The T55 was a stop-gap development of the Cooper T53 for the start of the 1961 Formula One season, pending the introduction of a new chassis to take the Climax FWMV V8 for the new 1.5 litre formula. Smaller and lighter than the T53, it was powered by the 170 hp (130 kW) naturally aspirated Coventry-Climax FPF four-cylinder engine driving through a new Cooper six-speed gearbox.[4][5]