Fixed-type constant velocity universal joint

A fixed constant velocity universal joint, comprising:

• an outer joint member having an inner surface provided with track grooves;
• an inner joint member having an outer surface provided with track grooves paired with the track grooves of the outer joint member;
• a plurality of balls for transmitting torque, the plurality of balls being interposed between the track grooves of the outer joint member and the track grooves of the inner joint member;
• and
• a cage for holding the plurality of balls, the cage being interposed between the inner surface of the outer joint member and the outer surface of the inner joint member,
• the fixed constant velocity universal joint comprising a lubricating grease sealed therein,
• wherein the plurality of balls comprises eight balls,
• wherein a spherical angle of the outer joint member is within a range from 17° to 18.5°,
• wherein the outer joint member comprises a spherical inlet provided with cut out portions for incorporation of the cage,
• wherein a surface roughness of each of the plurality of balls is Ra 0.15 μm or less,
• wherein a surface roughness of a counterpart surface on which a corresponding one of the plurality of balls rolls is within a range from Ra 0.4 μm to Ra 1.8 μm so as to be higher than the surface roughness of each of the plurality of balls, and
• wherein an additive composition of the lubricating grease comprises a base oil, a diurea compound, molybdenum dithiocarbamate, zinc dialkyldithiophosphate, melamine cyanurate, molybdenum disulfide, and calcium salt of alkylaromatic sulfonic acid.