Nearly all ‘cheaper’ wheels will use a cast design, while more high-end wheels, such as Brixton Forged, strictly use a forged design. Unfortunately, many automotive enthusiasts don’t understand the difference between cast wheels and forged wheels, and end up purchasing something that doesn’t fit their needs. So what’s the difference between these two types of wheels?
What is a cast wheel? A cast wheel is made by pouring molten aluminum into a mold where it is formed to the correct shape, from there it is left to cool down. Once the wheel cools down, a trimming and drilling is performed. However, there’s one huge flaw with this method of production: porosity. Porosity is the physical space inside the material once it has cooled, and it allows for weak points to form. The cheapest workaround for this problem is to use larger tolerances, ultimately making the wheel heavier. This method of wheel manufacturing is quick and cheap, allowing for mass production.
Contrary to popular belief, cast wheels aren’t as terrible as they sound. A properly built cast wheel will weigh more than a forged wheel, but the build quality is typically sufficient for street use mixed with light track use. Heavy track usage is where you’ll notice the flaws of low-quality cast wheels (replica wheels), which can be dangerous. A high-quality cast wheel will survive heavy track use, but the heavier weight of a cast wheel is not ideal for motorsport activities.
What are forged wheels? There are two ways to make forged wheels: machine forging and mold-form forging. Nearly all forged wheels on the market use the machine forging technique. This process takes a chunk of billet aluminum and subjects it to high temperatures and tons of pressure which creates a compressed structure. This makes for a much stronger piece of billet. The large piece of forged aluminum is machine cut into the desired style and shape. This is the traditional process for building a forged wheel.
There are a few manufacturers, most notably Rays Engineering, who use the mold-form process of creating forged wheels. The mold-form process differs, in that the shape of the wheel is created during the forging process. By creating the shape of the wheel during the forging process, the grain of metal flows with the shape of the wheel. This makes the wheel much greater in strength. After they make the rough forging, a massive machine applies upwards of 10,000 tons of force to the inner and outer rim to create the design shape.
As stated above, cast wheels are inherently porous, whereas forged wheels are not due to the heat and pressure they undergo. That strength allows for less material to be used to achieve the desired structural integrity, resulting in a significantly lighter wheel. Oftentimes, forged wheels use a monoblock design, but they can also use a two-piece or three-piece design which allows for greater fitment flexibility.
Flow Form Wheels
If you’re a wheel geek like us, then you probably know that there’s a middle ground between cast and forged wheels: flow form or flow forged. This starts with a cast wheel that is purposely made narrower than desired. They then stick the wheel on a machine that spins the wheel while pressing the steel roller against the rim area, which compresses and stretches the barrel of the wheel. This results in forged-like barrel strength and weight. As you might have imagined, wheels built using this process fall between the cost of a cast and forged wheel.
Flow formed or flow forged wheels are a great middle ground for enthusiasts who want something stronger than a cast wheel without paying the premium for a forged wheel. Companies like Vorsteiner are very well known for their flow formed wheels. If you want something as strong as possible, then fully forged wheels are the way to go. However, for most enthusiasts, a flow forged wheel presents a nice balance between cost and strength.
What’s Best For You?
There is no right answer when it comes to deciding which wheel is best for you. It boils down to your intentions with the car, and how much you’re willing to spend on a set of wheels. In the end though, as long as you do your due diligence in researching the type of wheel and the manufacturer of that wheel, there is no wrong choice. If you’re using your car as a daily driver and nothing more, maybe cast wheels are a better option. On the other hand, if you mix daily use with light track use, flow form or flow forged isn’t a bad bet. If you plan on using your car for heavy track use, or you don’t have a strict budget, investing into a quality set of fully forged wheels is more than viable.
This is a very brief overview of this topic and there’s a ton left to talk about, such as load ratings and elongation. To summarize, remember that cast wheels are cheap but good enough for street use, forged wheels are expensive but will hold up to anything you throw at them, and flow formed or forged wheels are a nice middle ground between the two mentioned above.