The BMW RS 255 Kompressor: Making History Going Fast

German racer Georg Meier won the 1939 Isle of Man TT — a first for a non-Brit — on this 1939 BMW RS 255 Kompressor.


| September/October 2012



BMW Kompressor Right Front

George Meier rode this 1939 BMW RS 255 Kompressor to victory in the 1939 Senior TT with a time of 2 hours, 57 minutes and 19 seconds.

Photo by Neale Bayly

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.

Supercharging

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.

Tony Carlos
10/19/2012 7:44:46 PM

Where is a 100 MPH lap claimed? The only place I see 100 MPH in this article is the estimate of the bike's top speed. If it topped out at 100, it certainly didn't average that for a full lap. Curious that no one has tried supercharging bikes since then. Perhaps the failed turbo bikes of the 1980s are still too fresh in memory.


Bruce
10/18/2012 4:48:50 PM

Georg Meier was a great rider but was very definitely NOT the first rider to lap the IOM TT course at 100mph. That feat had to wait almost 20 years until Bob MacIntyre achieved it on a fully-streamlined Gilera four in 1957. Best regards Bruce Cox, UK






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