Structure of suspension mounting portion and assembling method thereof

A structure of a suspension mounting portion comprising:

• a side member extending in a longitudinal direction of a vehicle and connected to a lower surface of a floor panel;
• a closed cross sectional portion formed by use of the floor panel and the side member;
• a suspension bolt mounting a suspension system constituting element to a lower side of the closed cross sectional portion;
• a first mounting surface provide by use of a recess portion formed on a bottom wall of the side member so as to mount the suspension bolt;
• a reinforce provided to an inner portion of the closed cross sectional portion;
• a second mounting surface provided to the reinforce and having a convex portion so as to mount the suspension bolt, the convex portion protruding in an upward direction of the vehicle and having a substantially circular cross section taken along a horizontal plane of the vehicle,
• wherein the suspension system constituting element is mounted to the lower side of the closed cross sectional portion by use of the suspension bolt fixed through the first mounting surface and the second mounting surface.