there is provided an improved coiled tubing injector for injecting and withdrawing a length of flexible , cylindrical tubing into and from a well bore . the improved injector comprises first and second sets of gripper shoes , and drive mechanism for moving the sets of gripper shoes around first and second endless paths , respectively . the endless paths include parallel sections disposed on opposite sides of a length of the tubing . within these parallel sections , the gripper shoes are pressed against the tubing with sufficient force to hold the tubing therebetween . each gripper shoe includes a base portion connected to the drive mechanism and at least two substantially nondeformable gripper elements , each having cylindrical gripping surfaces corresponding to the outer surface of the tubing . a body of elastomeric material connects the gripper elements to the base portion and permits movement of the gripper elements between open and closed positions .