Released at the London Motor Show of October 1955 the Rapier led the charge of its Hillman and Singer counterparts which were not released until the following year.
The first generation Rapier, under the title of Series I was a stylish two-door hardtop coupé capable of comfortably seating four passengers. The Series I carried the distinction of being the first medium-range auto manufactured by the Rootes Group to carry the "Audax" range of light engineering.
The styling of the Series I Rapier captured the attention of many because of its powerful lines, with a strong North American influence, no surprise since all design work for the car was carried out by US-based Raymond Loewy Associates who had also been responsible for the design on the 1953 Studebaker Hawk.
The Series I Sunbeam Rapier’s appeal was enhanced by its exciting external appearance, coming in a choice of two-tone colour schemes that were highly in demand during the mid-Fifties.
The Rapier came fitted with a 1,390 cc (85 cu in) engine, almost exactly the same as fitted to the Hillman Minx, although all with an increased compression ratio (from 8:1 to 7:1), backed up by a Zenith DIF 36 carburettor, also enhanced by an improved inlet and exhaust manifold layout.
In this enhanced format, the Rapier was capable of developing 62.5 bhp (47 kW) making for considerable acceleration.
The lightweight but powerful Gazelle engine was backed up with four-speed transmission fitted overdrive on third and top gears, an improvement that was gratefully received by potential owners mainly as it came as standards.
One possible design defect was that the car was fitted with a column change somewhat belying its sporting image.
Almost a year after the release of the Rapier Series 1, reportedly due to positive results gained in the regular international rallies entered through Rootes' competition department, the design team at Sunbeam decided to fit the Rapier with an updated engine, replacing the Stromberg carburetor by twin Zenith 36 WIP carburettors mounted on a new inlet manifold.
This extra boost of power allowed the Rapier’s engine to generate 67.5 bhp (50 kW;) increasing its top speed by three mph (4.8 km/h).
A total of 7,477 Sunbeam Rapier Series 1 unit were produced before the model was discontinued in 1958 to be replaced by the Series II.
The Sunbeam Rapier Series II was released early in 1958 and was available in both hardtop and convertible forms.
This time around the Series II came fitted with a more powerful engine, marketed by Sunbeam as the Rallymaster, providing an increased capacity of 1,494 cc (91.2 cu in) and capable of reaching the top speed as 91 mph.
To cope with all the extra acceleration, the Series II Gazelle came fitted with larger front brakes.
To the relief of the growing band of those who preferred the car because of its sporting image, the cumbersome column change was done away with to be replaced by a floor gear change, a modification which had proved successful on the Series I rally cars.
Few cosmetic changes were evidenced between the Series I and II, with among the more significant being the reintroduction of the iconic Sunbeam radiator, which had been considerably shortened and widened, while the spaces on its sides had been fitted with horizontal side grilles.
Sunbeam had also decided to do away with the attractive two-tone lower body colour scheme of the Series I replacing it with a dramatic full-length flash, coordinated to be the same colour as the car’s roof.
The Sunbeam design team had once again drawn from the “American Experience” by fitting the Rapier with a highly pronounced set of fins on its rear wings.
To keep costs down, the leather upholstery, standard on the Series I, was replaced by considerably less expensive vinyl, while overdrive became an extra cost option.
In 1959, the Series II Rapier was discontinued in favour of the Series III. During its production run, 15,151 units (hardtop and convertible) had been built.