The Real Difference
Quality. Safety. Performance. When it comes to choosing performance wheels to sell, as a buyer, you want a product to please the end consumer, as well as a product to represent your company in the best light possible.
So, what does the consumer want? And what will benefit your company most?
Based on our experience from the companies we’ve worked with, they prioritize quality and safety, shorter production lead times, and efficiency in application for the end consumer.
There’s just one problem: The world of wheels can be very confusing!
To help bring some clarity as you research which wheels to source, this article will cover the three main wheel options and how they relate to those goals in terms of strength, load bearing, cost, application, and production times.
The three-wheel types we’ll compare are:
- Cast Wheels
- Flow Form Wheels and
- Forged Wheels
Let’s start with the cast wheel. Casting alloy wheels is the most common manufacturing method on the market. Casting is a metalworking technique that’s been used in some form or another for thousands of years where hot liquid metal is poured into a mold and allowed to cool.
When it comes to manufacturing wheels, this is important for several reasons as it affects the performance, strength, and cost of the wheel.
To understand how the manufacturing makes a difference to the final product, let’s dive into how it’s made.
Wheel Casting Process
- First, aluminum alloy is poured into a mold by one of two methods: it’s either poured or drawn into the mold with a vacuum.
- The alloy then cools, and the wheel is formed.
- Time for the final touches: drilling, trimming, and more.
Now, what kind of wheel do we have? A wheel that’s strong enough for basic applications…
- A pretty look
- Infrequent laps around the racetrack
- Sports activities
- Custom dress-ups
- Anytime design counts more than strength,
- For a trip to the beach in a large SUV or a minicar
Essentially, they’re designed for lower load bearing applications.
The reason for this is that while cast wheels are more common, easier to manufacture, and therefore less expensive, they have an important failure point.
As the liquid alloy cools in the mold, there is a chance for greater porosity, or inconsistencies in the metal. There are different methods to lessen this, but the end result is a wheel with lower load bearing potential. These inconsistencies can also lead to cracking when under pressure. To counter this, more material needs to be used, which results in a heavier wheel than the other two manufacturing methods.
As cast wheels don’t typically have the strength or the lightness for serious performance, flow formed wheels, or forged wheels might be a better option for those applications.
Flow Formed Wheels
The second manufacturing process creates what is most commonly known as “flow formed” wheels. This is a relatively new method, that’s a sort of hybrid between forged and cast wheels (although it’s not to be confused with forged wheels as the process is entirely different.)
Flow formed wheels are a step up in load bearing capacity (and strength) and in a lighter weight from cast wheels.
Let’s take a look at why.
The Wheel “Flow Form” Process:
- Cast a thinner wheel than usual following the process above.
- “Flow Form” it. Here you take the unfinished cast wheel, and rapidly spin it on a machine while applying high heat and pressure to expand the width of the wheel.
The first main benefit here is a lighter wheel because less material is used. Different flow forming techniques and manufacturing processes result in a wheel that’s anywhere from 15% to 25% lighter than a cast wheel.
The second is increased strength. The flow forming process both compresses and stretches the metal, changing its composition and increasing its tensile strength. This leads to increased shock resistance and a higher load capacity.
Who Would Benefit Most From a Flow Formed Wheel?
Flow formed wheels are a great option for those who want something lighter and more durable than a cast wheel. On the track, for example, less weight leads to less rotating mass, a benefit for both greater acceleration and breaking efficiency.
Applications for flow formed wheels include;
- Everyday driving
- Casual racers in smaller cars
- Performance drivers who don’t require as heavy a load capacity.
Of course, you can expect a flow formed wheel to be more expensive than a cast wheel because of the technology and extended process used in its creation.
Finally, we have forged wheels. These are at the top of the wheel performance pyramid because they are the strongest and lightest wheels on the market.
Forged wheels certainly have a higher cost due to the custom manufacturing process. However, when quality, safety, and performance are at stake, if the wheels are subjected to sudden impact, a forged wheel resists cracks. And yet, when damaged, the wheel can be repaired if necessary.
It’s for these reasons that professionals in competitive racing as well as car enthusiasts who spend a lot of time on the track, want the best in performance, quality, and safety. For any situation where the wheels are under duress, forged is always the best choice.
Another reason many choose forged wheels is that they are fully customized to the client’s specifications. As such, depending on the manufacturer, the lead time to fulfill a custom order can vary. Working with a manufacturer who can complete the order within an acceptable time frame makes a huge difference for those who need a quality product.
So, what’s the real difference?
The difference between cast, flow formed, and fully forged wheels is all in the manufacturing process – and the effect it has on the end result. Weight for weight from one style to another, fully forged wheels are by far the strongest at the lightest weight. They have greater load capability and resist cracking, denting and breaking, making them the most durable and safe option on the market. For these reasons and the custom nature of forged wheels, this is the best option for those looking for the highest level of performance from their wheels.
Cast and flow formed can be great wheels depending on the applications needed and the clients’ ultimate goals in driving and performance. They each have potential inconsistencies in the metal because of the nature of casting, but if the wheels won’t be under frequent, heavy duress, it might not be necessary to choose forged wheels.
Rotary forged vs flow formed.
Flow forming is a fairly new technology, and each manufacturer does it slightly differently. However, any wheel that starts as a cast wheel, and is then manipulated is not a forged wheel. It will be in the middle between casting and forging in terms of strength, durability, and weight. So, when you hear names like “rotary forged”, it’s worth it to double check how the wheel is manufactured.
