Abstract: Piston rod assembly includes a piston head and rod which are formed separately and subsequently jointed together by injecting adhesive through a porting passage in the piston head into an annular space formed by an internal groove in the piston head and an external surface of the rod to provide a bonded joint therebetween. The piston head includes a radially enlarged center dam portion and a pair of reduced diameter end portions extending coaxially from opposite sides of the center dam portion. The internal groove extends axially beyond opposite sides of the center dam portion for a substantial portion of the length of the reduced diameter end portions. The reduced diameter end portions are externally tapered radially inwardly from opposite sides of the enlarged center dam portion toward opposite ends of the reduced diameter end portions to provide a gradual build-up of stiffness in the piston head from the opposite ends of the bonded joint toward the middle.