Systems and methods for using a brake system to selectively lock and release the vertical motion of a C-arm X-ray device that is part of a sliding counterbalanced C-arm positioning device are described. In such systems and methods, the C-arm positioning device typically includes a C-arm X-ray device, a linear bearing rail assembly, a linear bearing block, a counterbalance mechanism, and brake system. Generally, the C-arm is connected to the linear bearing block, which is slidably coupled to the bearing rail assembly to allow the bearing block and C-arm to slide up and down on the rail assembly. The counterbalance mechanism applies a force to the bearing block to substantially counterbalance the weight of the components, such as the C-arm, that are suspended from the bearing block. The brake system can be actuated to engage the linear bearing rail assembly and lock the vertical movement of the linear bearing block. Other embodiments are described.