SUSPENSION ARM SUPPORT STRUCTURE

PROBLEM TO BE SOLVED: To provide a suspension arm support structure that maintains predetermined strength of a shaft as well as ensures sufficient volume of a bushing both for sufficient damping performance. SOLUTION: A shaft 32 projecting from a lower arm is formed at its portion ranging from its base 32A to its axial substantially middle portion with an outside-diameter variable part 34 of outside diameters gradually and linearly reduced. A bushing 50 is formed at its inner cylinder 52 ranging from one end to the axial middle portion with an inside-diameter variable part 54 of inside diameters gradually reduced corresponding to the outside-diameter variable part 34. The reduced outside diameter of the inner cylinder 52 permits an increase in thickness of a rubber part 58 for increased elastic compliance, which effectively suppresses vibrations or thrust loads as compared with existing bushings. The portion of the shaft 32 nearer to the lower arm is thus reinforced with the outside-diameter variable part 34 for constant total strength of the shaft 32, which prevents the shaft 32 from breaking up or cracking even upon receiving shearing force applied as part of vibrations, thrust loads or longitudinal force.