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 NSU - 125 Rennfox
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Photo ou archives : F-M. Dumas

Capacity : 125
Model : Rennfox
Production : 1952 - 1952
Category : (R) Racing


125 Rennfox - 1952

The beginning of absolute domination

In 1952, Germany was allowed to return to Grand Prix international racing by the sport's governing organization, the Fédération Internationale Motocycliste. That year, a twin-cam 125cc NSU Rennfox ridden by Werner Haas won the first German Grand Prix.

Starting at the Top

The German GP victory was the beginning of a period of absolute domination for the 125 NSU. Haas, a young rider who was totally unknown at the time – even in his own country – took the world title in 1953 and 1954, beating the Italian MV Agustas and Mondials. In its original version, his twin-cam single developed 12 hp at the start of the 1952 season but hit 14 hp by the time the season ended. Fourteen hp equalled nearly 95 mph on the track.

Running True to Type

Apart from its ignition system, the Rennfox managed to stay pretty faithful to the specification of the production 125 Fox. It retained the same crankcase as well as the pressed steel backbone frame, the leading link front suspension and – in the early days – a swinging fork rear suspension with a single damper concealed in the spine of the frame. That layout was quickly relegated to production models, while the racers gained conventional twin side-mounted shock absorbers. From 1953 to 1954, the engine was lightened and improved. With a single-overhead-cam and six speeds instead of four, it developed 16.8 hp at more than 10,000 rpm and showcased a top speed of 105 mph.


Engine: 125 cc (54x54mm) single-cylinder four-stroke

Power Rating: 12 hp @ 10,500 rpm/ 14 hp @ 11,000 rpm

Valves: twin overhead camshafts

Fuel System: 26mm Amal carburetor

Transmission: 4-speed

Suspension: (front) leading links; (rear) swinging fork

Brakes: (front) twin drums; (rear) drum

Wheels: wire

Weight: 198 lb

Maximum Speed: 93 mph

At the cost of a huge technical effort, NSU obliterated its European rivals and joined the exclusive ranks of the marques that have won a Grand Prix their first time out.

Le fichier Moto Passion réalisé par François-Marie Dumas réunit près de deux mille photos accompagnées d'un historique très complet des machines présentées.
Il sera progressivement mis à jour ici et toute information complémentaire est la bienvenue sur info@moto-collection.org.

Cette documentation unique, qui constitue sans doute l'encyclopédie la plus exhaustive jamais écrite sur l'histoire de la moto, a été réalisée avec l'assistance de nombreux spécialistes dont principalement Didier Ganneau, Christophe Gaime, Mick Woollett, Jean Goyard, Bernard Salvat, Christian Rey, Yves Campion, Helmut Krackowizer, Michael Dregni, Michel Montange, etc. que je remercie ici.

Disponible sur demande :
- Les fiches originales sur papier
- Les photos et archives signées de mon nom en haute définition ou les documents originaux.
Me contacter sur info@moto-collection.org pour les conditions et droits d'utilisation.