This work sought to understand race, gender, income, and housing inequalities of users of bike--sharing systems in the cities of São Paulo and Rio de Janeiro. A face-to-face sample survey was carried out and the obtained data were compared with data from the two cities concerning the above-mentioned social markers. The results show that the systems are more accessible to some groups, such as women and black people, and less accessible to others, such as low-income people, and that, despite being in urban centers, they manage to maintain the inclusion of groups that do not live in the region. Based on the results, the insertion of these systems in Brazilian cities is discussed.