Cast or forged: the analogy that makes it all clear

• Module: Forged or cast
• Level: Beginner
• Reading time: 4 min

If you are interested in wheels, two words keep coming up: “cast” and “forged”. You will be told that forged is better, more expensive, more noble. But why? What is the real difference? Forget the technical jargon. A simple kitchen analogy will make everything clear.

Picture two ways of making a metal object

To make a wheel, you start from aluminium. But it can be worked in two very different ways.

The cast wheel: liquid metal poured into a mould

For a cast wheel, the aluminium is melted until it turns liquid, then poured into a wheel-shaped mould. It is left to cool, the metal hardens, and the wheel is taken out of the mould.

It is exactly like pouring cake batter into a tin: simple, quick, inexpensive.

The problem? As it cools, the liquid metal leaves tiny pores and invisible gaps inside. The structure is adequate, but not perfect. A bit like a cake with small air holes inside.

The forged wheel: metal compressed under extreme pressure

For a forged wheel, the metal is not melted. You take a solid block of aluminium and compress it under colossal pressure, several thousand tonnes, to give it its shape.

Now imagine that, instead of pouring a batter, you take a dough that is already dense and press it with all your strength to drive out the slightest air hole. The result is a material without voids, without weak spots.

That is forging: the metal is not poured, it is compressed. Its internal fibres line up.

The result of this difference

This simple difference in manufacturing changes everything:

A cast wheel is heavier and more fragile, because its structure contains these micro-imperfections. A forged wheel is lighter.

To the naked eye, two wheels can look identical. But inside, they are two different worlds. One is poured, the other is forged from the solid material.

You have grasped the essentials

Just remember the image: cast is liquid metal poured into a mould. Forged is solid metal compressed under extreme pressure.

This distinction is the basis of everything. In the next lesson, we will see in concrete terms why this difference makes a forged wheel almost unbreakable, where a cast one can crack.

The Onyx approach — At Onyx Forged, we only work with forged wheels. Each wheel starts from a block of 6061-T6 aluminium compressed under very high pressure. This choice is not a commercial one, it is a technical one: it is the only method that guarantees the lightness and strength worthy of an exceptional car.

This lesson is part of the Onyx Academy, the free course on custom forged wheels.