Difference Between Cast, Flow Formed and Forged
Cast wheels are the most common type of manufactured wheel on the market. Casting is when molten aluminum is poured into a mold. After it cools and the wheel is formed, it’s drilled and trimmed to smooth the edges. This method is easier and less expensive than other methods, however there is a disadvantage. When the aluminum is melted into a liquid, it disrupts the geometric crystal structure of the metal. As it solidifies, the material’s structure can develop inconsistencies. This means that cast wheels can have failure points that crack under pressure. Manufacturers often use more material to try and prevent these issues which results in heavier wheels.
Flow formed wheels are the newest type of manufactured wheel on the market. They are also known as flow forged, hybrid forged or rotary forged wheels, however they are not actually forged. A cast wheel is heated to over 400 degrees and placed on a machine that spins. A spinning disk widens the barrel of the wheel, forming the desired width. Then it’s drilled and trimmed to smooth the edges. The simultaneous heat and pressure increase the strength of the barrel of the wheel. In terms of weight, durability and cost, flow formed wheels fall in between cast and forged wheels.
Forged wheels are stronger than cast and flow formed wheels, but for a price. This type of wheel is the most expensive to manufacture. In this process, a large, square piece of solid aluminum is heated to extreme temperatures and extreme pressure is used to compress it into the desired wheel shape. This causes grain refinement, which increases the strength and hardness of the aluminum. The inner crystal structure of the aluminum is made up of “grains” that shrink as the metal solidifies and compresses. This creates a tighter, denser and stronger structure. After the wheel is formed, it’s machined and drilled into the desired wheel type. Because forged wheels are manufactured this way, they use less material, resulting in lighter-weight wheels.
Monoblock vs Two Piece vs Three Piece
Monoblock wheels are the most common type of wheel and can be manufactured with casting, flow forming or forging. These types of wheels usually weigh less than multi-piece wheels. The disadvantage to monoblock wheels is that there are not many options for customization.
Two piece wheels have two separate components that create a single wheel. This type of wheel is made with a cast aluminum center welded to a forged aluminum barrel or a forged aluminum center welded to a forged aluminum barrel. This creates more options for customization such as, color combinations, different finishes, backspacing, custom widths and specifications for modified vehicles. Some disadvantages to two piece wheels are that they are a little heavier than monoblock wheels and they are higher in cost.
