Abstract: An anti-skid brake system for the automotive vehicle is disclosed which is arranged to increase or decrease the braking oil pressure periodically on the basis of a comparison between the wheel speed and the assumed vehicle body speed. When the state in which the wheel is incipient to lock before the wheel speed is returned to the assumed vehicle body speed, the braking oil pressure is inhibited from being increased, thereby preventing the assumed vehicle body speed from deviating too far from the actual vehicle body speed. This anti-skid brake system can prevent the wheel from being locked due to having the assumed vehicle body speed set to too low a value relative to the actual wheel speed.

Abstract: An assumed vehicle body speed is determined on the basis of the wheel speed detected by a wheel speed sensor for each wheel and a slip value indicating the tendency of locking the wheel is determined for a predetermined wheel speed on the basis of the assumed vehicle body speed and a wheel speed of the predetermined wheel. The braking force is controlled on the basis of the slip value. When no braking force is controlled and when at least one of the wheel speeds for all the wheels detected by the wheel speed sensors is larger than the assumed vehicle body speed previously determined, a new assumed vehicle body speed which follows is inhibited from being renewed to a larger value and the new assumed vehicle body speed is set as a value equal to the previous assumed vehicle body speed.

Abstract: A shift to control for retaining the braking force from the control for elevating the braking force is implemented when deceleration of the wheel exceeds a first predetermined threshold value when the wheels are braked. The first predetermined threshold value is so set as to become smaller as an assumed road surface friction coefficient .mu. is smaller. The first threshold value is further altered to a larger value by altering the assumed road surface friction coefficient .mu. to a higher one when the period of time required from the start of the control for elevating the braking force to the start of the following control for retaining the braking force is equal to or shorter than a predetermined period of time.

Abstract: In an antiskid brake system for a vehicle, the braking pressure applied to a wheel is reduced when the deceleration of the rotational speed of the wheel reaches a predetermined value and is increased when the acceleration of the rotational speed of the wheel reaches a predetermined value after reduction of the braking pressure. In a low vehicle speed range lower than a predetermined vehicle speed, the braking pressure is increased at a predetermined rate when the acceleration of the rotational speed of the wheel reaches the predetermined value after reduction of the braking pressure. The predetermined rate is independent from the rotational speed of the wheel and is changed with the friction coefficient of the road surface so that it reduces as the friction coefficient of the road surface reduces.