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The Simple Guide To How Aftermarket Wheels Are Made

Over the last 10 years of selling aftermarket wheels we have come to the conclusion that it can be quite confusing for a normal person to figure out what wheels to buy. You have different wheels costing $300 or $3,000 with no real reason as to why. Why would anyone choose to buy a Volk TE37 vs. a Konig Ampliform? Or a Kansei KNP to a Stage Knight? While one of the major impacts of this is design, style and finish, another huge element of this comes down to wheel manufacturing.

Today’s article is meant to go over different types of aftermarket wheels from a manufacturing perspective and what to keep in mind as you begin searching for your next set of wheels at MartiniWorks. Let’s get into it, eh?

The Basics of Aftermarket Wheel Manufacturing

The great news is that all wheels sold on MartiniWorks have construction labeled. We think this is super important so you know exactly what you’re buying for your car. Should you have ANY questions, just hit us up using the chat bot in the corner and we’ll be sure to help out 🙂

Most aftermarket wheels are crafted from aluminum, favored for its balance of lightness and strength over traditional steel offerings. If you’re looking for steel wheels, we’d recommend upgrading your search immediately as it’s 2024 and we don’t need those anymore. Among the many manufacturing techniques, forged wheels stand out as the most strenuous and difficult to make. The result? A higher cost wheel.

In contrast, less expensive options like gravity cast wheels get you a wheel at a lower cost, but you typically get a heavier, less intricate wheel.

But there are manufacturing types that sit right in the middle of a fully forged set of wheels in comparison to a set of gravity cast wheels. These are the wheels that I would recommend most people buy.

Different Types of Aftermarket Wheels

The main manufacturing methods include low pressure cast wheels, rotary forged wheels, forged wheels, and multi-piece wheels – each with key differences in strength, weight, and design flexibility. Depending on your budget and plans with the wheel will decide what type of wheel you’ll probably want to snag.

Low Pressure Cast Wheels

Low pressure cast wheels are manufacturing process where molten aluminum is pumped into a wheel mold. While various forms of this exist, by injecting the aluminum vs. pouring like gravity cast wheels, low pressure cast wheels require less aluminum per volume and can create a more intricate design. Additionally, the casting process yields a higher density with fewer pores, resulting in a wheel that’s lighter and stronger than its gravity cast counterpart.

This density and strength do not dramatically increase the cost, making low pressure cast wheels a solid choice for most wheel manufacturers who are aiming to create a truly affordable wheel above anything else. You’ll find these wheels labeled in our wheels page with an icon!

Gramlights 57CR; an ultralight low gravity cast wheel.

Rotary Forged Wheels

This is our favorite type of wheel construction. Why? well because it blends the cast wheel process with characteristics of forging; giving you the best of both worlds. After the initial casting of the wheels’ face, the wheel is spun and heated, while pressure is applied to the rim to compress and strengthen the rim/barrel. The resulting wheel exhibits a toughness akin to fully forged wheels but is produced at a more affordable price point for folks like us.

To put this into math, a typical wheel barrel thickness in a lower pressure cast is 4.5mm. Take that and do the math on a 20×10 wheel and it’s quick to see why these have a tendency to get heavy. Comparing that to a rotary forged wheel, that same barrel thickness can be as minimal as 3.1-3.2mm. That’s a 30% reduction in barrel width without sacrificing strength as the grain structure within the aluminum barrel is aligned as the roller machines “forged” the barrel of the wheel.

Great examples of quality rotary forged wheels would be Stage Wheels, Enkei Wheels, and Konig Wheels.

These wheels are perfect for those who need a wheel capable of withstanding more than the norm, without the heightened expense of full forging. MartiniWorks’ lineup of rotary forged wheels promises to deliver heavyweight performance in a middleweight package.

Stage Monroe | An ultralight rotary forged wheel

Forged Wheels

The best are usually the most expensive and for good reason; these things can handle anything. Forged wheels are made through a solid billet of aluminum that’s transformed through intense heat and extreme pressure to create a lightweight yet incredibly strong wheel. The structural integrity of forged wheels means they can survive the rigors of high impact with less material, translating to near-perfect performance. Available in one-piece construction or as 2-piece or 3-piece, forged wheels can often be seen with the huge price tag and cult-like following in the automotive community. An iconic example would be the Volk TE37. With that said, typically forged wheels can also comin a multi-piece configuration. These are commonly referred to as “2p” or “2 piece” and “3p” or “3 piece” wheels.

Forged monoblock wheel | VR Forged D03R on MartiniWorks S2000

2-Piece Wheels

Two-piece wheels combine a center section – which can be cast, billet, or forged (typically forged) – with a separate rim barrel. They may be welded or bolted together, and while they are slightly heavier than their one-piece counterparts, they offer more design flexibility and easier repair options.

3 Piece Wheels

The big daddy of customizability in wheel design comes in the form of three-piece wheels. Comprising a central hub and two rim halves, often referred to as an inner barrel and outer lip, these wheels are custom-built, with the fit and finish being paramount. Assembled with exacting precision, 3-piece wheels from MartiniWorks are less common but provide exceptional adaptability for specific vehicle fitments, particularly in the realm of high-end sports cars. They also allow for part replacement convenience, adding a layer of practicality to their luxury appeal. Work wheels shines in the realm of multi-piece wheel configurations. Since we’ve worked with them for years, they are one of our top picks.

