Patent ID: 6705367
Filing Date: 2004-03-16
Classification: B60C

Abstract:
A heavy duty pneumatic radial tire comprising: a tread portion a lug pattern formed on both sides of said tread portion, lug grooves forming lugs extending from a position separated from an equatorial plane of the tire by a width L0 corresponding to 3-15% of a ground contact width up to each of both ends of the tread portion and opened at a tread end, each of said lug grooves having two separated platforms each raised from a bottom of the lug groove, one platform being located at a top end portion near the equatorial plane and a second platform being located at a central portion in a longitudinal direction of the lug groove and separated from said first platform, and said platforms have a surface shape such that a depth of the lug groove at the top end portion is shallower than a groove depth at the central portion, each platform extending across the entire width of the lug groove,wherein the one platform is existent in such a place that a ratio L1/L, where L1 is a distance on a vertical line drawn from the position of the top end of the lug groove to an end of the one platform and L is a vertical distance ranging from the position of the top end of the lug groove to the tread end corresponding to an end of a ground contact width in a ground contact face of the tread portion, is within a range of 0.1-0.2 and satisfies such a condition that a ratio h1/H1, where h1 is a height of the platform from a bottom line of the lug groove and H1 is a height from the bottom line to the ground contact face on a normal line drawn to the ground contact face, is within a range of 0.2-0.6; and wherein the second platform is existent in such a place that a ratio L2/L, where L2 is a distance on a vertical line drawn from the position of the top end of the lug groove to a terminal end of the second platform and L is a vertical distance ranging from the position of the top end of the lug groove to the tread end corresponding to an end of a ground contact width in a ground contact face of the tread portion, is within a range of 0.2-0.5 and satisfies such a condition that a ratio h2/H2, where h2 is a height of the second platform from a bottom line of the lug groove and H2 is a height from the bottom line to the ground contact face on a normal line drawn to the ground contact face, is within a range of 0.1-0.4.