Motorcycle Classics

The BMW RS 255 Kompressor: Making History Going Fast

1939 BMW RS 255 Kompressor
Claimed power:
55-60hp @ 7,000 rpm
Top Speed: 100mph (est.)
Engine: 492.6cc air-cooled DOHC horizontally-opposed 2-cylinder flat twin, 66mm x 72mm bore and stroke w/Zoller supercharger
Weight (dry): 302lb (137kg)

When German BMW rider Georg Meier took the checkered flag in the Senior Tourist Trophy race at the 1939 Isle of Man, it marked the first time a non-Briton had won since the beginning of the TT in 1907.

Meier won the race aboard the exact 500cc BMW RS 255 Kompressor featured here, clocking an average speed of 89.38mph and finishing in two hours, 57 minutes and 19 seconds, a full two minutes ahead of his closest competition, BMW teammate Jock West.


Meier’s win was the culmination of years of development. In the mid 1920s, BMW began experimenting with supercharging — mechanically forcing more air into an engine. Simply put, more air allows more fuel to be burned, increasing the overall output of an internal combustion engine. BMW used Swiss-built Zoller superchargers, and according to author Darwin Holmstrom in his book BMW Motorcycles, these early units, which sat over the transmission connected to the crankshaft by a separate shaft, nearly doubled power output over a normally aspirated engine.

By 1935, BMW’s engineers had moved the supercharger to the front of the engine. The 500cc race engine now featured twin overhead cams driven by side shafts, and a new left side, foot-shift, 4-speed gearbox. With the addition of rear suspension in 1937, BMW’s race bikes handled significantly better than before, and their 500cc race team was winning competitions.

Georg “Schorsch” Meier, who had previously competed off-road, moved to the track in 1938 and took both European and German Championships aboard the BMW RS 255 Kompressor. But the team’s success didn’t follow them to the Isle of Man. During the 1938 Senior TT, teammate Karl Gall wrecked during practice, and his injuries kept him from participating in the race. Then Georg retired on the first lap in the race because of a faulty spark plug. The only saving grace for BMW was Jock West, who finished fifth, one spot better than his 1937 finish.

Prepared to win

In 1939 BMW arrived at the island early and well prepared. Meier, quoted in a story on the BMW Group Press Club USA site, said, “With BMW’s small racing department we arrived in Douglas in good time, since the official practice sessions started 14 days before the race. Early in the morning, at the break of dawn, we were already out there on the roughly 60 kilometre-long island track where people claimed that ‘only an English rider was able to win the race.’ And believe me, the circuit with all its substantial challenges really demanded the utmost of the rider.”

Proof of that demand was, for the second year in a row, another accident involving BMW rider Karl Gall, who came off at Ballaugh Bridge during a practice lap. His injuries were serious, and he died 11 days later.

Although it considered withdrawing, BMW decided to stay in the race, and on June 16, Meier started the Senior TT with 42 other competitors. “I was really under great mental stress at the start, with each rider setting out in 30-second intervals,” Meier said. However, Meier dominated the event, setting a new lap record his first time around and becoming faster on each subsequent lap.

“I was able to complete the seven laps without any significant incidents and I received good news from the pits every time, so that I knew exactly what was going on. Filling up the tank twice in about 17 seconds, which allowed me to change my glasses and have a refreshing drink, went very well.

“And then, after 2 hours and 57 minutes, I at last saw the man with the black-and-white-checkered flag waving me in as the winner. What I really wanted to do most at that point was literally kiss and hug my wonderful machine with its white and blue colors on the tank which, apart from all those flies on the wind deflector, still looked brand new, without the slightest trace of oil or any signs of the incredible race we had just been through.”

While Meier certainly remembered the TT race he won, others were also profoundly influenced by his triumph. One of those people was just 5 years old at the time — world-famous racer John Surtees.

In 1939, a young Surtees would thumb through issues of his father’s motorcycling magazines. In one copy, he found a story with photos about the June 1939 TT races and, more specifically, an image of Meier aboard the BMW RS 255 Kompressor — the image became seared in his mind.

Rule changes

Supercharged engines were banned from international motorcycle racing after 1945, and the Germans, in the wake of World War II, weren’t allowed to compete at the international level again until 1950. But the Germans still competed nationally after the war, and because of this race action some of the supercharged race machines were modified from their pre-war specifications, some even being converted back to a naturally-aspirated configuration.

