Patent ID: 7905264
Filing Date: 2011-03-15
Classification: B60C

Abstract:
1. A pneumatic tire comprising a tread portion, a pair of axially spaced bead portions each with a bead core therein, a pair of sidewall portions extending between the tread edges and the bead portions, a carcass extending between the bead portions through the tread portion and sidewall portions, a belt disposed radially outside the carcass in the tread portion, a bead apex disposed in each said bead portions so as to extend radially outwardly from the radially outside of the bead core while tapering towards the radially outer end thereof, and a sidewall reinforcing rubber disposed axially inside the carcass in each said sidewall portion, wherein the sidewall reinforcing rubber extends radially outwardly and inwardly from a maximum section width position (m) of the carcass under a normally inflated unloaded state of the tire so as to have a radially outer end positioned axially inside an axial edge of the belt and beneath the belt, and a radially inner end positioned radially inside the radially outer end of the bead apex, but radially outside the bead core, and the axially inner surface of the sidewall reinforcing rubber is grooved so that the axially inner surface of each said sidewall portion is provided with a single groove opened toward the inside of the tire, and the groove extends circumferentially of the tire so that, when the tire mounted on a wheel rim and normally loaded is deflated, the groove in a ground contacting patch is closed, said groove is disposed at the substantially same radial position as said maximum section width position such that an axial straight line, which is drawn passing through the maximum section width position of the carcass, is positioned within a radial range from the radially outer edge to the radially inner edge of the groove, and the thickness of the sidewall reinforcing rubber is smoothly and continuously decreased from the grooved part to each of the radially outer end and inner end of the sidewall reinforcing rubber, the bottom of the groove is formed with a radius of curvature of not less than 1 mm but not more than 7 mm under the normally inflated unloaded state of the tire, the thickness of the sidewall reinforcing rubber at the bottom of the groove is not more than 8 mm but not less than 1 mm, the groove has an opening width in a range of not less than 3.0 mm, but not more than 15.0 mm, and a depth in a range of not less than 1.0 times, but not more than 5.0 times the opening width, wherein said groove has a wavy configuration or alternatively a zigzag configuration so that when the groove is closed in the ground contacting patch, the opposite walls of the groove can engage with each other.