The Riley RM is a series of executive cars and compact executive cars that were made by Riley Motors from 1945 until 1955. They were the last models developed independently by Riley before its parent company, Nuffield, merged with Austin to form BMC. The RM series was produced in Coventry until 1949, when production moved to the MG works at Abingdon. Until 1952, models were marketed as the Riley 1½ Litre and the Riley 2½ Litre. the term RM has been used retrospectively to encompass models produced before 1952.
There were four types of RM vehicles produced. All used Riley engines with four cylinders in-line, hemispherical combustion chambers and twin camshafts mounted high at the sides of the cylinder block.
The RMA was a large saloon, and was replaced by the RME. Both used a 1.5 L (1,496 cc) 12 hp (RAC Rating), developed before WWII.
The RMB was a longer car, and it was replaced by the RMF. Both cars used a larger engine, new in 1937, a 2.5 L 16 hp (RAC Rating) "Big Four".
The RMC and RMD were limited-production cars, an open 2 or 3-seater Roadster and a 4-seater drophead.
The Riley Pathfinder was the RMH, and was the last saloon to be built with the Riley Big Four engine.