| 摘要 |
A pneumatic radial tyre having a tread (2) provided with four main grooves (G1,G2) extending continuously in the circumferential direction of the tyre arranged symmetrically with respect to the tyre equator so as to divide the tread (2) into five ribs (RC,RM and RS), the four main grooves (G1,G2) consisting of a pair of axially inner main grooves (G2) disposed one on each side of the tyre equator (CO) and a pair of axially outermost main grooves (G1) disposed one between each tread edge (TE) and each inner main groove (G1) characterised in that each shoulder rib (RS) between the outermost main groove (G1) and the tread edge (TE) is provided with shoulder lateral grooves (g1L, g1R) extending from the outermost main grooves to the tread edge so as to divide the shoulder rib (RS) into blocks, each middle rib (RM) between the inner main groove (G2) and the outermost main groove (G2) is provided with middle lateral grooves (g2L, g2R) extending from the inner main groove (G2) to the outermost main groove (G1) so as to divide the middle rib (RM) into blocks, and the central rib (RC) between the two inner main grooves (G2) is provided with central lateral grooves (g3L, g3R) extending from the inner main grooves (G2) towards the tyre equator (CO) and terminated in the central rib (RC) so as to provide continuity in the circumferential direction (D) of the tyre, wherein in the state where the tyre is mounted on its regular rim and inflated to its regular inner pressure and loaded with its regular tyre load, the quotient (WG/W) of the total (WG) of the axial widths (WG1, WG2) of the four main grooves (G1 and G2) divided by the ground contact width (W) measured between the axial edges (SE) of the ground contacting area (S) being in the range of 0.25 to 0.32, and on each side of the tyre equator, the ground contact width (W) and the total (LG1+LG2) of the axial length (LG1) measured from the ground contacting area edge (SE) to the axially inner edge of the shoulder rib (RS) and the axial length (LG2) measured from the ground contacting area edge (SE) to the axially inner edge of the middle rib (RM) satisfying the relation: <MATH> <IMAGE> |
