Abstract: For the determination of the friction/slip characteristics of the tires of a road vehicle which is equipped with an antilock system designed for an individual wheel control, in an initial phase of a controlled braking, only the wheel brake of an individual vehicle wheel is acted upon by brake pressure and the latter is dimensioned so that the result is the initial retardation in accordance with the driver's wish. During this initial test phase of the braking, the absolute brake slip .lambda..sub.B as well as the friction utilization .mu..sub.B linked therewith is continuously determined as soon as, as a result of just the braking of the test wheel, the vehicle retardation z increases no further and/or the braked vehicle wheel is more strongly retarded than corresponds to a predetermined threshold value, the test braking is interrupted and the braking is continued by pressure action on the further vehicle wheels; corresponding test braking phases are carried out in cyclic sequence for all guidance wheels.

Abstract: A slip control system determines friction/slip characteristics of tires of a road vehicle equipped both with an antilock system to permit an individual brake pressure control on individual vehicle wheels. The front wheel brakes are connected to a primary output pressure space of the tandem master cylinder, and the rear wheel brakes are connected to a secondary output pressure space of the tandem master cylinder. A first bore stage of a housing of the tandem master cylinder forms a housing-defined boundary of the secondary output pressure space. An inner piston flange movably seals off a pressureless downstream chamber in relation to an inner portion of the first bore stage. An intermediate wall of the housing delimits the bore stage relative to a central bore stage which extends from a third bore stage receiving a primary piston.