Boot for constant velocity universal joint

A boot for a constant velocity universal joint, the boot comprising:

• a large-diameter-side mounting portion, which is to be mounted on an outer peripheral surface of an outer joint member of the constant velocity universal joint, and is to be fixed to the outer peripheral surface of the outer joint member through fastening with use of a boot clamp;
• a small-diameter-side mounting portion, which is to be mounted on an outer peripheral surface of a shaft, and is to be fixed to the outer peripheral surface of the shaft through fastening with use of a boot clamp;
• a bellows portion configured to integrally couple the large-diameter-side mounting portion and the small-diameter-side mounting portion to each other;
• and
• a cylindrical shoulder portion, which is formed at a bellows portion-side end of the large-diameter-side mounting portion, and is connected to the bellows portion through only two auxiliary crest portions and only one auxiliary trough portion between the only two auxiliary crest portions,
• wherein one of the only two auxiliary crest portions on a bellows side is connected to an axial end of a bellows of the bellows portion axially closest to the large-diameter-side mounting portion, and another of the two auxiliary crest portions is connected to the cylindrical shoulder portion,
• wherein a radial distance (H1) between a thickness center of each of the auxiliary crest portions and a thickness center of the auxiliary trough portion is set shorter than a radial distance (H2) between a crest portion and a trough portion of the bellows portion other than a crest portion and a trough portion of the bellows portion closest to the small-diameter-side mounting portion,
• wherein a diameter (D1) passing through a center (Ho) of the radial distance (H1) between the thickness center of each of the auxiliary crest portions and the thickness center of the auxiliary trough portion is set larger than a diameter (D3) of the cylindrical shoulder portion, and
• wherein the boot has such a deformation mode that, when the constant velocity universal joint forms a high operating angle, the auxiliary crest portions overlap each other in a radial direction of the boot on the outer peripheral surface of the outer joint member such that the boot is configured to handle an operating angle equal to or greater than 50 degrees.