Disclosed is an intra-wheel rear suspension system moveably supporting a rotating wheel relative to a frame via a concentric hub structure, the system exhibiting minimal side play or torsional play due to its unique bearing structure. The system includes an inner carrier assembly having an inner slide block with front curved bearing surface and a rear curved bearing surface. A non-rotating axle extends to either side of the inner slide block and is secured to the frame. An outer track frame that is adapted for rotatably supporting the wheel via any suitable concentric hub structure, has a curved aperture with front and rear curved bearing surfaces that engage the front and rear curved bearing surfaces of the inner slide block. The outer track frame moves arcuately up and down relative to the inner slide block in response to a shock absorbing displacement. In order to minimize lateral side play or torsional movement, the outer track frame has left and right side bearing surfaces, and the inner carrier assembly has a pair of side plates fixedly secured to its left and rights sides, each side plate having a front and rear flat bearing surface that slidably engage the left and right side flat bearing surfaces of the outer track frame.