Abstract: A frame having a U-shaped member which is placed over and around a leaf spring to be re-arched while still on a vehicle; a platform pivotally mounted on the U-shaped member, a hydraulic jack supported on the platform so that the ram or piston rod on the jack may be hydraulically forced against a bending member which comprises a pair of spaced spring contact members located on opposite sides of the U-shaped member and on the opposite side of the spring therefrom. The device may be assembled over a spring and hydraulic pressure applied to drive the contact members to create a bending moment about a round surface on the inside face of the top of the U-shaped member. The pressure may be reversed to de-arch the spring.