a noise reducing chamber provided at an end portion of the noise reducing groove and having a predetermined depth that is greater than {TAIL ~ a depth} of {HEAD ~ the noise reducing groove} 
a noise reducing chamber provided at an end portion of the noise reducing groove and having a predetermined depth that is greater than { TAIL ~ a depth } of { HEAD ~ the noise reducing groove }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD