Steel vs Cast vs Flow Formed Wheels
Steel vs Cast vs Flow Formed Wheels – Which is Better for the Budget Builder?
By Justin Banner
When it comes to wheels for the budget builder, a set of cheap, steel wheels are the first thing that comes to their minds. However, what you may want to consider going with a wheel that not only fits your budget but also gives you a benefit while using them. So, which is better for the price: steel, cast, or flow formed wheels?
If you haven’t checked it out yet, be sure to read our Wheel Basics article so you will have a better understanding about wheel design, sizing, and lug nuts. We will only just touch on those topics as they will be required, so if you need to know more about those specifics, check out that article. Once again, we’ll be calling it a “wheel” and not a “rim” except where applicable and you’ll see why in a moment.
Material and Construction Considerations
Let’s start with the general idea of each type of material a wheel can be made of. Well, at least at the budget friendly level. We could cover exotic materials like magnesium or carbon fiber, but that would be outside of the scope of a “budget friendly” (read: inexpensive) conversation. So, we’ll only cover steel, aluminum, and flow formed aluminum wheels.
Steel wheels are as simple as you can get as far as construction and material goes. You’ll find that they are two parts: the disc and the rim (also referred to as the “barrel”). The disc is the face of the steel wheel where you lug studs and hub center pass through and your lug nuts fasten to the drive flange. It can take on different, but simple designs but is usually a flat or has a very slightly concave face.
It’s usually made of an AISI 955X High-Strength, Low Alloy (HSLA) alloy steel. Its chemical composition is around 97.4-percent of iron with 1.35-percent of Maganese (Mn, not Magnesium or Mg), 0.90- percent silicon, 0.25-percent of carbon, 0.05-percent of sulfur, and 0.04-percent of phosphorus. It’s either cast or forged into shape before being welded to the rim.
The rim is usually made of AISI 1008 or AISI 1010 Hot Rolled, Low Carbon (HRLC) alloy steel. Once again, these two materials are virtually identical, so they have a chemical composition of 99.31- to 99.70-percent iron, 0.30- to 0.50-percent Manganese, 0.10-percent of carbon, 0.050-percent of Sulfur, and 0.040-percent of Phosphorous. There may also be minute traces of nickel, silicon, copper, and molybdenum.
Steel sheets are rolled into shape and welded into a cylinder. Its welding flash is trimmed off and the ends of the cylinder are cut true. The barrel is then formed into a rounded cylinder before the first forming and flaring is done for the wheel flanges. Each rolling forms the wheel center until you reach the final design and width that the disc is then welded to at the correct backspacing/offset.
Aluminum wheels, just like steel, are not a straight chemical composition, most notably the AISI 6061 (common in the US) or the AISI 6082 (more common worldwide). The differences in percentages is very small between them, but you’ll generally find both alloys contain around 96-percent Aluminum, 1.00-percent magnesium, 1.00-percent manganese, 1.00-percent Silicon, 0.35-percent chromium, and trace amounts of other chemicals. Again, those numbers are not exact and is the general average between 6061 and 6082. Once the aluminum alloy is smelted and sent off to the manufacturer, there are several ways it can be turned into a wheel. We’ll touch on two: casting and flow forming.
Casting and Flow Forming
Casting and flow forming share an initial start but diverge when it comes to the barrel forming. The aluminum comes in large pieces but is then melted down. From that point, the liquified aluminum is flowed into a casting mold.
For a straight cast wheel, the face and the barrel shapes are cast into that mold. There are many techniques to prevent the aluminum from creating stress spots as it cools, removing voids where aluminum doesn’t completely fill the mold, and other small tricks for improving the grain structure as the aluminum is flowed, but nothing else is done beyond that.
Flow Forming, though, goes a step further to improve the strength of the wheel’s barrel. Once the initial mold is done, the wheel is taken to a machine and spun while heated. A forming die is pressed against the wheel barrel at high-pressure and forges out the shape of the barrel. This forces the aluminum to take a tighter grain in a single direction.
This decreases the weight of the wheel (as compared to a cast wheel of similar width) and increases the strength of the barrel. This is important as you want a wheel’s barrel to be ridged and not hardened, which gives the wheel flex when struck by hard objects as you drive down the road or trail. You may bend a wheel, but you won’t crack or break it and that will prevent a dangerous deflation that can cause you to lose control of your Jeep.
Which Should You Use?
For the absolute in low-cost, you aren’t going to be the inexpensive price of a steel wheel. However, it will be heavy. While you may think that doesn’t matter in your trail Jeep, you also must consider the additional un-sprung, rotational weight you’re adding by going with a larger tire already. Adding even more weight with a heavy steel wheel will just create more work for your engine as you accelerate and your brakes as you decelerate.
The cast aluminum wheel will reduce the weight of your wheels and you’ll be able to get some amazing designs that you couldn’t get from a steel wheel. However, you also must be cautious that you get a wheel that is made of high-quality aluminum alloy and that the casting process is of equal or greater quality. Typically, if it has a name brand behind it, you’re generally in good shape but that doesn’t mean you shouldn’t do your due diligence.
Flow formed wheels are the top grade of cast aluminum wheels. You get the inexpensive entry of the cast aluminum wheel with the barrel weight and strength of a forged aluminum wheel. That also means they are going to be the most expensive of the three wheels we mention in this article. If you go this route, you aren’t going to beat what you’re paying for in terms of strength and weight until you go up to forged wheels.
WE ASKED WHICH ONE?
Ok, the honest answer is to go with the best you can afford. Yeah, it’s a cop out but it’s the smart advice to cop out on. If you need the greatest strength wheel at a middle-class income, you’re aiming for that flow formed wheel. If you’re lower-middle-class, you’re buying a cast wheel. If you’re on that ramen noodle diet, you’re going for steel. The most important part is to buy something with quality and not just the cheapest of the bunch.