In the present study, a series of stress-controlled undrained cyclic torsional tests were performed to study the liquefaction resistance and equivalent shear modulus of sand–ground rubber mixture. By considering the mixture in which compressibility may be tolerable for geotechnical design (sand-like behaviour), four percentages of ground rubber (0, 5, 10, and 25%, by volume) were selected in the research. The tests were performed under three different confining pressures, at a constant relative density, and the effects of various parameters such as rubber fraction, and confining pressure were investigated. From the test results it is seen that the shear stiffness of sand decreases drastically, even when it is mixed with low percentages of the ground rubber. The liquefaction resistance of sand decreases by adding the ground rubber (up to 25% by volume) to it. The maximum and minimum decrease in the cyclic resistance ratio, caused by increasing the rubber fractions, occurred for corresponding confining pressures of 110 and 400 kPa, respectively. However, despite the large differences in the fraction of ground rubber in the soil, the liquefaction resistance of mixtures with 10 and 25% ground rubber is almost the same.