The car was launched in 1948 along with the smaller-engined Sunbeam-Talbot 80 but many features dated back to the pre war Sunbeam-Talbot Ten. The body was completely new and available as a four-door saloon or two-door drophead coupé. The saloon featured a "pillarless" join between the glass on the rear door and the rear quarter window.
The car went through three versions before the name was changed to Sunbeam MkIII (without "Talbot") in 1954. It was the last car to bear the Sunbeam-Talbot name.
Sunbeam-Talbot 90 MkI 1948–1950
The original version had a 64 bhp (48 kW) 1,944cc side-valve four-cylinder engine derived from a pre-war Humber unit carried over from the Sunbeam-Talbot 2-Litre.
The chassis was derived from the Ten model but with wider track and had beam axles front and rear and leaf springs.
The brakes were updated to have hydraulic operation. Saloon and Drophead coupé bodies were fitted to the chassis and the rear wheel openings were covered by metal "spats".
4000 were made.
Sunbeam-Talbot 90 MkII 1950–1952
The Mk II got a new chassis with independent front suspension using coil springs. The engine was enlarged to 2267cc and the cylinder head changed to overhead valves. Power was up at 70 bhp (52 kW). The front of the body was modified; the headlights were higher and there were air inlet grilles on either side of the radiator
A Coupé version tested by The Motor magazine in 1952 had a top speed of 85.2 mph (137.1 km/h) and could accelerate from 0-60 mph (97 km/h) in 20.2 seconds. A fuel consumption of 22.5 miles per imperial gallon (12.6 L/100 km; 18.7 mpg-US) was recorded. The test car cost £1393 including taxes.
5493 were made.
Sunbeam-Talbot 90 MkIIA 1952–1954
The Mk IIA engine had the same 2267cc capacity with the cylinder head and overhead valves, but had a higher compression engine raising the power output to 77 bhp (57 kW).
To cater for the higher speeds the car was now capable of the brakes were enlarged.
To improve brake cooling the wheels were pierced.
The Talbot MkIIA coupe/convertible is regarded as the rarest of the Sunbeam Talbot's.
The rear wheel spats were no longer fitted.
10,888 were made.
Sunbeam Mk III 1954–1957
From 1954 to 1957 the car continued, but without the Talbot name and was marketed as the Sunbeam MkIII and badged on the radiator shell as Sunbeam Supreme. The drophead coupé was not made after 1955.
There were some minor styling changes to the front with enlarged air intakes on each side of the radiator shell and three small portholes just below each side of the bonnet near to the windscreen. Duo-tone paint schemes were also available.
Engine power was increased to 80 bhp (60 kW) and overdrive became an option.
A Mk III tested by The Motor magazine in 1955 had a top speed of 93.6 mph (150.6 km/h) and could accelerate from 0-60 mph (97 km/h) in 17.4 seconds.
A fuel consumption of 22.1 miles per imperial gallon (12.8 L/100 km; 18.4 mpg-US) was recorded. The test car cost £1191 including taxes.
The main Rootes Group dealers in Leicester, Castles of Leicester, offered a conversion that moved the gearchange to the transmission tunnel, modified the cylinder head, fitted a bonnet air scoop and changed the way the boot lid opened.
These models were not connected with the Sunbeam factory but are sometimes referred to as the Mk IIIS. Some 30-40 cars were modified. The revised gearchange was also offered as an after market accessory and was suitable for fitting to earlier models also.
Approximately 2250 were made.
A Mk II was driven by Stirling Moss to take second place in the 1952 Monte Carlo Rally.
A Sunbeam Mk III was outright winner of the 1955 Monte Carlo Rally.