In 1938, a completely new range was launched with the types BMW R 51, R 61, R 66 and R 71. The most striking innovation was the plunger rear-wheel suspension which had proved so successful in the Six Day Race held in the previous year. The BMW R 51 replaced the BMW R 5, which had been the source of the complex twin-cam engine, as the new 500 cc sports model in the BMW range. In 1941, production of motorcycles for the civilian market was discontinued. When BMW started up production of motorcycles after the war, the BMW R 51 experienced a revival as the BMW R 51/2.