Types of Wheels: Cast vs Forged Wheels
Aftermarket Wheels Explained
Early manufacturers of aftermarket mag wheels, like American Racing Wheels, began offering both magnesium and aluminum wheels from the same castings in the early 1960s. They’re called “aftermarket wheels” because they are not available from the car manufacturer. The wheels are obtained “after” the car is in the hands of the owner. Aftermarket wheels, often referred to as “mag wheels,” are the single biggest way to change the appearance of a vehicle. They can also improve handling performance, allowing for different offsets and widths to offer car owners a wider range of tire sizes. The same holds true for racing applications. They can even establish a nostalgic time period you are building your project car around.
Soon, Cragar Industries began making a hybrid mag wheel called the S/S wheel that featured five aluminum spokes cast with metal tabs, or what Cragar calls “clips,” in the back of the casting. These tabs were welded into steel shells or rims, then the entire assembly was chrome plated. This method reduced costs still further. Not long after, U.S. Wheel began making a five-hole or slot one-piece aluminum wheel called the Indy wheel that mimicked the Halibrand magnesium racing wheels (now made in aluminum and called Sprint Series wheels) used on both Indy roadsters and in drag racing.
But there are a lot of types of wheels for cars, as well as facts you need to know, before plunging into the almost limitless offerings available. So, what is a mag wheel? We can get you started with some aftermarket wheel basics to help you wind your way through the myriad of things you should know before making the wheel selection to personalize your hot rod, muscle car, or classic pickup. Then you can view the Speedway Motors wheels selection to outfit your ride.
Aftermarket Terminology: Rims vs Wheels
At times you’ll hear aftermarket wheels referred to as both “wheels” and “rims.” However, they’re really two different things. The difference between rims vs wheels is that the “wheel” is the center while the “rim” is outer band or shell. Calling a cast one-piece wheel or a multi-piece wheel assembly a “wheel” is more correct than calling it a “rim.” As in, “Those are some nice wheels you’re running on your car,” versus “Those are some nice rims you’re running on your car.”
Wheel Terminology and Accessories
There are a ton of terms applying to aftermarket wheels, as well as the little items that go along with wheels like different wheel studs and accessories, and even wheel fitment aids like Speedway’s WheelWise™ measurement tool, and let’s not forget how to measure wheel PCD so you are sure to get the proper wheel bolt pattern on your new wheels. With so many different wheel types, let’s start there.
What Are the Different Types of Wheels?
The major categories for wheels are based on how they’re made. They fall into three main types: cast, steel, or forged. Some are better than others, depending on their application. However, keep in mind that all aftermarket wheels must follow strict testing procedures outlined by the Society of Automotive Engineers, or SAE, in its SAE Wheel Fatigue Test Standards.
Steel wheels run the gamut from plain “steelies” like the Speedway Smoothie Wheel, a traditional custom car and hot rod wheel, to centers stamped with a simple decorative steel center. They’re generally the least expensive and are closely related to the basic steel wheels found on many stock cars and trucks. These are strong, durable wheels, but don’t offer the same custom look as cast or forged wheels. They’re also the heaviest type of wheels for cars.
Below, you can see the distinct types of wheels for cars, covering one-, two-, and three-piece aftermarket mag wheels. The two-piece wheels can either have a center welded, riveted, or bolted to the wheel rim. Three-piece wheels tend to be the riveted type and offer abundant variations of offsets and widths depending on which inner and outer shell is used. That’s because the width of each inner and outer shell determines wheel offset and backspacing; critical dimensions for determining the size of wheel you’ll need. You’ll find backspace and offset explained elsewhere in our Toolbox.
Types of Wheels: Cast vs Forged
When it comes to cast vs forged wheels, the strongest and lightest aluminum wheel is a forging. But because the process of making a forged wheel is more involved, it equates to higher costs. So, deciding on the appropriate wheels for your application factors how your vehicle is used, the look you want, but also what your budget will allow.
What is a Cast Wheel?
Cast wheels are mostly one-piece sand cast aluminum construction. Being one-piece cast or “monoblock” means there are lots of designs available, but sizes can be limited because each casting involves a new master or model. More than strong enough to withstand normal driving, they are not as strong as the other type of wheels for cars listed here. But they represent what we think of as the classic muscle car wheels.
The obvious advantage of cast over factory steel types of wheels is they feature unlimited complex and compelling designs with little excess material to remove after the casting process. That means less processes and labor involved in their production, along with aluminum being cheaper than steel. They are cheaper to make as well. Thus, you get the look of a racing wheel for less money. They’re heavier than a magnesium wheel, but easier to keep shined up, as magnesium corrodes quickly, requiring almost weekly maintenance to keep them looking polished. And they’re still lighter than a stock steel wheel.
What Is a Mag Wheel?
