Bicycle wheel some other fixed point may be used as a reference mark, however this is less accurate. At one end of each spoke is a specialized nut, called a nipple, which is used to connect the spoke to the rim and adjust the tension in the spoke. The nipple is usually located at the rim end of the spoke but on some wheels is at the hub end to move its weight closer to the axis of the wheel, reducing the moment of inertia. Until recently there were only two types of nipples: brass and aluminum (often referred to as "alloy").
Rim (wheel) millennium BC, an iron rim was introduced around the wooden wheels of chariots to improve longevity on rough surfaces. A standard automotive steel wheel rim is made from rectangular sheet metal. The metal plate is bent to produce a cylindrical sleeve, and then the two free edges of the sleeve are welded together. At least one cylindrical flow spinning operation is carried out to obtain the desired thickness profile of the sleeve—and the desired angle of inclination relative to the axial direction in the zone for the outer seat. The sleeve is then shaped to obtain the rims on each