What is the difference between cast and forged wheels?

Cast wheels use a mold, or "negative", into which molten alloy metal is poured, and the result is then machined to form the final shape of the wheel. They have the advantage of requiring significantly less time and effort to manufacture than forged wheels (and are therefore more cost effective), while maintaining a relatively light weight and adequate strength. Forged wheels use incredible amounts of pressure, combined with lots of heat, essentially smashing the alloy to form the shape of the wheel and keeping a much more uniform molecular structure. The advantage of this manufacturing process is that the wheel can use significantly less material (sometimes up to 30% less than a cast wheel) to achieve a lightweight wheel but very strong wheel.