PURPOSE: To accurately transmit steering motion to the front wheel without play by making coaction of a guiding means by a single supporting arm extending along only on one side of the front wheel and a guiding means by a shift arm provided rotatably on the front wheel axle

CONSTITUTION: A supporting arm 1, which extends along one side of the front wheel and is connected to a ball head of the motorcycle, includes a pair of V shape sectioned straight guiding grooves 4, 5 extending symmetrically to the front wheel axle 6. A shift piece 2, which is rotatably mounted on the front wheel axle 6 through a front wheel bearing, is formed with a pair of V shape sectioned guiding grooves 12, 13 symmetry to the axle 6 so that it may coact with the guiding grooves 4, 5 on the supporting arm 1. An impact dumper 18, which is arranged in a chamber 17 of the supporting arm 1, has its one side connected with the supporting arm 1 and the other side connected with a shift piece 2. By coaction of the guiding grooves 4, 5, 12, 13 thus formed, steering motion is accurately transmitted to the front wheel.