HYDRAULIC SUSPENSION OPERATION
SPRUNG/UNSPRUNG Circuit The key to the operation of the M9 ACE is its hydropneumatic suspension
system that allows the vehicle to operate in both SPRUNG and UNSPRUNG modes.
SPRUNG Mode Pressure is delivered through line 9 to bump stops and front actuator fill valves, causing
the bump stops to extend and limit movement of the front roadwheel arms. The actuators become a fixed
suspension with the accumulators acting like shock absorbers for the system, providing a smooth ride up to
30 MPH (48 Km/H). SPRUNG mode is used for road marches and parking.
UNSPRUNG Mode Pressure is routed through the SPRUNG/UNSPRUNG valve to line 11 and to the
actuator wheel valves, causing bump stops to retract and the suspension system to become variable. The
front of the vehicle can be raised or lowered, and the operator has independent control of the left and right
suspension components. UNSPRUNG mode is used for earthmoving operations.
SPRUNG/UNSPRUNG CONTROL VALVE Located to the right of the main valve bank, facing rearward, this valve
regulates fluid flow for whichever mode is selected.