A ground-engaging track system comprising: a track including a first track chain, a second track chain, and a plurality of track pins coupling the first track chain to the second track chain; an idler structured for mounting to a track roller frame, and including an idler body defining an axis of rotation, and an outer idler rim extending circumferentially around the axis of rotation; the first track chain and the second track chain each including track links (36, 38) in an end-to-end arrangement and including, respectively, a first track rail and a second track rail; the track links (36, 38) in the first track chain and the second track chain each including a lower shoe-mounting surface, an upper rail surface (46, 47) forming a segment of the respective first track rail and second track rail, and an inboard link body side; and the track links (36, 38) in the first track chain and the second track chain each further including an inboard rail protrusion (48, 49) extending from the inboard link body side, and the upper rail surfaces (46, 47) each including an anti-scalloping bump-out (50, 51) formed upon the respective inboard rail protrusion (48, 49); characterised in that the outer idler rim includes a central flange, and a first set of pockets and a second set of pockets are formed in the central flange and arranged, respectively, in rolling register with the inboard rail protrusions (48, 49) of the track links (36, 38) in the first track chain and the second track chain; the outer idler rim includes a first rail contact surface, and a second rail contact surface; and the first set of pockets and the second set of pockets are formed in the central flange adjacent, respectively, to the first rail contact surface and the second rail contact surface. a track including a first track chain, a second track chain, and a plurality of track pins coupling the first track chain to the second track chain; an idler structured for mounting to a track roller frame, and including an idler body defining an axis of rotation, and an outer idler rim extending circumferentially around the axis of rotation; the first track chain and the second track chain each including track links (36, 38) in an end-to-end arrangement and including, respectively, a first track rail and a second track rail; the track links (36, 38) in the first track chain and the second track chain each including a lower shoe-mounting surface, an upper rail surface (46, 47) forming a segment of the respective first track rail and second track rail, and an inboard link body side; and the track links (36, 38) in the first track chain and the second track chain each further including an inboard rail protrusion (48, 49) extending from the inboard link body side, and the upper rail surfaces (46, 47) each including an anti-scalloping bump-out (50, 51) formed upon the respective inboard rail protrusion (48, 49); characterised in that the outer idler rim includes a central flange, and a first set of pockets and a second set of pockets are formed in the central flange and arranged, respectively, in rolling register with the inboard rail protrusions (48, 49) of the track links (36, 38) in the first track chain and the second track chain; the outer idler rim includes a first rail contact surface, and a second rail contact surface; and the first set of pockets and the second set of pockets are formed in the central flange adjacent, respectively, to the first rail contact surface and the second rail contact surface.