MartiniWorks is here to support your car building journey when it comes to aftermarket wheels / rims, providing not only a wide portfolio of wheel constructions but detailed knowledge to ensure our customers feel confident and excited about their purchase. Whether it’s the resilience of low pressure cast wheels, the balanced performance of rotary forged wheels, the best of it all in forged wheels, or the design flexibility of multi-piece wheels, we’ve got the perfect fit for your vehicle.

Work Zistance / 19×11 +6 & 19×12 +23 Rear

Forged VS. Rotary Forged Wheels

A common mistake is assuming rotary forged and forged wheels are the same. Typically, this is not the case. Rotary forging focuses on the barrel of the wheel, whereas the face is constructed using a low-pressure cast process. A forged wheel is constructed exclusively from a dense billet aluminum and cut to form the face design prior to heating and stretching the barrel to the width specifications. See our super cool table below:

Feature

Forged Wheels

Rotary Forged Wheels

Material

Dense billet aluminum

Molten aluminum, hardened by rotary process

Strength

Superior

Enhanced, close to forged

Design

Artistic flexibility

Can be detailed, but not as intricate as forged.

Price Point

High

Medium to low

Comparing Casting Methods of Low Pressure Cast Vs. High Pressure Cast

If you want to know how different types of casting methods that exist, then this is for you. Note that most aftermarket wheels are made in low pressure casting model. Gravity casting, the simplest and oldest casting method, relies on clearly defined laws of physics, where molten aluminum is poured into a mold and left to solidify, pulled by gravity. This process typically yields heavier wheels, as the lack of density necessitates increased material volume to maintain strength.

Advancing a tier, low-pressure casting employs a slightly more complex technique, pushing molten aluminum into the mold under – you guessed it – low pressure. This actively reduces the formation of microscopic bubbles inside the structure, resulting in a wheel that’s lighter yet stronger than its gravity cast counterpart. Low-pressure cast wheels strike a balance between quality and cost-effectiveness, offering enhanced properties without breaking the bank.

At the top of the casting hierarchy, we encounter high-pressure casting methods, notably Low-Pressure Die Casting (LPDC). LPDC trumps earlier methods by delivering a denser and stronger product, achieving a fine balance between weight savings and strength. However, this method commands a higher cost due to its more sophisticated production requirements.

Each casting method stamps its unique mark on a wheel’s density, weight, and strength. As the complexity and pressure of the casting process increase, so too does the cost, but the benefits of improved performance and lightweight characteristics can be invaluable to the discerning customer.

Casting Method

Process Details

Wheel Density

Wheel Weight

Strength

Gravity Casting

Molten metal filled by gravity

Normal

Heavier

Standard

Low-Pressure Casting

Molten metal injected under low pressure

Higher

Lighter

Enhanced

High-pressure Casting

Molten metal injected under high pressure

Highest

Lightest

Superior

Strength Vs. Weight of Aftermarket Wheels

It’s a common misconception that the lighter the wheel, the better it is. That’s not true. Weight savings on wheels is a great start to saving unsprung weight, but shaving every ounce you can will result in a wheel that can’t handle impact. The story of wheels shattering vs. bending is the difference between wheels being made poorly and/or with too much weight savings, or bent and able to safely pull off to the side of the road. See fancy table #2:

Material Type

Strength

Weight

Manufacturing Process

Steel

High

Heaviest

Traditional Stamping

Aluminum (Gravity Cast)

Standard

Reduced Weight

Gravity Casting

Aluminum (Low-Pressure Cast)

Enhanced

Lighter

Low-Pressure Casting

Aluminum (High-Pressure Cast)

Superior

Lightest

High-Pressure Casting

Aluminum (Forged)

Maximum

Optimal Lightness

Forging Process

So what’s the point of knowing about wheel construction?

With our introduction of defining whether a wheel is a replica design, inspired by design, or original wheel design, we’ve found that everyone thinks that replica design = bad. Again, that’s just not true. The same way that if it’s an original design = good. Instead, we want you to think that the entire wheel matters; not just how it looks. Aluminum wheels made of low pressure casting, rotary forged, and fully forged all help determine the price of a wheel and also tells you whether a wheel was made….well. One-piece wheels can be featured in all version of manufacturing, but as you jump into multi-piece wheels, the price (& the quality) typically goes up.

So if you’re on a budget, a low pressure cast wheel will do. The cast center may add a bit of weight, and the design may not be as super aggressive as something more expensive, but that doesn’t mean it’s bad. For this, we recommend Aodhan wheels.

If you’re looking for something with a bit more strength, something that can be dirt dropped and tossed around, then we recommend looking for that rotary forging label. The aluminum alloy is put through a forging process on the barrel of the wheel saving weight and giving you a stronger wheel. Bonus points, you’ll see greater color variety in these wheels too (along with chrome-plated wheels which is rad). For this, we recommend Stage Wheels.

And finally, if you’re looking for a no-expense spared style wheel that can be built to withstand just about anything and doesn’t sacrifice a single element of what makes a wheel a wheel, then we recommend a forged wheel. Ultralight, strong as hell, can be made in a million sizes, and you can tell all your friends you have a forged wheel. For this, we recommend Volk Racing.

But what questions do you have? Let us know through our little chat bubble and we’d be happy to help out. Sorry for being big wheel nerds. We just love this stuff!

Alex Martinez

My name is Alex, or Alex Martini (Alex.Martini__) and I love building unreliable cars. From track, road, drag and drift, there really isn't a motorsport I love. PS if you're reading this, just know that we've got some WILD builds coming for MartiniWorks that we're really excited to share with you :)