A tire includes a tread profile and a plurality of ribs extending across the tread profile. Each rib includes a first portion and a second portion on two sides of the center axis of the tread profile. The first portion includes a first section which has a constant height. The length of the first section is “L1”. A first shoulder is connected between the first section and the outer side of the tire by a first radius. “R1”. The second portion includes a second section which has the same constant height as the first section. The length of the second section is “L2”. A second shoulder is connected between the second section and the inner side of the tire by a second radius “R1”. A ratio of the “L1” to the “L2” is 1.1 to 1.4, and a ratio of the “R1” to “R2” is 0.5 to 0.9.