This paper presents the research on recycled rubber material design, made from vehicle tires, to be used as a matrix of low-cost seismic isolators' prototypes for risk mitigation in South America buildings.Four mixes were contrasting to determine the influence of the particle size distribution on the recycled rubber characteristics, three of them with different size particle composition and the last one with a non-control distribution.Mechanical properties such as density, hardness, and tensile stress, were studied, and stereoscopic images were taken.In the controlled size distribution case, the experimental results showed an improvement in the packing capacity of the particles with a better consolidation of the material under the same processing conditions as a consequence.Regarding the tension stress, the controlled mixes achieved a maximum strength higher than the non-controlled mix (up to 70%), and their spectroscopy images show consolidated materials without voids or pores.All the samples presented a similar hardness with values higher than the natural rubber one (60).Therefore, the development of recycled rubber material with a control size distribution allowed to improve the material behavior without changes in the manufactured process.