A hub-axle assembly (10) and lubrication system thereof includes a spindle (11) having an inner end (12) and outer end (15) with inner (13) and outer (14) bearing assemblies spaced axially on the spindle (11). A hub body (16) is rotatably supported on the bearing assemblies (13, 14) and has a wheel mounting flange (17) extending radially outward therefrom. Lug bolts (18) extend axially outward from the flange (17) with one such lug bolt (18) having an axial bore (24) therein. Grease applied at a grease fitting (23) in the axial bore (24) is transmitted to a lubrication chamber (19) within the hub body (16) via tubing (25) to lubricate the lubrication chamber (19). A circumferential recess (27) in the hub body (16) has at least one aperture (28) therein which is normally closed by an O-ring (29) positioned in the recess (27). However, when the pressure of the grease within the hub body (16) is sufficient to indicate that the lubrication chamber (19) has been lubricated, the O-ring (29) will expand causing grease to flow through the aperture (28).