Forging is a non-cutting forming process for material in a heated, solid condition. In order to generate the highest degree of material density and weight reduction at top performance from our high-strength and durable aluminum or magnesium alloys, they are further enhanced in a complex forging process. This entails placing the heated star hub or the entire wheel blank in a press and compressing it in several work steps at 5000 to 8000 tons of closing pressure to further densify the material in a special form known as a matrix. In between the individual work steps, the blank is repeatedly heated to approx. 400 degrees centigrade. As a result an optimal material structure is achieved particularly at the areas of high strain, the wheel can be dimensioned smaller, and is thereby lighter in weight.
(source: www.bbs.com)
If light alloy wheels consist of more than one component, the term multi-piece light alloy wheels applies. Two-piece BBS light alloy wheels consist of rim and star hub; three-piece light alloy wheels of two rim halves and the star hub. The individual components are securely connected with titanium bolts.
(source: www.bbs.com)