Patent ID: 8656970
Filing Date: 2014-02-25
Classification: B60C

Abstract:
1. A pneumatic radial tire for a motorcycle in which a directional pattern composed of two groups of tilt lug grooves is formed on a tread face portion, characterized in that: (a) said tilt lug grooves are disposed at a tilt angle of 5 to 85° with respect to a circumferential direction of the tire; and (b) said tilt lug grooves are formed so that a ratio Lmin/W of their minimum length Lmin to a surface length W along one side of the tread from the equator of the tire to the edge of the tread is 0.1 or higher in a no-load state in which the tire is mounted to a standard rim and air is filled to a standard internal pressure; (c) said two groups of the tilt lug grooves are each formed of two or more pairs of tilt lug grooves; (d) said two groups of the tilt lug grooves are formed of a first group of tilt lug grooves (G (e) said G wherein: a ratio Lmax/W of a maximum length Lmax of the tilt lug groove within said respective groups of tilt lug grooves to the surface length W along one side of the tread from the equator of the tire to the edge of the tread meets 0.4≦Lmax/W≦2.0 in the no-load state in which the tire is mounted to the standard rim and air is filled to the standard internal pressure, a ratio Lmin/W of a minimum length Lmin of the tilt lug groove within said respective groups of tilt lug grooves to the surface length W along one side of the tread from the equator of the tire to the edge of the tread meets 0.1≦Lmin/W≦1.0, two or more tilt lug grooves having the maximum length Lmax and the lug grooves having the minimum length Lmin exist within each group of tilt lug grooves, pitches of said first group of tilt lug grooves are one-third to 1/12 of an entire circumferential length of the tire tread, pitches of said second group of tilt lug grooves are one-third to 1/12 of an entire circumferential length of the tire tread, and said first group of tilt lug grooves and said second group of tilt lug grooves are disposed so that at least one tilt lug groove of said first group on the right side of the tread face portion connects with at least one tilt lug groove of said second group on the right side of the tread face portion, at least one tilt lug groove of said first group on the left side of the tread face portion connects with at least one tilt lug groove of said second group on the left side of the tread face portion, at least two tilt lug grooves of said first group on the left side of the tread face portion do not connect with any one of the tilt lug grooves of said second group on the left side of the tread face portion, and at least two tilt lug grooves of said second group on the right side of the tread face portion do not connect with any one of the tilt lug grooves of said first group on the right side of the tread face portion.