In the present study, A composite of polyester – fiber with the addition of rubber particles resulted from the recycling of wasted tires of railway vehicles, Coupled with the fast development of the automobile industry. The advantage of the developed product is being a solution for one of the most modern environmental challenges beside that it is economical and environment friendly. This developed composite can be used in many applications like car bodies specially in automotive bumper and in the aviation and marine industries. Different particles sizes range 20 mesh, 40 mesh, 1-3 mm and 3-5 mm were used in the present work to possess their variation effect on the mechanical behavior of the novel composite. Generally, addition of waste tire rubber led to decrease of tensile properties. This was accompanied with poor adhesion between waste tire rubber and polymer matrix at interface. It was observed that the size of waste tire rubber particles has an inversely relation to the tensile strength of the developed composite, Also the impact toughness shows better and tangible progress as the particles size increases till 40 mesh size then slightly decreases. All the mechanical testing were done according to ASTM standard