Thereby, {TAIL ~ the step difference} of {HEAD ~ rigidity} is decreased while further raising the rigidity, the shearing stress is alleviated, and the bead part durability is enhanced 
Thereby , { TAIL ~ the step difference } of { HEAD ~ rigidity } is decreased while further raising the rigidity , the shearing stress is alleviated , and the bead part durability is enhanced
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH