What are Forged Wheels and Do You Need Them for Your Muscle Car?
There's a lot to think about when choosing a wheel for your muscle car. Style, of course, is crucial, but there's also diameter and width to consider, especially if you're looking to mount a larger-than-stock tire combo, or lowering your vehicle's suspension to the point where clearance might become an issue. Lower on the list of wheel criteria is how a set of rims is actually constructed.
Often times this characteristic is presented as a forgone conclusion: forged wheels are 'the best' and anyone who chooses anything else is only doing so to save cash. While it's true that forged wheels outperform more common cast wheels in a number of key areas, what is seldom discussed is whether any of this additional capability is meaningful on the street. Do you need a set of forged wheels for your muscle car? Unless you're hitting the track each and every weekend, you might be surprised by the answer.
Forged Versus Cast Wheel Construction
What is a forged wheel? The term refers to how the metal used to make the rim is worked. Specifically, the forging process starts with a single piece of billet metal, (typically aluminum, or another alloy) and then uses heat and pressure to form it into shape. The term comes from the traditional world of blacksmiths, who also worked metal using heat and pressure, although modern methods replace repeated hammering with a mechanical or hydraulic press that combines with a series of formed dies to create the wheel.
It's important to understand that the above process is extremely labor intensive. The presses required to compress a block of billet aluminum exert force that is measured in the thousands of tons, and they often take the form of multi-story machines. As a result, the cost of a forged wheel is often significantly higher than most other types of construction.
Why go through all of this effort and then push it onto the market with a hefty price tag attached? There are several benefits that make forging well worth the effort. Specifically, forged wheels are much lighter and stronger than same-size wheels that have been manufactured via casting, (where an alloy is melted into a liquid that is then drawn into a vacuum mold). By using a single piece of extruded aluminum billet, the grains in the metal are aligned, versus the random alignment found after being melted and then cast. This means less metal can be used in a forged wheel while still exceeding the strength found in a much heavier cast wheel. In general, a forged rim will be between 10 pounds and 20 pounds lighter than a similarly-sized cast rim, which gives you a total weight savings of 40-80 pounds per set.
That looks like very small amount of weight at first blush, but wheels represent unsprung weight, which is to say weight that isn't supported by the vehicle's suspension system (a category that also includes brakes and driveshafts). Motivating unsprung weight means overcoming its rotational mass, which requires as much as three times the energy needed to get sprung weight accelerating at the same speed. A similar multiplying effect is observed when braking unsprung weight, which means wheel weight savings translate more accurately into the 120 pound to 240 pound range when comparing unsprung weight to sprung weight.
Where Do Forged Wheels Matter Most?
Stronger and lighter are essential to anyone building a high performance muscle car, but it's important to understand that it's a question of degree. Saving as much as 240 pounds of weight in a track car is a major win, as it will improve handling, braking, and acceleration lap after lap. It can also make a major difference in a drag car's E/T.
On the street, however, that number represents a little bit more than the average weight of a passenger sitting beside you. Think back to how your muscle car drove with a buddy riding shotgun compared to when it's just you out on the road by yourself. Chances are the difference wasn't noticeable whatsoever, even with the accelerator pegged. In a powerful, relatively heavy muscle machine, adding and subtracting 120 to 240 pounds of weight is going to have a negligible difference on cornering, acceleration, and braking in day-to-day driving.
The phenomenal strength of forged wheels is also hard to take advantage of outside of a competitive setting. Bashing into curbing and repeated full-throttle launches can definitely beat up a rim to the point of breaking, as can banging into off-road obstacles again and again over the course of a weekend, but on the street these scenarios are few and far between for the average muscle car owner.
Save Your Cash
There are a number of alternatives to forged wheels that can come close to matching their unique capabilities. Some sophisticated cast wheel designs hover within a few pounds of a forged wheel, while flow formed wheels combine elements of both casting and forging without incurring the same level of expense.
It's hard to justify the additional cost of forged wheels outside of a race track, drag strip, or rocky off-road trail. For the vast majority of muscle car owners the benefits of paying more for forged won't be apparent in normal driving—or even at the occasional autocross or quarter mile appearance. It's really only with regular, repeated punishment that the durability and lower weight of forged wheels become worth the premium.
The best part about sticking with cast wheels on the street? It leaves a lot more cash in your pocket to spend on other mods that will make a more noticeable difference, including tires, brake upgrades, and suspension tweaks.