As Surtees began his own racing career, memories of the BMW began to fade. But in 1955 during a visit to the Nürburgring, he saw images of Meier aboard the Kompressor. “[Those photos] brought back the memories from those early War years,” Surtees says. It wasn’t until 1981 that Surtees gave much thought to the BMW Kompressor. That was when, in Austria at the Oldtimer Grand Prix on the Salzburgring, Surtees saw a restored BMW Kompressor owned by ex-works BMW rider Walter Zeller.

Zeller’s BMW was a factory-modified Kompressor, but Surtees was intrigued. He asked Zeller and Dr. Helmut Krackowizer, the Grand Prix organizer, about the old Kompressor BMWs, wondering if there were any in existence. What he learned sent him on a detective mission.

“It appears that German factories had distributed their racing machines, both cars and motorcycles, around into certain safe locations,” Surtees says. “A Frenchman serving with the French army by the name of Charrier had located what was Georg Meier’s actual machine. Somehow he managed to lay his hands on it and take it back to Paris. In 1946 there are reports of him having taken the machine to two of the early race meetings held.

“But, after having fallen off in the second one and in him getting involved in the opening of a business, the machine languished in a cellar in Paris until acquired by a great BMW enthusiast and dealer here in England by the name of Charles Lock.”

From England to America and back

“Lock, upon obtaining the machine, carried out a considerable amount of correspondence with the factory,” Surtees says, adding, “But as far as I can see he didn’t actually run the machine. This was partly because somewhere between Charrier and Lock the machine had been run without the two percent of castor oil being put in with the fuel and this had caused a seizure of the compressor. Lock carried out some of the repairs. When he decided, after some years, to move to Australia, the BMW was sold to an American associate of his.”

Surtees tracked down the American owner in Boston and traveled to see the Kompressor, which had been disassembled and boxed. Armed with photographs to ensure authenticity of the BMW, Surtees was certain the parts he was looking at did indeed belong to Meier’s machine — and it was in unrestored condition. A price was agreed upon, and in December of 1981, the BMW went to England with Surtees.

Once home, Surtees sent the engine out to Zeller, who agreed to have his works mechanic rebuild the engine to factory specification. Surtees soon had the engine back, but serious work on the BMW was set aside until 1989, when Surtees realized it was the 50th anniversary of Meier’s historic TT win.

“It was only right that this machine should be seen again,” Surtees says. “A big effort was made and finally, just before the Brands Hatch Superprix, it was completed.”

Surtees invited Sammy Miller to join him at Brands Hatch that year to parade his AJS V4, a machine that raced against the BMW in 1939. During the Brands Hatch laps Surtees soon understood why the BMW had been such a successful race machine: It starts with weight — or the lack of it.

BMW used a fully welded steel frame, with taper and oval section tubes. Compared to the typical cast lug and brazed British frames, the BMW chassis was a work of art, and it weighed significantly less than the competition. According to Surtees, the 1939 BMW weighed 302 pounds. Freddie Frith’s Norton was 336 pounds, and Bob Foster’s V4 AJS was 405 pounds. Couple the low weight with tremendous power delivery, and it’s a winner.

“I suppose you could refer to the BMW’s power characteristics as rather like a traction engine,” Surtees says. “It just pulls from virtually zero revolutions. There are no holes or sudden surges, it just responds, you just open up and it goes round the clock to 6,500-7,000rpm with ease.

“The lightness and the way the machine can be positioned make it certainly feel somewhat later than 1939. I recall riding an early plunger Norton in 1950 and don’t recollect that machine having anywhere near the same sort of ride level that this BMW has.

“The power characteristics are very deceptive, and you can easily be lulled into thinking you aren’t going quite as quickly as you are, but what stands out is that this is a real, complete racing machine where everything seems to work well — the brakes, the suspension, the gearbox, and of course the engine.”

Surtees has let Meier’s BMW RS 255 Kompressor return to BMW, where it is in their Mobile Tradition display. However, he still gets to parade the machine at famous racing events. “The BMW Kompressor rightly deserves a place as being one of the all time greats of motorcycle grand prix racing,” Surtees says.

In winning the 1939 TT, both it and Meier became forever etched into motorcycle racing history. MC

Learn more about the BMW RS 255 Kompressor in Built for Speed: BMW 255 Kompressor Engine.

  • Published on Aug 9, 2012
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