Abstract: An apparatus for use in self-sealing treatment of tubeless tires includes a frame, first and second rotatable tire orienting members movably supported on the frame, a threaded rod assembly, located on the frame, for moving the first and second members on the frame and a motor connected by a transmission assembly, adjustable by a pulley, to the first member for driving that member. The apparatus further includes in upstanding assembly connected to the frame, and an adjustment device including a piston for moving a third rotatable tire orienting member on the upstanding assembly. Each of the rotatable members has a body including two opposing frustum-like portions having an axis of rotation therethrough. The rotational axis of each rotatable member is parallel to those of the other two members. Also disclosed is a sealing composition including an elastomeric contact adhesive and fragmentatious sealing matter which makes up from 5 to 50% of the total volume of the composition.