When the tread portion generates heat during rotation of the tire with a load applied thereon, the temperature of the tread portion rises, causing various failures such as heat separation of the tread portion and the like. Therefore, in order to lower the temperature of the tread portion, it is necessary to reduce the heat generation or to promote heat dissipation.
Conventionally, in order to lower the temperature of the tread portion, there has been employed a method of forming grooves in the tread portion by removing tread rubber that serves as a heat source and, simultaneously, increasing a surface area of the tread portion such that the heat dissipation is enhanced (For example, Patent Document 1).