and has a smaller diameter than the second gear wheel 32 the third gear wheel 34 meshes with a fourth gear wheel 36 which has a larger diameter than the third gear wheel 34 the fourth gear wheel 36 is solidly joined to a fifth gear wheel 38 which has a smaller diameter than the fourth gear wheel 36 the fifth gear wheel 38 meshes with a curved rack 40 whose course will be explained in further detail hereinafter the rack 40 is integral with a brake lining mounting 42 on whose side toward the brake disk 16 the friction brake lining 12 is mounted the brake lining mounting 42 is pivotable about an axis of rotation not shown of the brake disk 16 and is also movable in the direction of the brake disk 16 that is axially to it a second friction brake lining not shown is disposed on an opposite side of the brake disk 16 in a manner known per se it rests in a brake caliper also not shown that is embodied as a floating caliper or in other words is displaceable transversely to the brake disk 16 if the friction brake lining 12 shown is pressed for braking against the brake disk 16 the effect in a manner known per se is a transverse displacement of the caliper which as a result presses the friction brake lining not shown against the other side of the brake disk 16 so that the brake disk 16 is braked the first and second gear wheels 30 32 the third and fourth gear wheels 34 36 and the fifth gear wheel 38 and the.