 By 1939, all the major car makers were using unassisted hydraulic brakes; Ford was the last to switch from cable-manipulated systems. Power-assisted Vacuum servo brakes had been invented in 1903, but did not become generally available as an option until the 1950s. Self-adjusting brakes initially were offered on the 1957 Mercury and 1958 Edsel, and other manufacturers soon followed suit. Buick offered power brakes as standard equipment on several of its vehicles by the 1954 model year.
