The Bentley S1 (originally simply "Bentley S") was a luxury car produced by Bentley Motors Limited from 1955 until 1959. The S1 was derived from Rolls-Royce's complete redesign of its standard production car after World War II, the Silver Cloud. Each was its maker's last standard production car with an independent chassis. The S-series Bentley was given the Rolls-Royce - Bentley L Series V8 engine in late 1959 and named the S2. Twin headlamps and a facelift to the front arrived in late 1962, resulting in the S3. In late 1965, the S3 was replaced by the new unitary construction Rolls-Royce Silver Shadow-derived T series.
The car was announced at the end of April 1955, and it was noted that the existing Continental model would continue. The new standard steel saloon replaced the R type standard steel saloon which had been in production, with modifications, since 1946. It was a more generously sized five- or six-seater saloon, with the body manufactured in pressed steel with stressed skin construction. Doors, bonnet [hood] and luggage locker lid [trunk lid] were of aluminium.
Having a totally new external appearance, although with the traditional radiator grille, the main differences from the R type were:
As with the preceding Mark VI and R type Bentleys, there was almost no difference between standard Bentley and Rolls-Royce models; this Bentley S differing only in its radiator grille shape and badging from the Rolls-Royce Silver Cloud I.
The models shared the 4.9 L (4887 cc/298 in<sup>3</sup>) straight-6 engine. They were the last vehicles to be powered by descendants of the engine originally used in the Rolls-Royce Twenty from 1922 to 1929. The bore was , stroke was and compression ratio 6.6:1. Twin SU carburetors were fitted, with upgraded models from 1957. A 4-speed automatic transmission was standard.
Two wheelbases were produced: and, from 1957, .
A standard-wheelbase car tested by the British magazine The Motor in 1957 had a top speed of and could accelerate from in 13.1 seconds. A fuel consumption of was recorded. The test car, which had the optional power steering, cost ã6305 including taxes of ã1803.
A high-performance version S Continental (chassis only) was introduced six months after the introduction of the S1. Lighter weight fixed-head and drophead coupé bodies were provided to special order (for a premium of about 50%) by H. J. Mulliner & Co., Park Ward, James Young and Freestone & Webb. A pre-production 2-seater fixed-head coupé on the new chassis was designed and built for the Bentley factory by Pininfarina.