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 Triumph - GP Grand Prix
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Triumph D2-492-27-11
Photo ou archives : F-M. Dumas

Capacity : 500
Model : GP Grand Prix
Production : 1948 - 1952
Category : (R) Racing


500 Grand Prix - 1948

Birth of a bitza

A dedicated road racer launched in 1948, the Grand Prix Triumph was born out of the company's wartime production of airborne generator sets.

Auxiliary Power Plant

Bombed out of their factory during WWII, Triumph moved into a new factory at Meriden – the reputed geographical center of England. Here they built a special lightweight version of the 500 Speed Twin engine designed by Edward Turner. Intended

to recharge the batteries of Royal Air Force bombers in flight, this "Airborne Auxiliary Power Plant" had a silicon-aluminum cylinders and head.

Triumph over Adversity

It was during a trip to the US that Triumph engineer Freddie Clarke conceived the idea of fitting the all-alloy AAPP engine into the frame of a Tiger 100 equipped with Turner's new sprung rear hub. This bitza (a nickname from "bits of this, bits of that") weighed under 310 lb, developed 10 hp more than the Tiger 100 and even 5 hp more than the all conquering Manx Norton, which was also badly handicapped by the poisonous low-octane gas available in 1946. Dublin fanner Ernie Lyons won the first postwar race in the Isle of Man. The Manx Grand Prix, run in mist and rain, eliminated the favorites. Even when the engine mounts broke, causing a terrible skid on the last Iap, it didn't stop Lyons. Triumph attributed the incident to "loss of attention by the rider." Fast but hairy, the Grand Prix won many minor races but was only available from 1948 and 1952.


Engine: 499cc (63x80mm) air-cooled 360-degree parallel twin four-stroke; aluminium head and block; magneto ignition; dty-sump lubrication

Valves: overhead-camshaft

Fuel System: twin carburetors with separate float chambers

Transmission: 4-speed, chain final drive

Suspension: telescopic forks (front); sprung hub (rear)

Brakes: offset drum (front & rear)

Wheels: 19 inch wire (front & rear)

Weight: 313 lb

Maximum Speed: 120 mph

Production of the fast but tricky Triumph Grand Prix reached only 175 units, most of which were exported to the United States.

Motorcycle encyclopedia Moto Passion, realised by François-Marie Dumas, include almost 2000 photos presented with an exhaustive history of the motorcycles exhibited.

This unique collection has been realised with the participation of many specialists. With many thanks in particular to Yves Campion, Michael Dregni, Didier Ganneau, Jean Goyard, Helmut Krackowizer, Michel Montange, Christian Rey, Bernard Salvat, Mick Woollett, etc

One can order here

  • Original cards on paper (in french)
  • High resolution scans or original documents presented and signed with my name.

Please contact me at for conditions and copyright.

© Tous droits réservés
François-Marie Dumas

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