Abstract: An axle/suspension system (1) has an axle (5) supported from the frame of the vehicle by a pair of rigid longitudinal beams (4) pivoted to frame hangers (3). Air springs (7) and shock absorbers (8) connect between the rigid beams (4) and the frame above to control suspension movement. The axle/suspension system is particularly suited as a mid-lift axle on the tractor of a tractor-trailer vehicle. A characteristic feature is the pivotal connection (21) between each hanger (3) and beam (4), which is through a resilient bush (6) having a compliance ratio—being a ratio of the longitudinal spring rate to the vertical spring rate—of at least 10:1.

Abstract: An axle/suspension system (1) has an axle (5) supported from the frame of the vehicle by a pair of rigid longitudinal beams (4) pivoted to frame hangers (3). Air springs (7) and shock absorbers (8) connect between the rigid beams (4) and the frame above to control suspension movement. The axle/suspension system is particularly suited as a mid-lift axle on the tractor of a tractor-trailer vehicle. A characteristic feature is the pivotal connection (21) between each hanger (3) and beam (4), which is through a resilient bush (6) having a compliance ratio—being a ratio of the longitudinal spring rate to the vertical spring rate—of at least 10:1.