The new 'Audax' model for Rootes had its debut at Earls Court 1955 in the form of the 2-door hardtop Sunbeam Rapier. Although it had a monocoque bodyshell by Pressed Steel, it was finished off by Thrupp and Maperley, who also did the Audax convertibles. Mechanically the Rapier was the same as Hillman Minx, but was given a higher compression version of the 1390cc engine with a Stromberg carb and modified manifolds, but a more powerful twin Zenith was quickly offered. In 1958 Sunbeam launched the Series II Rapier with wings along the boot sides, a more traditional Sunbeam grille, and a contrasting side flash. Mechanically a high compression 1494cc engine was fitted together a floor gearchange and revised steering. A convertible Rapier was now offered. The Rapier went to Series III in September 1959, with revised side grilles, a 'landscape' number plate mount, and a narrower side flash on the outside of a new interior. There was also a deeper windscreen. In April 1961 the Series IIIa Rapier gained the 1592cc engine already in the Sunbeam Alpine Series II. The final Rapier convertible was sold in summer 1963, before the roll out of the new Series IV Rapier in late 1963. A brand new Rapier had been designed, but this more expensive car was now released as the Humber Sceptre MkI, and the Rapier given new grilles, rear number plate. Rootes uprated the 1592cc engine to 84bhp with a twin choke Solex. Finally Sunbeam launched the Series V Rapier in September 1965 with a 1725cc version of the 4-cylinder engine, but it was a poor seller and was dropped in favour of the new Arrows Rapier in June 1967 after only 3700 were sold.