For the 1985 Formula 1 season, Patrick Head finally switched to the carbon fiber monocoque, and the nine chassis of the FW10 were all built at the Williams factories. Initially with pushrod front and rear suspension, the car was then modified by receiving the pullrods at the rear (FW10B). The engine was the 6-cylinder Honda (the collaboration with the Japanese house had started with the 1984 season). At the beginning of the championship the FW10 did not seem very effective but gradually gained competitiveness: Rosberg won in Detroit and especially at the end of the championship Williams began to show giant steps, with Mansell winning the GP of Europe and the GP of South Africa and Rosberg first in Australia. Williams took third place in the constructors' final standing.