A v-ribbed belt manufactured in a molding or grinding process has in different areas of the structure thereof different elastomer materials. In upper rib segments oriented toward the belt pulley there is an elastomer material that is not electrically conductive. The lower rib segments are made of an electrically conductive elastomer material. The height ratio a/(a+b) of the height (a) of the lower rib segments to the overall height (a+b) of the rib, as measured at the material boundary located at the rib flank, is at least 6 percent, or the absolute height of the lower rib segments is at least 0.12 mm.

A v-ribbed belt manufactured in a molding or grinding process has in different areas of the structure thereof different elastomer materials. In upper rib segments oriented toward the belt pulley there is an elastomer material that is not electrically conductive. The lower rib segments are made of an electrically conductive elastomer material. The height ratio a/(a+b) of the height (a) of the lower rib segments to the overall height (a+b) of the rib, as measured at the material boundary located at the rib flank, is at least 6 percent, or the absolute height of the lower rib segments is at least 0.12 mm.

A friction transmission belt includes a compression layer forming a pulley contact portion, the compression layer includes an inner layer formed from a rubber composition and an outer layer provided on a pulley contact side of the inner layer and formed from a fiber member, and a ratio (M10 modulus/M50 modulus) of an modulus at 10% elongation in a belt longitudinal direction (M10 modulus) to an modulus at 50% elongation in the belt longitudinal direction (M50 modulus), of the rubber composition, is not less than 1.5.

A friction transmission belt includes a compression layer forming a pulley contact portion, the compression layer includes an inner layer formed from a rubber composition and an outer layer provided on a pulley contact side of the inner layer and formed from a fiber member, and a ratio (M10 modulus/M50 modulus) of an modulus at 10% elongation in a belt longitudinal direction (M10 modulus) to an modulus at 50% elongation in the belt longitudinal direction (M50 modulus), of the rubber composition, is not less than 1.5.

A rubber composition for a power-transmission belt includes: a polymer component including an ethylene--olefin elastomer; carbon black; and clay, in which the ethylene--olefin elastomer has a Mooney viscosity at 125 C. of 25 ML (1+4) 125 C. or less, the clay has a pH of 5.5 or higher, a total amount of the carbon black and the clay is 80 parts by mass to 180 parts by mass with respect to 100 parts by mass of the polymer component, and a mass ratio of the carbon black to the clay is clay/carbon black=0.2/1 to 1.2/1.

A rubber composition for a power-transmission belt includes: a polymer component including an ethylene--olefin elastomer; carbon black; and clay, in which the ethylene--olefin elastomer has a Mooney viscosity at 125 C. of 25 ML (1+4) 125 C. or less, the clay has a pH of 5.5 or higher, a total amount of the carbon black and the clay is 80 parts by mass to 180 parts by mass with respect to 100 parts by mass of the polymer component, and a mass ratio of the carbon black to the clay is clay/carbon black=0.2/1 to 1.2/1.