The Lotus 25 was a racing car designed by Colin Chapman for the 1962 Formula One season. It was a revolutionary design, the first fully stressed monocoque chassis to appear in F1. In the hands of Jim Clark it took 14 World Championship Grand Prix wins and propelled him to his 1963 World Championship title. Its last World Championship win was at the 1965 French Grand Prix.

An early brainchild of Chapman's fertile mind, the original sketches for the car were made on napkins while Chapman discussed his idea while dining out with Frank Costin (designer of Vanwall, Lotus Mk.8, 9, 10, 11 and Lotus 16 bodies, later of Marcos fame). The unveiling of the 25 at Zandvoort in 1962 was a shock for the competition, and particularly for teams like Brabham and UDT/Laystall who had recently purchased 24s from Lotus, with the understanding that they would be "mechanically identical" to the works cars - Chapman reserved the right to alter the bodywork of the cars.

The monocoque made the car more rigid and structurally stronger than typical F1 cars of the period. The 25 was three times stiffer than the interim 24, while the chassis weighed only half as much. The car also was extremely low and narrow, with a frontal area of 8.0 ft², 0.74m² as compared to the normal 9.5 ft², 0.88 m² It was also envisaged to have a column gear lever, to keep the cockpit width to a minimum, although this was only experimental and discarded. To assist the low profile and low frontal area, the driver reclined sharply behind the wheel (an idea seen in the 18, and pioneered over a decade previously by Gustav Baumm at NSU), leading to the nickname 'The Bathtub', while front coil/damper units were moved inboard (as in the 1948 Maserati). The 25 was powered by the Mk.II 1496cc through to the Mk.5 1499cc versions of the Coventry Climax FWMV V8 in crossplane and flatplane formats. Later, Reg Parnell Racing in 1964 fitted BRM P56s of similar specification to their second-hand 25s. Such was the 25's effect on motor racing, even today's modern F1 cars follow its basic principles. Some privateers who had been buying Lotus chassis were disgruntled by the fact Chapman refused to provide them 25s. These teams, including Rob Walker Racing, were given Lotus 24s, while the works team had exclusive use of the 25 for Jim Clark and Trevor Taylor. When it first appeared at the Dutch Grand Prix, the futuristic 25 was inspected by John Cooper, who asked Chapman where he had put the frame tubes in the car.

...
Wikipedia