Abstract: A caster angle regulating tool for automobile wheels includes a prismatic head (15), a set of wheel drum plate mounting disks (18, 19, 20) interchangeably attachable by screws (25) in holes (23) therethrough to screw threaded bores (17) in bosses (16) on the prismatic head (15), a pivotable adjusting nut (11) pivotly mounted by opposite axle shafts (12) thereon in bearings (13) in brackets (14) mounted on the prismatic head, a screw threaded adjusting shaft (6) engageable in the adjusting nut (11) and a clamping device (1, 2, 3, 4) rotatably mounted on one end (5) of the adjusting screw for clamping onto a stub axle (M) attached to the wheel drum plate (R). Rotation of the adjusting shaft (6) in the adjusting nut (11) thereby moves the spring stub axle to increase or decrease the caster angle, depending upon the direction of rotation of the adjusting shaft during alignment of the wheels.