We’ve used the term “mag wheel” a lot so far, but mainly as a figure of speech relating to different types of wheels. In fact, the original “mag wheel” referred to aftermarket wheels made from magnesium. These wheels were available in cast and forged options, with many of the wheels from the 1930s through the 1960s being a cast variety for the aftermarket. Usually, forged magnesium was reserved for high-end racing wheels of the period. Magnesium wheels from this time, though highly sought after today, were known for being highly corrosive, causing owners to constantly wage a battle with the elements to keep the wheels clean, polished, and free of corrosion.
Additionally, these period mag wheels were known to be highly flammable. So much so that the typical fire hose would not put out a burning magnesium wheel, instead requiring a dry chemical extinguisher, or the smothering via dirt, sand, etc. For these two main reasons magnesium wheels were mainly replaced by cast and forged aluminum wheels in the aftermarket. Today, magnesium wheels are made with improved alloys that not only fight corrosion issues, but are not flammable either, though these are usually reserved still for high-end exotics and race cars.
What Are Forged Wheels?
When it comes to cast vs forged wheels, they often look the same. So, what are forged wheels? Being forged means the wheels are created under tremendous pressure via a forging machine, which aligns the grain structure of the aluminum for great impact resistance and anti-fatigue qualities versus a typical casting. It eliminates porosity, offering superior strength while giving the benefit of advanced looks, along with many varieties of offsets and widths. That’s because in most cases, they come as either two- or three-piece construction.
Forged wheels can also be made from a billet aluminum block forging. These are usually a two- or three-piece design with the wheel portion machined from a block or billet of aluminum. This is then welded or bolted into an aluminum rim. Rather than being press forged into a mold, billet wheels start with a solid cube or billet of aluminum that is then machined to create the wheel’s design. They’re a grade up from a strictly cast wheel in terms of strength. However, designs are limited to what pattern can be cut into them from a five-axis milling machine.
What Are Flow Forged Wheels?
There are two other aftermarket types of wheels we should mention. Flow forged wheels are like forged mags, but they are spun and compressed during the forging process. The difference between flow-formed and forged is that the forging process starts with heated billet aluminum that is formed under pressure. Flow-forged wheels are spun to compress the grain structure. They are both stronger than cast wheels and can be made thinner with more strength.
The other is carbon fiber wheels. These are used mostly in racing applications and can be considered the best racing wheels for a track day. They combine carbon fiber mat or strands with strong resins. Once the resin is introduced, they’re put under pressure like a forging. They are the lightest and strongest wheels you can buy, but they are meeting with mixed reviews when it comes to everyday use rubbing curbs and hitting potholes.
Best Muscle Car wheels
As we mentioned earlier, you can define an era for your muscle car based on the wheels you choose. And now you can also go with a stock-looking muscle car wheels in larger sizes that improves the look of your muscle car while also open to more available tire sizes. Generally, car companies in the 1960s and 1970s kept to a limited amount of 14- or 15-inch wheel sizes for their product lines. But the wider and taller wheels that look like those old 14- and 15-inch versions offer better looks, performance, and handling. So now you have the best of both worlds.
The best hot rod wheels are traditionally five-spoke wheels like American mags, and slotted dish wheels like the U.S. Wheel mag wheels. Both types of wheels give the classic mag wheel look reflecting that late-1960s through 1970s muscle car look because they are the same now as then. They’re the best muscle car wheels for cars of the era, hands down.
Best Street Car Wheels
In the 1950s, a few of these magnesium racing wheels found their way onto street cars, kicking off the mag wheel revolution. But, for the most part, these aren’t the best type of wheels for cars. Magnesium breaks down when exposed to moisture. And cast magnesium tends to be brittle and less forgiving than an identical wheel cast in aluminum. If you’re looking for some drag wheels to give your muscle car or hot rod a period look, you can have the appearance of magnesium with the safety and modern construction of aluminum. The same can be said for classic truck wheels.
Best Racing Rims
The best racing rims depend on the type of racing you’re doing. For drag racing, a forged wheel is the best option. For Sprint Car and Circle Track racing, beadlock oval track wheels are the way to go. A beadlock wheel has rings that tie the inner and outer tire beads to the rims. This keeps the tire better secured to the wheel and eliminates the tire rotating on the rim itself.
Drag racers in the late-1960s and 1970s would drill holes in the outer portion of the rim to screw the rim to the tire’s bead. This was an early form of beadlock. But today’s version adds a rugged but also cleaner look. They also add a certain extra dimension of wheel design based on how they are cut and by anodizing them in assorted colors or using different finishes making them a separate design element. Weld Wheels offers many beadlock style drag wheels. When it comes to constantly varying tire pressures from rock crawling to racing, it’s all about tire grip. To keep that tire secured to the wheel, beadlock wheels are the best racing rims.
Now that you have a better understanding of various wheel construction types, you’re ready to find that perfect set of wheels and tires for your ride to make it uniquely your own.
