1. Field of the Invention
The present invention relates to a pneumatic tire, particularly to a high or ultra high performance pneumatic tire, having an asymmetric tread profile.
2. Description of the Related Art
A pneumatic tire generally comprises: a torodial carcass structure comprising at least one carcass ply; a tread band in a position radially external to the carcass structure; a belt structure interposed between the carcass structure and the tread band; a pair of sidewalls applied to the carcass structure in axially opposite positions. The ends of the at least one carcass ply are associated to respective annular reinforcing elements so as to form tire beads, which secure the tire to a wheel rim.
Generally, a tire has a symmetric tread profile, i.e. the tread profile, considered in a cross-section lying on a tire radial plane, has a symmetric shape with respect to the equatorial plane of the tire. To improve performance of tires to be used in high-powered cars, particularly during cornering at high speeds, asymmetric tread profiles have been proposed in the art.
For instance, EP 0 755 808 B1 discloses a pneumatic tire comprising a carcass extending around the tire from bead to bead, sidewalls and a rubber tread region which has a profile when considered in transverse cross section of a new tire terminating the sides of the tread in inner and outer shoulder regions respectively, each said shoulder region having a shoulder drop, which is the distance in the radially inward direction from the point of maximum tire diameter to a shoulder point at the edge of the shoulder region, characterized in that when the tire is mounted on a scheduled wheel rim and inflated to a scheduled pressure, the tread region is asymmetric having its said point of maximum tire diameter offset in the axial direction of the tire from the center line of the tire section in the direction of the inner shoulder, and the shoulder drop of the outer shoulder is greater than the shoulder drop of the inner shoulder such that the tread region has an asymmetrical profile.
EP 0 820 884 B1 discloses a pneumatic radial tire comprising a carcass extending around the tire from bead to bead, sidewalls and a rubber tread region which has a profile when considered in transverse cross section of a new tire terminating at the sides of the tread in inner and outer shoulder regions respectively, each said shoulder region having a shoulder drop, which is the distance in the radially inward direction from the point of maximum tire diameter to a shoulder point at the edge of the shoulder region, such that when the tire is mounted on a scheduled wheel rim and inflated to a scheduled pressure, the tread region is asymmetric having its said point of maximum tire diameter offset in the axial direction of the tire from the center line of the tire section in the direction of the inner shoulder, and the shoulder drop of the outer shoulder is greater than the shoulder drop of the inner shoulder such that the tread region has an asymmetrical profile, characterized by the tread region having substantially constant tread gauge or thickness except at the inner shoulder which has a locally reduced tread gauge or thickness so that the inner shoulder profile is trimmed.
US 2003/0121582 A1 discloses a pneumatic radial tire having a tire meridian cross-sectional configuration of a tread surface portion on at least one side of the tire center line which is arranged such that, when a position A is an intersection of the tire center line and the tread surface, and when a position B is an intersection of a straight line P drawn orthogonal to the tire axis from an edge of an innermost belt layer and the tread surface, an angle α between a straight line X connecting the positions A and B and a straight line Y drawn perpendicular to the tire center line from the position A is set in a range of 8 to 10 degrees, when the pneumatic radial tire is attached to a standard rim specified in JATMA with its air pressure being 180 kPa and with no load applied thereto.