PURPOSE: To perform level adjustment on a front wheel side and a rear wheel side at the same speed and at the same level with ease by setting the dia. of one free piston of a tube fitting on the connection side of a front-wheel-side jack unit larger than the dia. of the other free piston.

CONSTITUTION: A tube fitting connected to two front forks via a pipe has the half portion 60 provided with a coupling cylinder 62 as a cylindrical member which has an end piece 61 to thread a union bolt 55 thereto. In the coupling cylinder 62, a free piston 64 in which a recessed portion 63 is formed is slidably mounted via an O-ring 65 on the outer periphery. The dia. of the free piston 64 is set larger than the dia. of a free piston 104 at a tube fitting half portion 100 connected to two tube fitting half portions 60. In this way, the level raising speed of the front fork is slower and the level lowering speed of the front fork is faster.