Cast Wheels vs. Forged Wheels, What's the difference?
In summary, you will come across the following wheel descriptions:
- Cast wheels
- Flow formed wheels
- Forged wheels
- Monoblock 1-piece forged wheels
- 2-piece forged wheels
- 3-piece forged wheels
There are predominantly 5 different methods for construction of wheels. Each one varies in quality, weight, strength and price. There are "pros" and "cons" for each type.
The terms "forged" and "cast" are often used to describe a set of wheels to indicate the process used to manufacture the wheel. In the wheel industry forging and casting are the two leading types of processes used to manufacture wheels.
These are often the lowest priced wheels and are typically wheels which are found on production vehicles. Cast aluminium wheels are created by pouring molten aluminium into a mould that is shaped like a wheel. This allows for greater design flexibility and higher production volume compared to a forged wheel. In the past most wheels have been gravity cast (heavier and thicker). Today, low pressure casting techniques are used to substantially reduce porosity and mass.
Final machining work is performed to clean up the rough surface, followed by painting and surface finishing.
Pros: Low price, easiest to mass-produce, relatively quick production process, easy and cheap to replace a damaged wheel, quick delivery times as usually pre-produced
Cons: Limited shape and design options available, limited colours available (often only one or two finishes available - no custom colour choices possible), limited offsets and diameters available. Due to mass production, spoke details maybe not as sharp as a machined forged wheel. Often the heaviest of all wheel construction wheel types. A damaged cast wheel usually needs to be replaced rather than repaired.
Cast wheels companies include mainly German and also Italian companies which produce for the OEM market as well as aftermarket:
Flow-Formed wheels start out identical to cast poured wheels, but with different hoop thickness. The casting process above is used to create the spoke pattern only. Then the wheel castings are put into a flow-forming machine to form the outer hoops. This is done using high heat and high pressure rollers, which "flow-form" the outer hoop. This results in a stronger outer hoop, with aligned aluminium grain structure. The resulting wheel is a cast faced wheel with a hoop that has properties similar to a forged wheel. They are stronger and lighter than cast wheels.
Pros: Low Price, Lightweight, Higher strength than cast wheels, quick delivery times as usually pre-produced
Cons: Cast face still lacks the sharp edges and details of a machined forged wheel. Limited selection of sizes and diameters available. Often only 1 or 2 colours available, no colour choice option, hard to repair when severely bent or cracked, not every manufacturer is offering this type of wheels.
Manufacturer of Flow-formed wheels include:
The term "Monoblock" is used throughout the industry to describe the 1-piece forged wheels. "Mono" meaning one, and "Block" meaning it was created from one block of aluminium. The block in this case is actually a round bar stock of high quality, aerospace-quality 6061-T6 Aluminium Alloy. The round bar is pressed in a huge forging machine, to stamp out a wheel shaped blank. Forging is a hot working process, and helps to align the grain structure of the alloy. This results in a very strong, very lightweight wheel construction material. The wheel blank is then flow-formed to create the outer barrel shape. Following that process, the wheel blank is loaded into a CNC milling machine and there the spoke pattern is milled out.
Pros: Lightest of the forged wheel construction methods, build to order, perfect offsets possible for the wheel to sit flush with guards without using wheel spacers, various choices of colours, designs and finishes available, low unsprung mass*
Cons: Priced well above casted or flow-formed wheels, difficult to repair when bent or severely damaged, usually long production times between 4-8 weeks, depending on manufacturer
The unsprung mass of a vehicle primarily consists of the wheel/tyre/brake system and is essentially any mass not supported by the suspension of the vehicle. In order to maximise vehicle performance, the goal is to always minimise the unsprung mass. This means that wheels need to be as light as possible. By minimising the mass of a wheel, the handling and ride comfort are improved as it minimises the forces exerted on the vehicle chassis. This is accomplished by using for example high strength forged 6061‐T forgings as well as utilising high quality fabrication process. Selected designs paired with rigorous engineering aimed at minimising the mass while maximising the strength, stiffness and fatigue life, form the perfect wheel for maximum performance.
Manufacturer of monoblock forged wheels include:
2-piece forged wheels
These are often considered entry level forged wheels, as they are priced lower than 3-piece forged wheels. The centres start out as a blank of forged 6061-T6 Aluminium alloy, and the spoke patterns are CNC machined with a milling machine. The wheel barrel is also made out of forged aluminium material. On a 2-piece wheel, the centre is welded or bolted to the barrel of the wheel. It is the least common manufacturing process of forged wheels.
Pros: Low price forged wheels. Similar weight, appearance and quality as 3-piece forged wheels. Fully customisable in terms of colours and surface finish. Different designs and styles available. Wheels can be fabricated with custom offsets for perfect flush fitment with the guards.
Cons: Much more expensive wheels compared to cast or flow-formed wheels, bit more expensive to repair when outer lip is bent or severely damaged as the whole barrel would need to be replaced. Production times vary 4-8 weeks, depending on manufacturer. Least popular fabrication process, not many manufactures offer 2-piece forged wheels.
Manufacturer of 2-piece forged wheels include:
3-piece forged wheels
Three piece forged wheels are usually the most expensive wheel construction, mostly due to the assembly labour and components used. The wheels consist of three main pieces; the centre, the outer hoop (lip), and the inner barrel. These three parts are held together with a series of perimeter bolts. Silicone RTV is used to seal between the two hoops. Some manufacturers can also offer cast aluminium centres, to reduce cost. Three-piece variations give manufactures enormous flexibility in creating custom offsets and widths that sometimes are not available in a monoblock construction.
Pros: Truly perfect fitments available. Easiest of all wheels to repair if lip gets bent or damaged, as outer rings are easy to replace. Easy to paint or chrome plate lip. Endless options of colour and surface finish possible. Most popular forged wheels construction method, therefore a lot of options, designs and styles available.
Cons: Most expensive forged wheel construction, usually longest production times between 4-8 weeks, depending on manufacturer.
Manufacturer of 3-piece forged wheels include: