Abstract: A rotary mower (22) having an improved castering wheel assembly (39, 92) so as to reduce rotation of the castering wheel (4) about its support shaft (6). In one embodiment, a torsion resistance mechanism (2) is interposed between the shaft (3) and mower frame (67), the torsion resistance mechanism (2) including a resilient material (46) rigidly bonded to a sleeve (77) in which the shaft (3) is retained. The resilient material (46) is press fit into a housing (11), the housing (11) being rigidly bonded to the mower frame (67). In another embodiment, a cap (98) housing a spring (102) is threadably attached to the castering wheel support shaft (81). Rotation of the cap (98) compresses spacers (85-90) mounted co-axially on the shaft (81) while urging the shaft (81) in an upward direction (111) so as to prevent axial rotation of the shaft (81) when the castering wheel loses contact with the ground.