It’s likely a marketing term that a manufacturing company has given their flow-formed wheels to indicate the increased strength – even though they’re not forged at all.
Other names for flow formed wheels include “Flow Forged,” “Spun Forged,” and “Rotary Forged,” among others.
Are forged wheels worth it?
Forged wheels are certainly a step above the other wheels in terms of not only performance, quality, and safety, but also cost. That’s to be expected if you’re after the highest quality available. One question we hear often though is, “Are forged wheels worth it?”
The answer, of course, depends on the final application. If the wheel is for a car enthusiast who wants great quality but doesn’t actually get a lot of track time, they might be able to get away with flow formed or cast wheels. However, if you’ve got a true performance vehicle that gets a lot of track time, there’s really no question – forged would be the way to go.
How forged wheels are made.
A look at how they’re made explains why forged wheels are the go-to choice for racing professionals.
Here’s a simplified version:
- Starts with a solid chunk of metal. Unlike cast or flow formed wheels (which start with a cast wheel), where the liquid alloy is cooled in a mold, fully forged wheels start out with a solid piece of aluminum billet.
- Apply pressure. To form the metal into a wheel requires intense pressure to “hammer” the metal into a wheel. Two common methods include: mold forging and machine forging. Either way, essentially, the billet is exposed to high heat and then shaped via extreme pressure.
- Add the finishing touches. The wheel then needs to be trimmed, drilled or whatever else is required to achieve the final design.
The Wheel Forging Process
This process results in significantly stronger wheels than cast or free flow manufacturing because as the aluminum is pressed, the internal structure of the alloy changes, allowing the grain of the metal to adapt to the shape of the wheel. This process results in a structurally stronger wheel, with less material.
The benefits of forged wheels extend beyond strength, however. Due to the extreme pressure applied to the wheel, potential failure points typical to cast wheels, like porosity, cavities, and more, are eliminated. The compression of the metal also translates into increased wheel longevity, increased resistance against wear and tear, as well as increased performance and handling.
Why manufacturing method matters.
Choosing cast, flow form or forged wheels are all good choices. It really all comes down to what the car will be used for.
The manufacturing process chosen makes a difference in the structure of the metal itself; it determines how much load capacity, stiffness (or rigidity), and durability the wheel will have.
As mentioned above, the nature of forging requires extreme heat and intense pressure in order to form an aluminum billet into a wheel.
This changes the structure of the aluminum itself. The metal is now denser, with a grain that follows the shape of the wheel. This translates into:
- A lighter wheel (less alloy is required to form the shape and maintain strength),
- A stronger wheel (the density of the metal eliminates failure points due to porosity and the manufacturing process itself increases both the tensile and yield strength)
- A more durable wheel (again the density allows the wheel to hold up better against misuse and overloads, an indication of increased fatigue strength)
- Greater safety (A study by Alcoa shows that in general, forged wheels do not fail in impact tests, but that in similar tests, the cast wheels don’t always comply as well. whereas complying with the impact test requirements may be a tougher problem for cast wheel designers.)
- More freedom in design. (With increased strength at a lighter weight, designers have more flexibility to customize the appearance of the wheel, including its finish.)
As you can see, the manufacturing makes a big difference on the end result of the wheel.
Which choice is right for you? Again, it really depends on how you’ll use the car. For example, to quote Speed Academy, “To be clear, a properly designed and manufactured wheel is going to be perfectly safe on your road car regardless of whether it’s cast, flow formed, or forged. All other design parameters being equal, you simply gain the advantages of less weight and greater stiffness, and elongation should you decide to step up to a flow formed or forged wheel.”
On the other hand, if you’re a performance driver, you’ll need the benefits that a forged wheel offers, if nothing else, for safety reasons.
Why load rating matters
We’ve talked a lot about strength. Now let’s talk about load rating. The primary concern here is safety. Take a look at what a professional race driver has to say about the importance of the load rating…
“Whatever the case may be, as a racer I certainly want to know that the wheels going on my cars, especially if they’re going to see track time, have a serious safety factor built into their designed load rating as well as the best possible construction characteristics (like weight and elongation) my wallet can handle.”
Essentially, the load index of a wheel tells you how much weight it can carry. Also known as load rating, you can find the load index represented by a number found on the wheel’s sidewall.
The wheel load is determined by taking 50% of the heaviest axle rating of the vehicle (GAWR – gross axle weight rating). Example: if your heaviest axle weight rating is 3000 lbs. then your wheel load requirement would be 1500 lbs.
You’ll see the axel rating in the driver’s side door jamb, gas tank door, truck lid or in the glove compartment. You’ll have to look up exactly how the car’s weight is distributed and then place the wheels accordingly to ensure you have a safety margin in your wheel load.
One caveat to watch for is to remember that these are static load numbers. When racing or exposing the vehicle to technical off roading and the like, the extra strength you get from a forged wheel will give you a superior performance and safety margin to cast wheels, and in some cases, even free flow wheels.
How to Get The Wheels You Need
Are cast wheels, flow form wheels or forged wheels better?
To sum up, the answer lies entirely in what you need out of the wheels. The manufacturing process makes a significant difference in the safety, quality, and performance of the wheel. For example, if the application is for premium automotive, motorcycle, off-road, racing, and military wheels, forged manufacturing will likely be your best bet. This is because of the increased strength, performance and safety the forging process offers.
Whereas if you need applications for infrequent racing, or road driving, cast wheels, or even flow form wheels will be sufficient. However, remember that wheel load will also make a huge difference on performance and safety.
Which choice is best for your needs?