brakes. Bodywork was bolted to the much-modified Herald chassis, the outer rails and the rear outriggers having been removed; with structural outer sills to stiffen the overall design. The engine was an four-cylinder with a pushrod OHV cylinder head and two valves per cylinder, using twin SU carburettors. The Herald's rack and pinion steering and coil-and-wishbone front suspension carried over, having derived from systems used by the former Alford & Alder company that had been acquired by Standard-Triumph in 1959. Rear suspension was by a single transverse-leaf swing axle, an arrangement, that unless ameliorated by any of several options, can allow rear tyres to undergo large camber changes during fast cornering, leading to oversteer – a dynamically unstable condition in which a vehicle can lose control and spin. As did many manufacturers who used a swing axle arrangement (e.g., Mercedes, Renault, Volkswagen), Triumph would later modify the rear suspension. In 1970, the rear suspension was decambered, by incorporating what Triumph called a "swing spring". One leaf was eliminated from the stack and only the bottom leaf was attached rigidly to the differential. The remaining leaves were mounted to pivot freely — thereby eliminating the worst characteristics of the original swing-axle design. The Spitfire was an inexpensive small sports car and as such received rather basic trim by today's standards, including rubber mats and a large plastic steering wheel. It was nonetheless considered fairly comfortable at the time, as it had wind-down windows and exterior door locks, as well as relatively full instrumentation. These early cars were referred to both as "Triumph Spitfire Mark Is" and "Spitfire 4s", different from the later Spitfire Mark IV. The "Spitfire 4" name indicated the possibility of the appearance of a six-cylinder version. In UK specification the in-line four produced at 5,750 rpm, and of torque at 3,500 rpm. This gave a top speed of , and a 0 to acceleration in 16.4 seconds. Average fuel consumption was 31 mpg. For 1964 an overdrive became optional to the four-speed manual gearbox. Wire wheels and a hard top were also available. An all-monocoque construction derivative of the Spitfire with pop-up headlamps, named the Triumph Fury, was proposed with a single prototype being built. Spitfire Mark II (1965–67) In March 1965 the Spitfire Mark II launched with a retuned engine, featuring a revised camshaft profile, water-heated intake manifold, and tubular exhaust manifold, increasing power to at 6,000