|1946 to 1952|
|Production||1946–52 6900 produced|
|Body and chassis|
|Body style||4-door saloon|
|Engine||2.5 L Straight-4|
|Wheelbase||119 in (3,023 mm)|
|Length||186 in (4,724 mm)|
|Width||63.5 in (1,613 mm)|
|Height||59 in (1,499 mm)|
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.
Engine and transmission: Four-cylinders, in-line, with two block-mounted camshafts, and pushrod overhead valve cylinder head. Bore, stroke and capacity 80.5 X 120mm., 2443cc. Maximum power 100bhp at 4500rpm.; maximum torque 1321b.ft. at 3000rpm. Four-speed manual gearbox in unit with engine. Spiral bevel final drive at first, hypoid bevel from 1952.
Chassis: Front engine, rear drive. Separate steel chassis frame, with box-section sidemembers, and tubular cross-bracing. Independent front suspension by torsion bars and wishbones. Rack and pinion steering. Suspension of rear live axle by half-elliptic leaf springs, with torque tube location until 1952. Four-wheel drum brakes.
Bodywork: Coachbuilt bodyshell, with wood framing and steel skin panels, in door four-seater saloon,
Performance: (21/2-litre): Maximum speed 94mph. 0-60mph 16.4sec. Standing 1/4-mile 20.8sec. Typical fuel consumption 21mpg. (lh-litre): Maximum speed 74mph. 0-60mph 25. Isec. Standing IA-mile 22.8sec. Typical fuel consumption 24mpg.
Dimensions: Saloon: length 15ft. 6in.; width 5ft. 3.5in.; height 4ft. 11.5in. Unladen weight 33501b.
In Film and Television
1948 Riley 2½-Litre RMB in No Highway, Movie from 1951
1948 Riley 2½-Litre RMB in Stone of Destiny, Movie from 2008.