To prevent a serious failure such as the derailing of a wheel from occurring by realizing such a structure that can produce an easy-to-understand symptom on such a failure that may lead to the breakage of studs 20a and 20b.

The strength of one stud 20a of a plurality of studs 20a and 20b for fixing the wheel 1 forming the wheel to a hub 11b is reduced less than the strength of the remaining stud 20b. Also, the outer end opening of the wheel 1 is closed by a metal wheel cap 31. When a load exceeding the intention of a designer is applied to the wheel, the stud 20a is broken, and the tip half part of the stud 20a and a nut 21 threaded to that part are collided with a wheel cap 31 to generate noise. Since the remaining stud 20b remains without being broken, the wheel is not derailed.