owners affirm that with timely maintenance, these bikes are almost indestructible. In fact, properly running /5 cars with over 100,000 miles is the norm at BMW rallies around the world. I met the owner of one, the late Fred Tausch, at a rally in 2004. Tausch’s 1970 R 60/5 had more than 600,000 miles on the clock and was still running when its owner passed. life. Details are sketchy, but it is believed the engine has only been overhauled twice during this remarkable service run.
The classic BMW motorcycle community is an active one, with ample technical support and a well-organized network of enthusiasts (aka “Airheads”) who regularly gather to race congrats on their favorite machines. Parts are still plentiful, though they have grown more expensive over time.
In the end, Series /5 represents a dramatic gamble that will initially but ultimately win for BMW car. These motorcycles are not a cautious evolution of the existing /2 designs that loyal fans of the brand have come to expect. The /5 series’ new emphasis on performance and style, combined with a significant price increase over the /2 Series it replaces, could easily cause the market to crash. Fortunately, that was not the case and /5s became a mild hit.
