Tread (1) of a tire for an off-road vehicle, with total width (W) and total thickness of wearable material at least equal to 60 mm. The tread is delimited axially by shoulder regions (5) provided with grooves (7). This tread (1) comprises, in central region (6), narrow groove (61) and, between each shoulder region (5) and the central region (6), an intermediate region (4) in which there are formed a plurality of oblique or transverse narrow grooves (411, 412). Narrow groove (61) of the central part is made up of first narrow-groove parts (611) of depth (P1) and of second narrow-groove parts (612) of depth (P2). Depth (P1) is greater than depth (P2). Narrow grooves (411, 412) of one same intermediate region comprise, in the circumferential direction, an alternation of narrow grooves (411) of first depth (P11) and of narrow grooves (412) of second depth (P22).