Abstarct: The broken down tires of old cars are recognized as one of the most important industrial waste and factory waste that has been increased rapidly and as a result ,many problems have been appeared for human societies.in recent decades, Recycling of this material has been considered in other industries, especially civil engineering. In recent years, researchers have examined the possibility of using this material in concrete, soil and asphalt mixtures and have shown that the combination of this material with these materials improves some of their properties. in this issue we are about to examine the possibility of replacing rubber substitutes, instead of a part of the rock materials in the baxse laxyer of road and studying its effects on this laxyer. So, , CBR and PFWD tests have been carried out. and their results are two important factors in the design and control of road pavement quality. In this study, sub-particles with 9.5 to 4.75mm in size were used as substituting materials which¬ includes sieves between4and3/8. The results of the CBR test in dry state showed that, with the replacement of 20, 40 and 60 percent of the crumb rubber with a part of the portion of bedding of rocky material from baxse laxyer of the road, the amount of CBR of the samples increases, moreover in saturated CBR by replacing the crude rubber with sieve which is number 4 Increases. But by the replacing crumb rubber with sieve which is number 3/8 in size it decreases. The results of the PFWD test showed that the increase in the elastic modulus was 3.2%, 10.1% and 12% respectivly for samples containing crumb rubber are 20%, 40% and 60% respectivly with sieve which its number 4, and this increase for the sample The crude rubber containing 20, 40 and 60% respectivly and with sieve which its size is 3/8 are 5.8, 18.4 and 24.9%. The increase of this parameter in the baxse laxyer of the soil caused the decrease of slurry and cracks or reduces the severity of these damages. According to the Statsqui loading test, it can be said that with the addition of sub-tires, the load capacity has decreased, and this decrease is directly related to the amount and size of the sub-rubber substitute. As with the increase in the percentage of the crumb rubber, the capacity of the load decreases and with the increase in size, the same trend can be observed