A wheelie control suspension system for snowmobiles is provided. The wheelie control suspension system may include at least one spring preload apparatus and at least one dampening apparatus. The wheelie control suspension system may operate to change the spring force or damping force of the front track shock and rear track shock at the switch of a knob or activation of an electronic button.

A wheelie control suspension system for snowmobiles is provided. The wheelie control suspension system may include at least one spring preload apparatus and at least one dampening apparatus. The wheelie control suspension system may operate to change the spring force or damping force of the front track shock and rear track shock at the switch of a knob or activation of an electronic button.

A damping force variable shock absorber includes a damping force variable mechanism including a damping force generator, a damping force variable actuator, and a damping force controller which controls an operation of the damping force variable actuator, and a vehicle height control mechanism including a self-pumping mechanism configured to, using a vibration caused by traveling of a vehicle as a driving force, pressurize a hydraulic oil and push a spring, a vehicle height variable actuator which switches a flow path of the hydraulic oil pressurize by self-pumping, and a vehicle height controller which controls an operation of the vehicle height variable actuator. The damping force controller performs a damping force variable control in which a damping force in a pushing process of the spring while a vehicle height is increasing is set to be weaker than a damping force during a period in which the vehicle height is not increasing.

A suspension device includes a spring, a jack, a reservoir chamber which reserves the oil, a first pump, a second pump an opening and closing unit. The second pump is configured to cause the oil to flow into the housing chamber and to cause the oil to flow out from the housing chamber.

A suspension device includes a spring, a jack, a reservoir chamber which reserves the oil, a first pump, a second pump an opening and closing unit. The second pump is configured to cause the oil to flow into the housing chamber and to cause the oil to flow out from the housing chamber.

An apparatus for adjusting vehicle height is disclosed. The apparatus for adjusting vehicle height, may include a pump configured to supply or recover a fluid; and an actuator mounted between a chassis and a vehicle body of a vehicle, the actuator being configured to receive the fluid from the pump to raise the vehicle body and increase the vehicle height, or to lower the vehicle body and decrease the vehicle height as the fluid is recovered by the pump.

Disclosed herein are various embodiments of a hydraulic actuator that includes one or more check valves having a dynamically varying cracking pressure. In certain embodiments, a hydraulic actuator may be configured to vary the cracking pressure of a check valve based on an operating condition of a pump of the hydraulic actuator. The check valve may be located along a bypass path in the hydraulic actuator, thereby allowing for fluid flow to bypass a pump of the hydraulic actuator by passing through the check valve. The use of such hydraulic actuators is contemplated in, for example, an active suspension system of a vehicle.

Additionally, various embodiments of suitable check valves are disclosed. Additionally, methods are disclosed for operation of the check valve and the hydraulic actuator.