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  Lotus 25 Climax
 

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Country of origin:Great Britain
Produced from:1962 - 1963
Numbers built:7
Predecessor:Lotus 24 Climax
Successor:Lotus 33 Climax
Author:Wouter Melissen
Last updated:December 21, 2009
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Click here to download printer friendly versionBig advances in tire development and new regulations for 1961 forced Formula 1 designers to come up with cars both rigid and light. The old tires complete lack of grip benefited from a somewhat flexible chassis for easy sliding around, but by the early sixties the newly found grip levels were a big strain on the traditional tubular frame chassis. Ironically right at this time the sport's governing body decided to decrease the maximum displacement from 2.5 to 1.5 litres. With less power available, saving weight was now a top priority for the designers, but this in turn usually came at the expense of the rigidity. More than anybody, Lotus' Colin Chapman also understood that decreasing the frontal area was of the utmost importance for a competitive design. With these three variables in the back of his mind, Chapman came up with a Formula 1 racer that would revolutionize single seater design and turn Lotus into a regular winner.

Chapman's first purpose built '1.5 litre' racer was the Lotus 24, which used a conventional spaceframe chassis combined with the newly developed Coventry Climax V8 engine. To lower the drag, the cigar shaped body was very slim with the driver almost flat on his back. To make this narrow body possible, the fuel tanks were moved from the sides to above the driver's legs, which resulted in a relatively high polar moment and prevented an even flatter position of the driver. The '24' was very light and narrow, but with the spaceframe chassis, it was still not free of flex. Being intended mainly as a customer car, the Lotus 24 design and production was by no means a secret, which was not the case for the operation in one corner of the factory. For the works team, Lotus was working on a car that was as small and light as the '24', but would also be stiff enough to make the most of the latest tires and the 24's advanced suspension geometry.

At a lunch time meeting with aerodynamics expert and long time associate Frank Costin, Colin Chapman came up with the groundbreaking idea for his new Formula 1 racer. He returned home with some sketches on a napkin and turned them into the design for the first single seater monocoque. While the monocoque principle of the body being the chassis was by no means new, but it was never used for a single seater racer. One of the rare purpose built monocoque racing cars was the Jaguar D-Type, but the weight and complexity of the construction did not make it seem a viable option.

Chapman's design was much more straightforward and consisted of two aluminium pontoons that formed the sides of the car. The two structures were held together on either end by a firewall, creating a tub, which together with subframes for the front and rear suspension formed the chassis. The V8 engine was installed as a semi-stressed member and further increased the rigidity. The aluminium pontoons doubled as fuel tanks allowing for an even lower driving position. Compared to the spaceframe 24, the rigidity of the new, equally light '25' was substantially higher. Using a monocoque was by no means a compromise; the additional benefits were numerous. Only the bottom half of the car was part of the chassis with the rest made up of removable glass reinforced plastic body panels that allowed easy access to all vital parts.

For the opening (non-Championship) races of the season Lotus and the team's main driver Jim Clark used the new Lotus 24 together with the customer teams. It proved to be a competitive car, but not an instant winner, which for obvious reasons did not bother Chapman too much. At the first of the World Championship in Zandvoort, Lotus wheeled out the ace they had kept up their sleeves for a good few months. Jim Clark immediately was the quickest man in the field, which made the 9th place finish due to technical difficulties somewhat disappointing. In the remaining eight races that season Clark racked up three victories, but he was beaten in Championship by Graham Hill, who scored three wins. Now almost a year old, the Lotus 25 was technically still well ahead of the rest of the field in 1963. A better reliability record saw Clark win seven out of the ten races that season, easily winning Lotus' first Driver's and Constructor's titles.

Throughout the 1963 season minor modifications were made to the '25', most noticeable was the installation of a newer version of the Climax engine that had low exhausts instead of the high 'pipes' of the first version. To stay one ahead of the competition, work was started on a successor for the 1964 season. Visibly similar to its predecessor, this Lotus 33 featured so many subtle changes that very few parts were interchangeable. The suspension was completely new to take even more advantage of the monocoque's rigidity and the ever grippier rubber. The 33 also used the latest generation Climax V8, which featured a flat pane crank and mechanical Fuel Injection. To accommodate for this slightly longer engine, the '33' also had a longer wheelbase.

Lotus' competition arrived at the first Grand Prix of 1964 considerably stronger and in larger numbers than before. Jim Clark and the Lotus were still one of the fastest combinations on the grid with five pole positions in the ten races that seasons. Sadly, he managed to convert that speed in only three victories and was beaten in the championship by the more consistent Graham Hill and World Champion John Surtees. For the last season of the 1.5 litre regulations, Coventry Climax introduced a new four valve version of the FWMV engine that brought the Lotus right back into it. Armed with the more powerful engine and fully developed 33 chassis, Jim Clark continued where he left off in 1963 by winning six of the ten rounds in 1965. In the following years 33s equipped with larger engines were used in the Tasman series and even Formula 1, with a lot and very little success respectively. Colin Chapman would go on to win races and championships with innovative designs, starting off with the real Lotus 33 replacement; the Lotus 49, which was the first Formula 1 car with a fully stressed engine.

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  Article Image gallery (54) Chassis (2) Specifications User Comments (3)