There were three types of RM vehicles produced. The RMA was a large saloon, and was replaced by the RME. The RMB was an even larger car, and was replaced by the RMF. The RMC and RMD were limited-production roadsters.
All of the RM vehicles featured the pre-war Riley designed 1.5 L (1496 cc) 12 hp (RAC Rating) or 16 hp (RAC Rating) 2.5 L "Big Four" straight-4 engines with twin camshafts mounted high at the sides of the cylinder block and hemispherical combustion chambers.
The RMA was the first post-war Riley. It used the 1.5 L engine and was equipped with hydro-mechanical brakes and an independent suspension using torsion bars in front. The frame was made of wood in the English tradition, and the car featured traditional styling. The car was capable of reaching 75 mph (121 km/h). The RMA was produced from 1945 until 1952 when it was replaced by the RME.
The RMB was an enlarged RMA and was launched a year later in 1946. It used the 2.5 L (2443 cc) "Big Four" engine with twin SU carburettors, starting with 90 hp (67 kW) but increasing to 100 hp (75 kW) for 1948 with a 95 mph (153 km/h) top speed. The RMB was replaced by the RMF for 1952.
A car tested by The Motor magazine in 1949 had a top speed of 90 mph (140 km/h) and could accelerate from 0–60 mph (97 km/h) in 16.8 seconds. A fuel consumption of 19.6 miles per imperial gallon (14.4 L/100 km; 16.3 mpg-US) was recorded. The test car cost £1224 including taxes.
The RMC was a 3-passenger 2-door convertible version of the RMB with a large rear deck area and fold flat windscreen. It shared that car's 2.5 L 100 hp (75 kW) engine and could reach 100 mph (161 km/h). The car was primarily designed for the North American export market, and just over 500 were built from 1948 until 1951. The gear change lever was moved to the steering column on left hand drive models.
The RMD was a traditional 2-door drophead coupé, the last convertible to wear the Riley name. It used the same 2.5 L 100 hp (75 kW) engine as the RMB, on which it was based. Just over 500 were produced between 1949 and 1951.
The RME was an updated RMA. It still used the 1.5 L four and featured a fully hydraulic braking system. The body had an enlarged rear window with curved glass and from 1954 no running boards. To improve acceleration the rear axle ratio was changed from 4.89:1 to 5.125:1.
Produced from 1952, it was replaced by the Riley One-Point-Five in 1955.
An RME tested by The Motor magazine in 1952 had a top speed of 75 mph (121 km/h) and could accelerate from 0–60 mph (97 km/h) in 29.5 seconds. A fuel consumption of 24.2 miles per imperial gallon (11.7 L/100 km; 20.2 mpg-US) was recorded. The test car cost £1,339 including taxes.
The RMF replaced the big RMB limousine in 1952. It shared that car's 2.5 L "Big Four" engine as well as the mechanical updates from the RME. The RMH Riley Pathfinder, last of the Riley "Big Fours", and thus considered to be the last "real" Riley by purists, took its place after 1953 and continued in production until 1957.
- Enid Blyton