An undercarriage for a vehicle including at least two longitudinal beams, at least one transverse beam and at least one wheel axle. The height of the foremost part of the longitudinal beams has a reduction in height that defines a swan-neck. The longitudinal beams are made of a composite material including a thermoplastic synthetic material with reinforcing fibers. The height of the foremost part of the longitudinal beams is reduced by means of plastic deformation.