A Little Fun on the Side: 1941 BMW R75 Sidecar

Once a war machine, and now a piece of history, this BMW R75 sidecar is about as period correct as it can be.

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by Dain Gingerelli

 1941 BMW R75 Sidecar
Engine: 745cc air-cooled horizontally opposed twin, 78mm x 78mm bore and stroke, 5.8:1 compression ratio, 26hp @ 4,000rpm
Carburetion: Two Graetzin Sa 24mm
Transmission: 4-speed w/reverse (low-ratio 3-speed w/ reverse for offroad)
Electrics/ignition: Noris magneto
Frame/wheelbase: Tubular steel/56.9in (1,444mm)
Suspension: Telescopic fork front, rigid rear w/tube springs for sidecar only
Brakes: 9.8in (250mm) drum brakes front and rear, 9.8in (250mm) hydraulic brake for sidecar
Tires: 4.5 x 16in front, rear and sidecar
Weight (dry/stock): 882lb (400kg) with sidecar
Fuel capacity: 6.3 gal (13.9ltr)
Price then/now: NA/$45,000

Motorcycle sidecars constitute the motoring community’s demilitarized zone. As three-wheelers they separate the mundane and predictable world of automobiles and trucks that lumber along on four wheels from the serendipitous lifestyle that motorcyclists passionately enjoy with their free-wheeling two-wheelers.

But more than that, sidecars are just plain fun to ride. Someone once suggested to me that a sidecar is a motorcycle with a little fun on the side. Perhaps that’s an oversimplification, but it’s true. There’s something magically intoxicating about a sidecar that attracts all sorts of people to admire the odd-looking vehicles.

My first experience with a sidecar occurred in 1979 when I worked for Cycle Guide magazine. Our publication road tested a Harley-Davidson sidecar that summer, so I got plenty of seat time with the Milwaukee-brewed rig. During one outing I stopped at my parents’ house for a quick visit. By chance, Mom and Dad were heading out the door for a dinner date with friends. As the Harley rig and I rambled up to their driveway, Dear Mom greeted me with the biggest smile, followed by, “You’ve got to take me for a ride in that,” her index finger pointing excitedly at the sidecar itself. No matter that she wore a really pretty and delicate evening dinner dress and her hair was prim and proper for her date with Dad, she wanted a ride. I fetched the open-face helmet that we kept stashed in the sidecar for such occasions, and told her to put it on. Then we went for a short ride. She absolutely loved it, this from the woman who, during my formative years, was set against me riding (and racing) motorcycles in the first place.

War wagon

Mike Dunn, who owns Vintage German Motorcycles, enjoys the same kind of interaction with bystanders whenever he rides his World War II-vintage 1941 BMW R75 sidecar featured here. “This thing always attracts people,” Mike says, adding, “and we get all sorts of waves on the freeway when we ride.” By we, he means him and his wife, who by chance had ridden the rig from their home in Riverside, California, to nearby Temecula where they enjoyed lunch at the city’s historic Old Town district a couple days before I photographed the veteran World War II bike. “When we finished lunch and went back to the bike,” Mike recalled, “there was a small crowd around it.” And, he reassured me, everybody had smiles on their faces.

But when this BMW sidecar originally rolled onto the streets of Europe it didn’t necessarily garner favorable looks and childlike grins from bystanders and people along the road. This rig, boasting serial no. 750097, signifying that it was the 96th particular R75 sidecar built, was destined specifically for use by Germany’s Third Reich as a weapon of war. That was June 28, 1941, when war raged all across Europe. By war’s end BMW had turned out an estimated 16,500-18,000 copies of the big three-wheeler.

Design standards

The story of the R75 army sidecar actually has its origins in 1937 when the Wehrmacht’s Oberkommando des Heer (OKH) summoned management from BMW and Zündapp to develop a bike with sidecar capabilities for the military. The new bike would replace BMW’s existing R12, a model with an obsolete rigid frame and an aging flathead engine. The OKH wanted a rig that had a more powerful engine strapped into a frame using rear suspension.

In fact, the Wehrmacht presented a list of mandatory requirements, chief among them that the BMW and Zündapp bikes would share numerous components for interchangeability in the field. For instance, 4.5 x 16-inch tire size was to be used, which also happened to be the same tire size found on the military’s Volkswagen-built Kübelwagen, a Jeep-like all-purpose lightweight personnel transport vehicle. The motorcycles’ fenders were to allow clearance for non-skid chains to be fitted onto the tires, front and rear, and fuel capacity needed to sustain a range of at least 220 miles (350 kilometers). Minimum ground clearance for the two-wheel drive bikes was to be no less than 6 inches (150mm), and maximum speed was set at 60mph (95kph) or more while toting a full load of 1,100 pounds (500 kilograms, the calculated weight of three soldiers and their equipment).

But according to Ian Falloon’s book The Complete Book of BMW Motorcycles, the most important specification was to be the bike’s “marching speed.” As Fallon pointed out, the proposed bike would need the “suitability for sidecar use and the ability to sustain a marching speed of 2 miles per hour without overheating.” That would allow the three-person sidecar to chug along effortlessly and without overheating (something the R12 was prone to do) while traveling alongside infantry on their way to battle.

