Abstract: A traction control system comprising a slip control circuit connected between a slip detector circuit and a hydraulic brake control mechanism. Normally, the slip control circuit acts to cause the brake control mechanism to controllably actuate brakes on vehicle wheels so as to maintain the slip rates of the wheels less than a predetermined limit. The slip control circuit is disabled, however, by a wheel liftoff detector circuit as the latter detects, when the vehicle is rounding a curve, the lifting of the inside wheels off the road surface. At the same time the wheel liftoff detector circuit causes a decrease in engine power through reduction of throttle opening, thereby minimizing the danger of vehicle turnover.

Abstract: A wheel slip responsive traction control system particularly well suited for use with a four wheel drive vehicle having a hydraulic brake control mechanism for individually controlling a fluid pressure acting on a brake on each drive wheel. The traction control system includes a drive mode selector which offers to the vehicle driver a choice among a "normal drive" mode, a "front drive" mode and a "rear drive" mode. When the driver chooses the "normal drive" mode, the control system controls the brakes on both front and rear pairs of drive wheels so as to maintain their slip rates at less than a relatively low first limit. When the "front drive" mode is chosen, the front pair of drive wheels are so braked as to maintain their slip rate at less than a second limit higher than the first limit. When the "rear drive" mode is chosen, the brakes on the rear pair of drive wheels are so controlled as to maintain the rear wheel slip rate at less than the second limit.