PURPOSE: To facilitate changing of rate of axles weight to two kinds for a steering axle by a method wherein a cylinder is arranged between a beam for supporting the steering axle and a chassis in the large-sized vehicle having three adjoining axles in which one of them is made to be a single wheel steering axle.

CONSTITUTION: Double wheel tyres 10 and 11 are mounted on the axles 7 and 8 of the large-sized construction vehicle e.g. rear axle 7W9 as nonsteering axles, the axle 9 has a single wheel tyre 12 as the steering axle. At the lower part of the chassis 1 a pair of right and left balancing beams composed of three boggie beams 13W15 of front, central and rear parts. Each of the beams 13 and 15 is pivotally supported at the lower surface of the chassis frame 2, the beam 14 is pivotally supported at the lower surface of the central axle 8 via brackets 16 and 18 at each of the intermediate portions thereof, one end of the beams 13 and 15 is pivotally supported on the beam 14. Then the hydraulic cylinder 33 is arranged between the beam 15 and the chassis frame 2, the ratio of axle weight for the steering wheel axle may be changed under an action of the cylinder.