In 1946, the company introduced their B-series of bus chassis, with the engine mounted above the front-axle, giving a short front overhang and the door behind the front-axle. The first generation consisted of the B15/B16, the B20/B21/B22 and the B31, primarily divided by weight class, and then by wheelbase. The latter became upgraded in 1948 and renamed 2B20/2B21/2B22 and 3B31. The T31/T32 trolleybus chassis was also available from 1947. In 1950, the next generation was introduced, with the B41/B42, the B61/B62/B63/B64 and later the B83. From then, Scania-Vabis also offered the BF-series chassis, available as BF61/BF62/BF63, which had the engine more conventionally mounted before the front-axle, leaving room for the door on a longer front overhang. From 1954, the B-series came as B51 and B71, and the BF as BF71 and later BF73. In 1959, the B55, B65 and B75, plus the BF75 were introduced, and were from 1963 available as B56, B66 and B76, plus the BF56 and BF76.