from the brake shoe 96 the adjusting spindle 14 is formed with a parabolic recess 104 which is engaged by a thrust element 106 of an eccentric apparatus 108 the eccentric apparatus 108 serves to transmit the mechanical brake actuation at the front side of the brake piston 8 a cylindrical recess 110 is provided from which an aeration duct 92 leads to the annular chamber 94 between the sealing elements 56 64 fig3 shows an adjusting nut 16 in which the friction cone 88 is inclined from the front side of the adjusting nut toward the bore 15 that is to say inwardly the cone 90 is thus formed at the inwardly projecting cylinder 22 of the brake piston 8 fig4 shows a pin 112 in the brake piston cylinder 22 pin 112 serves to restore the adjusting apparatus when the brake lining has worn out the piston 8 along with adjusting nut 16 are removed from the housing 2 when the pin 112 is pressed against a pressure plate 114 which is inserted in the adjusting nut 16 the friction cones 88 90 will be separated from each other and the nut 16 can be turned on the spindle 14 back in the direction toward the interior space of the cylindrical bore 4 the main features which result are a functionally reliable adjustment in the pressureless condition no seizing due to an expansion of the caliper cost effective manufacture and operating errors not affecting the adjustment furthermore an extruded piston is utilized with an internal brake cylinder 22 and brake cone for the transmission of the force of the parking brake an extruded bushing 16.