1963 was the last season of formula junior. The Lotus 27 was the dominate car of the class. The chassis was a derivation of the Lotus 25 Formula 1 car. The chassis of the 25 and the 27 were of monocoque construction. The suspension was patterned from the Lotus 25 F-1 car. The coil springs and shock's were tucked inside the hull with rocker arms. The first chassis of the Lotus 27 were of steel construction for the inner panels with fiberglass panels on the outer skin. This caused some chassis flex and the fiber glass was soon changed to aluminum. this turned out to be an expensive and time consuming method of construction. The monocoque tub was joined by fabricated steel bulk heads.
The Lotus 27 was a full 5 inches narrower than the preceding Lotus 22.
The Lotus 27 was the most sophisticated formula junior ever made to that point and was not an instant winner, but after a testing and the teething problems solved it became a winner.