Stopping a moving car requires converting its kinetic energy into heat emitted to the atmosphere. For this purpose, friction brakes are used, hydraulically actuated, and on heavy commercial vehicles pneumatically. Drum brakes used for years, lightweight and easy to manufacture, are in modern passenger vehicles mounted only at the rear wheels, and even less and less often. In cars of higher classes, disc brakes on both axles dominate.
HISTORY AND ADVANTAGES
The inventor of the mechanical disc brake is considered to be F. Lanchestera (1902 r.). Hydraulic brakes patented by M. Lockheed at 1917 r. Both ideas were combined, equipping in years 40. in hydraulic disc brakes American performance car brand Miller, a w 1953 r. Jaguar XK, taking part in the race 24 h Le Mans. The first companies to install disc brakes as standard on the front wheels were BMW., Citroen and Triumph. W 1961 r. started installing them on both axes (Fiat, Lancia, Mercedes). They spread in years 60. Their main advantage over drum structures is greater resistance to heat loads. Thanks to this, they are less sensitive to the phenomenon of fading, i.e. loss of effectiveness after long-term use (e.g.. long descent from a steep slope). They are also characterized by greater stability of functioning. However, they do not show the characteristic feature of self-strengthening of action characteristic of their predecessors.. They have higher surface pressures, because the active surface of the pads is smaller than the jaws, and the radius of action shorter. Therefore, disc brakes require vacuum boosters.