PURPOSE: To restrict wandering at the time of running on tracks, and improve running safety by providing a base rubber layer between a belt layer in a corresponding zone to a circumferential row of blocks between main grooves in a wide tread and carcass, and forming swell in a belt layer part in contact with the base rubber layer.

CONSTITUTION: A studless tire 1 is provided with a cylindrical wide tread 4 which is lined with a belt layer 5 on a circumference of a crown part 3 of a radial carcass 2. This tread 4 comprises a block 9 having plural traverse sipes parted by at least a pair of main grooves 6 extended in the circumferential direction on both sides of a center circumferential surface 0, and a number of lateral grooves 7. A base rubber layer 11 is provided between the belt layer 5 and the carcass 2 at a corresponding zone to a circumferential row of blocks 91 between the main grooves 61 at least, a swell 12 is provided at a part of the belt layer 5 in contact with this base rubber layer 11, and the base rubber layer 11 is favorably of a width of 15-70% that of the belt layer 5.