PURPOSE: To improve durability of a bead part by specifying a compound stiffener demarcation position and the ratio of a bead sectional area to a circumscribed contour sectional area of the tubeless captioned tyre and forming a carcass line of specified limits so as to be constant before and after replenishing the internal pressure.
CONSTITUTION: Before and after replenishment of the tyre internal pressure, thers shall be no substantial change of a carcass line between a point P2, at which a normal line L1 passing toward a carcass C through a point P1 where a face of contrary flexure of a flange Rf of a rim R separates from a bead part outside wall intersects the carcass C, and a point P3 on the carcass distanced from a bead base line L3 by 0.45 times as much as the largest vertical height H of a tyre. Further, the ratio of the total bead wire sectional area to the circumscribed contour figure sectional area of the bead core 4 is set above 0.82, and a demarcation between hard and soft parts of a compound stiffener 7 is set so as to pass between a point P4, where a rotary shaft parallel line L3 in contact with the bead core 4 sectional figure intersects a carcass rolling back 5", and the terminal P5 of the carcass rolling back 5". This configuration realizes improvement of durability of the bead part.
UEDA HIROSHI
KURIMA AKIRA
YAMAZAKI NAOKI
