The Riley RM Series is an executive car which was produced by Riley from 1945 to 1955. It was the last model developed independently by Riley prior to the 1952 merger of Riley's still new owner Nuffield, with Austin to form BMC. The RM series was originally produced in Coventry, but in 1949 production moved to the MG works at Abingdon. The RM models were marketed as the Riley 1½ Litre and the Riley 2½ Litre. There were three 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 12 hp, developed before WWII. The RMB was a longer car: it was replaced by the [|RMF]. Both cars used a larger engine, new in 1937, a 2.5 L 16 hp "Big Four". The RMC and RMD were limited-production cars, an open 2 or 3-seater Roadster and a 4-seater Drophead.
Kestrel
The RM was inspired by Riley Motors' successful and stylish pre-war 1½ and 2½ Litre Kestrel Saloons but the new cars featured a new chassis. The new chassis with its Riley "torsionic" independent front-wheel suspension incorporated the experience of the wartime years. The RM series was new because the patterns of dies for the old models were destroyed in the air raids on Coventry.
Riley RMA
The RMA was the first post-war Riley. It was announced in August 1945 with the news it would become available in the autumn. It used the 1.5 L engine and was equipped with hydro-mechanical brakes and an independent suspension using torsion bars in front. The body frame was made of wood in the English tradition, and the car featured traditional styling. The car was capable of reaching. The RMA was produced from 1945 until 1952 when it was replaced by the RME.
Riley RMB
The 2.5 L RMB was a lengthened RMA launched a year later in 1946. It used the 2.5 L "Big Four" engine with twin SU carburettors, starting with 90 hp but increasing to 100 hp for 1948 with a top speed. The wheelbase was longer and the overall length was a full longer. The RMB was replaced by the RMF for 1952. A car tested by The Motor magazine in 1949 had a top speed of and could accelerate from 0– in 16.8 seconds. A fuel consumption of was recorded. The test car cost £1224 including taxes.
Riley RMC
The RMC was an open 2-door, single bench seat, 2/3-seater version of the RMB, with a large rear deck area and fold-flat windscreen. Announced in March 1948 it was delivered to Geneva just too late to be exhibited at the Geneva Motor Show. Primarily designed for the North American export market it was normally fitted with left-hand drive. The gear change lever was on the steering column. The bonnet and radiator were lowered and the bonnet catches were arranged to be operated internally. Extra over-riders were fitted to the bumpers and the fuel tank was enlarged to 20-gallons. Eighteen months later in September 1949 Riley announced future production would include a small quota of cars with right-hand drive. Riley attributed this to a slight increase in the supply of steel. Instead of side windows it was supplied with flexible celluloid-glazed side curtains with a hole for hand signals and, when deployed, flimsy synthetic roofing over a light metal frame. It shared that car's 2.5 L engine, and could reach. Just over 500 were built from 1948 until 1951. Both the and of the car bore a remarkable likeness to a 1934 Ford V8.
Riley RMD
The RMD was a traditional 2-door cabriolet, the last cabriolet to wear the Riley name. It used the same 2.5 L 100 hp engine as the RMB, on which it was based. Just over 500 were produced between 1949 and 1951. This new body was first displayed in October 1948 at London's Earls Court Motor Show.
Riley RME
Released in 1952, the RME was an improved 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. To improve acceleration the rear axle ratio was changed from 4.89:1 to 5.125:1. When the 2.5 L car ended production in October 1953 a switch to no running boards was amongst many updates to the RME including wholly new shaped front mudguards. Produced from 1952, it was discontinued in 1955 and ultimately its place in the range went in 1957 to the much shorter and unrelated, intended but unused, replacement for the Morris Minor — Riley One-Point-Five also sold as Wolseley 1500, Morris Major and the Austin Lancer. An RME tested by The Motor magazine in 1952 had a top speed of and could accelerate from 0– in 29.5 seconds. A fuel consumption of was recorded. The test car cost £1,339 including taxes.
Riley RMF
The RMF replaced the RMB 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, the last automobile to use the Riley "Big Four" engine, and thus considered to be the last "real" Riley by purists, took its place after 1953 and continued in production until 1957.
Riley 2½-litre Big Four engine
The Big Four engine is a four cylinder 2.5 litre engine rated at 16.07 h.p. under the R.A.C. formula. It was designed in a matter of months, under difficult financial conditions, and announced in the summer of 1937. It followed existing Riley practice, similar to their 1.5 litre engine, but with each cylinder completely surrounded by a water jacket. The fully counter-weighted and balanced crankshaft ran in three main bearings. Pre-war power output was initially, then raised to. In its final Riley Pathfinder form, it developed and was produced until the end of Riley Pathfinder production in February 1957.
