Self-sealing tire

In a tube (2) whose internal space is partitioned by a partition wall to formed an air (3) chamber filled with air and a sealant chamber (7) filled with a sealant (8), the ratio R (R = B/A) of a sectional area B of a contour of the tube accommodated in the tire (1) and expanded by filling of air to a sectional area A of a contour of the tube in an unexpanded is set in a range of 100% to 110%. Thus, the tension of the partition wall at the time when the tube has been expanded is suppressed to a small extent. Even if the partition wall of the tube gets a punctured wound, the partition wall having only a small tension applied thereto has a weak tendency to be intended to be contracted toward the air chamber. Therefore, the air in the air chamber little flows into the sealant chamber and thus, a reduction in sealing performance of the sealant due to the mixture with the air is prevented.