Both companies submitted designs using boxer-style twin-cylinder engines, but the bikes’ chassis were rather dissimilar. Zündapp equipped its KS750 with a linkage front fork more suitable for heavy loads, while BMW chose a hydraulic fork. Testing proved the BMW’s fork tended to easily compress as the bike’s load increased. In addition, the KS750’s pressed-steel frame was less expensive to manufacture than the BMW’s tubular frame, prompting the German high command to select Zündapp’s entry. But thanks to what amounts to Teutonic tenacity and toughness, mixed with a fair amount of stubborn pride, BMW’s management convinced the OKH to retain their design, too. As Mike put it, “Naturally BMW refused to make a Zünddapp KS750 under license, and so both models [BMW R75 and Zündapp KS750] exist today. But, BMW did agree to build their R75 with the same characteristics of that of the KS750.” And so, while both models utilized a large number of interchangeable components, the BMW R75 that the army accepted retained much of its original design, too.

A versatile engine

As typical from BMW, the R75 engine was stout in structure and powerful in performance. Compression was set at 5.8:1 and the overhead valves were prompted by a single camshaft hunkered deep within the ubiquitous BMW engine cases. The Noris generator and magneto shared the same aluminum drive gear with the camshaft, too. Topside, a pair of Graetzin carburetors received air from a common moist-felt air filter as seen on Mike’s bike; the filter location was later moved topside onto the gas tank for all future models. And to assure that the R75 would accept any fuel that was on hand in a busy war zone, the two low-compression combustion chambers were engineered to burn fuel that seemingly had a combustibility factor only slightly more than that of water. Indeed, reports from the time indicate that, with petroleum being scarce, uber low-grade gasolines and various synthetic fuels often found their way into the R75’s opposed cylinders during the war.

The R75’s two-wheel drive system (both rear wheels) was rather unique, too. Drive initially came from a 4-speed transmission that included another set of numerically high-ratio (low speed) gears for offroad use, plus a reverse gear for maneuverability in a rearward direction (but not intended for retreating from combat!). While conventional gear shifting was accomplished with a left-side foot shift pedal, a hand shifter located on the gas tank’s right side allowed for selecting on-road or offroad gear sets, plus reverse. Positioning the shift lever to the “Gelande,” which stood for “Offroad” setting, selected the low-speed range of gears. Selecting “Strabe,” meaning “Street” in German put the transmission’s high-range set of gears back into play. The power-dividing crown wheel differential at the rear equalized any varying speeds of the two rear-drive wheels while turning, allowing the R75 sidecar to perform as well as a four-wheeler. The low-range set of gears in particular enabled the R75 to climb steep grades. Mike says the half-ton rig is capable of ascending hills with up to 40-degree inclines.

War refugee

Nobody knows for sure when, where or how the war ended for BMW R75 no. 750097, but Mike can trace its history from about 1993, when a motorcycle collector in Austria named Willi bought the bike at auction in France. At the time, the rig was in pieces, but Mike says that the engine and chassis numbers match, so what Willi bought probably rolled as a unit during the war years and beyond. Just how far beyond the end of the war the rig continued to roll is anybody’s guess, but Willi restored the BMW during the 1990s. At some point he sold the restored sidecar to another enthusiast in Austria who wishes to remain anonymous, and who also happened to have served in the post-war NATO-alliance German army as a paratrooper. And that’s where Mike personally picked up the trail.

“I was riding in the Alps when I first saw the R75 sidecar,” Mike recalls. Mike was piloting another World War II vintage sidecar (a Zündapp KS600), with his daughter riding shotgun, and during a fuel stop the R75 rolled up. Mike struck up a conversation with the owner, and they decided to continue their rides together. At the end of the ride Mike and the owner agreed to keep in touch via email, and by sheer coincidence a short time later one of Mike’s friends in California ended up buying the sidecar and brought it home.

“My friend Mark bought it,” Mike says, adding, “I was envious, in a friendly sort of way.” A short time later, though, Mark was busying himself raising funds for another project, so Mike made an offer to buy the R75, selling two bikes, a Zündapp KS500 and a BMW R61, to fund the purchase. That was last summer. “Once I got the R75 I started replacing a few things to bring it closer to being as period correct as I could make it,” Mike reports. “I pound German eBay daily. I’m always trying to find parts for it.”

Pounding the internet has paid off. Mike’s been able to locate items like the period-correct porcelain spark plug caps and the gas primer can affixed between the bike and the sidecar. He cosmetically touched up the license plate to give it a natural-looking patina, and when he learned that R75 sidecars were originally used by one of the German army’s more legendary airborne reconnaissance units, Mike located the proper regimental emblem and stenciled a copy of it to the front and rear of the sidecar. According to Mike, what you see represents the paratrooper regiment known as Fallshirmjäger-Kradshützen-Aufklärungs-Kompanie 1 Abteilung der 2, a unit that played an integral role in the battle for Brest, France, in September 1944.

There’s also a paratrooper emblem on the saddlebag, and if you haven’t figured it out yet, the swivel post that’s positioned at the front of the sidecar typically held an MG 34 machine gun back in the day. The R75 sidecar used by Germany’s Wehrmacht military was never intended to bring smiles to people’s faces.

But that was then, this is now, and today, historic motorcycles like this play an important role in preserving our world history. Perhaps BMW R75 no. 750097 survives to remind us that war is wicked and brutal, and that by taking the high road today we – humankind – should do all we can to prevent future wars. In the meantime, let’s also take the high road so that we can have some fun on the side with our sidecars, no matter what their origin. MC

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