AST BMW G83 M4 Cabriolet xDrive Lowering SpringsGive your BMW G83 M4 Cabriolet the extra stance it needs with AST lowering springs. AST Lowering Springs are manufactured from a premium high tensile chromium silicone wire which is handpicked by AST engineers for its quality and metal consistency. Each spring is cold wound and then heat treated to increase hardness and reduce internal stresses present after winding. Each spring is then individually shot peened, phosphate treated, and then powder