In this paper we propose a tank-like climbing robot, called Tankbot, using flat (non-patterned) and soft elastomer adhesive treads. This wheeled climbing robot design enables continuous, vibration-free, and strong attachment to wide range of smooth and rough surfaces, relatively fast and smooth motion, and improved capability to traverse obstacles and to carry high payloads. Tankbot is lightweight (60-150 g) and can climb on any slope from 0 degrees to 360 degrees on smooth surfaces. Moreover, climbing vertically up, down, and laterally on relatively rough surfaces, such as a wooden door, a painted wall, and a brick wall, is also possible. A passive or active tail is added to Tankbot to transfer the peeling force to the front wheel and to assist for transitioning to different surface slopes. It is shown that the normal component of the peeling force with respect to the surface is crucial and has to be maximized to maximize the climbing stability. Moreover, it is demonstrated that the tread tension should be in a specific range to maximize the normal peeling force. With the aid of the derived models, different Tankbot prototypes with different body and tread dimensions are manufactured and tested for different tasks. It is shown that a 115 g Tankbot can carry up to 300 g on a regular painted wall. Tankbot can go over obstacles of up to 16 mm in diameter, perform both internal and external vertical wall to ceiling transitions, steer in two dimensions with a minimum turning diameter of 80 cm, and loiter on painted walls for up to 5 min.