A motor vehicle comprising: - a passenger compartment; - two side members comprising respective rear portions arranged longitudinally at said passenger compartment and respective struts, which project forward of said passenger compartment; - a crossbar with front attachment portions and rear attachment portions; - connecting devices (25,52), which fix said front and rear attachment portions to said side members in such a way as to keep said crossbar suspended in relation to said struts, and comprise at least one weakened zone designed to cause at least part of the crossbar to detach from the side members when a given load threshold is exceeded; at least one of said connecting devices (25,52) comprising: - a first wall (27,27a) having a first hole (29,29a) and forming part of said front or rear attachment portions; - a second wall (28,28a) having a second hole (30,30a) and forming part of said side members; - a bolt (26,26a) that comprises a threaded stem through said first and second hole and that is tightened to lock said first wall (27,27a) against said second wall (28, 28a); wherein said weakened zone comprises at least one slot (40,40a) cut in said first wall (27,27a) from an edge of said first hole (29,29a); said slot (40,40a) comprising an end zone defining a widening in relation to a remaining part of said slot (40,40a); said remaining part joining said end zone to said first hole (29, 29a); characterized in that said remaining part has a width, in circumferential direction, lower than the diameter of said threaded stem and said second wall is stiffer than said first wall (27,27a) so that, when said given load threshold is exceeded, said bolt (26,26a) is pulled by said second wall, deforms two rear flaps (45b,45c) of said first wall (27,27a) and slips out of a rear zone of said first hole (29,29a). - a passenger compartment; - two side members comprising respective rear portions arranged longitudinally at said passenger compartment and respective struts, which project forward of said passenger compartment; - a crossbar with front attachment portions and rear attachment portions; - connecting devices (25,52), which fix said front and rear attachment portions to said side members in such a way as to keep said crossbar suspended in relation to said struts, and comprise at least one weakened zone designed to cause at least part of the crossbar to detach from the side members when a given load threshold is exceeded; at least one of said connecting devices (25,52) comprising: - a first wall (27,27a) having a first hole (29,29a) and forming part of said front or rear attachment portions; - a second wall (28,28a) having a second hole (30,30a) and forming part of said side members; - a bolt (26,26a) that comprises a threaded stem through said first and second hole and that is tightened to lock said first wall (27,27a) against said second wall (28, 28a); - a first wall (27,27a) having a first hole (29,29a) and forming part of said front or rear attachment portions; - a second wall (28,28a) having a second hole (30,30a) and forming part of said side members; - a bolt (26,26a) that comprises a threaded stem through said first and second hole and that is tightened to lock said first wall (27,27a) against said second wall (28, 28a); wherein said weakened zone comprises at least one slot (40,40a) cut in said first wall (27,27a) from an edge of said first hole (29,29a); said slot (40,40a) comprising an end zone defining a widening in relation to a remaining part of said slot (40,40a); said remaining part joining said end zone to said first hole (29, 29a); characterized in that said remaining part has a width, in circumferential direction, lower than the diameter of said threaded stem and said second wall is stiffer than said first wall (27,27a) so that, when said given load threshold is exceeded, said bolt (26,26a) is pulled by said second wall, deforms two rear flaps (45b,45c) of said first wall (27,27a) and slips out of a rear zone of said first hole (29,29a).