Abstract: The load supported and transferred by the rear auxiliary axle of a truck is commonly determined by the fluid pressure supportively disposed between the auxiliary axle and the rear end of the truck frame. Where the auxiliary axle is some distance to the rear of the truck for that purpose, the wheels are castered to avoid scuffing. The castering, however, must generally be damped to avoid fluttering of the wheels and shimmying of the axle. Frictional damping means which is here disclosed is both adjustable and varied automatically with the amount of such pressure and the amount of load transferred. In particular the stability of the vehicle is greatly improved.