A wavelength detector is described. The tire is prepared by using a natural rubber instead of a synthetic rubber; an inorganic filler andor a biofiller instead of carbon black; vegetable oil instead of petroleum oil; and natural fiber instead of synthetic fiber so that the tire comprises a non-petroleum raw material in an amount of at least 75% by weight based on the total weight of the tire. It is possible to alleviate stress concentration generated on the bearing surface by forming a plurality of air channels capable of imparting directivity on an outer surface of the hemispherical bearing.