Patent ID: 7360569
Filing Date: 2008-04-22
Classification: B60C,Y10S

Abstract:
1. A pneumatic tire provided with four main grooves on a tread grounding surface that extend in a successive manner in a tire circumferential direction, wherein the main grooves are comprised of one large width main groove, the groove width thereof being in the range of 4 to 20% of a tread grounding width and the groove center thereof being spaced from a tire equator by a distance of 5 to 30% of the tread grounding width to one grounding end side in an tire axial direction, and small width grooves that are disposed between the large width main groove and the other grounding end and which groove width is larger than 2.0 mm but smaller than that of the large width main groove, and wherein both groove side edges of the large width main groove extend in a successive and linear manner in the tire circumferential direction without being interrupted by lateral grooves, sipings, slots or other notches, wherein a ratio ST/SY between an front and rear rigidity ST of the tread grounding surface in the tire circumferential direction on average of a single round of the tire and a lateral rigidity SY in the tire axial direction is set to be larger than 0.9 but smaller than 1.1, wherein the tread grounding surface is partitioned into a first shoulder block region between the large width main groove and the one grounding end, a first crown block region between the large width main groove and a first small width main groove that adjoins the large width main groove on the other grounding end side, a second circumferential rib region between the first small width main groove and a second small width main groove adjoining the first small width main groove on the other grounding end side, a third crown block region between the second small width main groove and a third small width main groove adjoining the second small width main groove on the other grounding end side, and a second shoulder block region between the third small width main groove and the other grounding end, wherein the lateral rigidity SYs is set to be larger than the front and rear rigidity STs for the first shoulder block region and the second shoulder block region, and the lateral rigidity SYc is set to be smaller than the front and rear rigidity STc for the second circumferential rib region, wherein the groove width of the third small width main groove is larger than the groove width of the first and second small width main grooves, and wherein each block regions and rib region comprise sipings, and an edge component lengths LE in a tire axial direction of all edges including edges of those sipings and edges of the blocks satisfy