The Mini came about because of a fuel shortage caused by the 1956
Suez Crisis. Petrol was once again rationed in the UK, sales of large cars slumped, and the market for German
bubble cars boomed, even in countries such as the United Kingdom, where imported cars were still a rarity.
Leonard Lord, the head of BMC, reportedly detested these cars so much that he vowed to rid the streets of them and design a 'proper miniature car'. He laid down some basic design requirements – the car should be contained within a box that measured ; and the passenger accommodation should occupy of the length; and the engine, for reasons of cost, should be an existing unit.
Alec Issigonis, who had been working for
Alvis, had been recruited back to BMC in 1955 with a brief from Lord to design a range of technically advanced family cars in the same innovative spirit as his earlier
Morris Minor to complement BMC's existing conventional models. Issigonis had set out design projects for three cars – large and small family cars and a very small economy car. His initial work was on the largest car, designated XC9001, with the smallest car, XC9003, having the lowest priority despite it being Issigonis' greatest personal interest. With Lord's dictum to produce a bubble car competitor and his revised design requirements being laid down in October 1956, work on XC9001 stopped and XC9003 became the priority. In addition to Issigonis, the team that developed the Mini included
John Sheppard (who had worked with Issigonis at Alvis),
Jack Daniels (who had worked with Issigonis on the Morris Minor), Chris Kingham (also from Alvis), Charles Griffin (from Cowley), Vic Everton (from the body—jig shop), Ron Dovey (who built the bodies), Dick Gallimore (who laid out the experimental bodies), and George Cooper (whose job was to check the layouts). Together, by July 1957, they had designed and built the original XC9003 prototype, which was affectionately named the "Orange Box" because of its colour. but departed from tradition by mounting it
transversely, with the engine-oil lubricated, four-speed transmission in the
sump, and by employing
front-wheel drive. Drive was taken down to the transmission via a conventional clutch coupled to a set of primary gears on the end of the crankshaft which gave rise to the characteristic transmission "whine" for which the Mini became famous. Almost all small front-wheel drive cars developed since have used a similar configuration, except with the transmission separately enclosed rather than using the engine oil and mounted directly onto the end of the crankshaft, but with unequal length driveshafts. The radiator was mounted at the left side of the car so that the engine-mounted fan could be retained, but with reversed pitch so that it blew air into the natural low pressure area under the front wing. This location saved vehicle length, but had the disadvantage of feeding the radiator with air that had been heated by passing over the engine. It also exposed the entire ignition system to the direct entry of rainwater through the grille. Early prototypes used the existing 948 cc A-Series unit, but this provided the ADO15 with performance far greater than its price and purpose required – a top speed of about . The engine was reduced to a new 848 cc capacity with a shorter
stroke. This reduced power from 37 to 33 bhp and caused a significant drop in
torque, so provided more realistic performance, especially when the ADO15 body was widened by 2 inches (5.08 cm) over the XC9003 prototype, which blunted the car's top speed while improving its stability and roadholding. Even so, the ADO15 had a top speed of , which was better than many other
economy cars of the time. The
suspension system, designed by Issigonis's friend
Alex Moulton at
Moulton Developments Limited, used compact rubber cones instead of conventional springs. This space-saving design also featured rising progressive-rate springing of the cones, and provided some natural damping, in addition to the normal dampers. Built into the subframes, the rubber cone system gave a raw and bumpy ride accentuated by the woven-webbing seats, but the rigidity of the rubber cones, together with the wheels' positioning at the corners of the car, gave the Mini
go kart-like handling. Initially, an interconnected fluid system was planned, similar to the one that Alec Issigonis and Alex Moulton were working on in the mid-1950s at Alvis. They had assessed the mechanically interconnected
Citroën 2CV suspension at that time (according to an interview by Moulton with
Car Magazine in the late 1990s), which inspired the design of the Hydrolastic suspension system for the Mini and Morris/Austin 1100, to try to keep the benefits of the 2CV system (ride comfort, body levelling, keeping the roadwheel under good control and the tyres in contact with the road), but with added roll stiffness that the 2CV lacked. The short development time of the car meant this was not ready in time for the Mini's launch. The system intended for the Mini was further developed and the
Hydrolastic system was first used on the
Morris 1100, launched in 1962; the Mini gained the system later in 1964. As launched, the Mini had simpler suspension made from
conical springs of solid rubber. These were compact, saving on intrusion into the cabin space, and required no maintenance. The conical shape gave the springs a progressive action, becoming stiffer at greater degrees of compression. This gave the ADO15 a smooth ride over small bumps, but minimised roll and pitch on more uneven surfaces. It also allowed the springs to cope with the huge variance in load between an unladen car (about 600 kg or 1300 lb) and a fully laden one (just over 1000 kg or 2240 lb, or a 70% increase). Ten-inch (254 mm) wheels were specified, so new tyres had to be developed, the initial contract going to
Dunlop. Issigonis went to Dunlop stating that he wanted even smaller, wheels (even though he had already settled on 10-inch). An agreement was made on the 10-inch size, after Dunlop rejected the eight-inch proposition. Many features were designed into the ADO15's interior to maximise its passenger and luggage space on top of the major savings allowed by the transverse engine and 10-inch wheels. Sliding windows allowed single-skin doors to be fitted, improving elbow room and reducing costs. A bracing bar was fitted across the door frame to brace the single skin and this was later adapted into a large storage bin on each door. Issigonis later said that he had sized the bins to carry the ingredients of his favourite drink, a
dry martini ==Mark I: 1959–1967==