Automobile suspension part

An automobile suspension part comprising

• an arm member in a groove shape and a reinforcement in a plate shape, wherein:
• the arm member comprises a top wall part, a first ridge line part, a second ridge line part, a first side wall part, and a second side wall part;
• the top wall part comprises a first attachment part at a first end part;
• the top wall part comprises a second attachment part at a second end part;
• the first ridge line part is sandwiched between the top wall part and the first side wall part;
• the second ridge line part is sandwiched between the top wall part and the second side wall part;
• the first ridge line part and the second ridge line part extend along an extending direction of the top wall part;
• the reinforcement comprises a bottom wall part, a third ridge line part, and a flange part;
• the third ridge line part is sandwiched between the bottom wall part and the flange part;
• the bottom wall part is joined to the first side wall part and the second side wall part;
• a transverse cross-section of the automobile suspension part comprising the arm member and the reinforcement is a closed cross-section;
• the third ridge line part is connected to the first side wall part and the second side wall part;
• the flange part is joined to the top wall part between the first attachment part and the second attachment part;
• and
• the flange part is connected to the first side wall part and the second side wall part.