A high load capacity journal foil bearing and more particularly undersprings therefor. The journal foil bearing preferably includes a number of individual pads or foils which are conventionally mounted to a journal and have a pad face proximate a rotating shaft. The undersprings each include a number of curvilinear support beams or corrugations which are varied in width and pitch to optimize the spring force supporting the overlying foil. The underspring is configured to have wider beams at their leading edge and progressively narrower beams for approximately the first one half of the circumferential length.