The Lowdown On Wheel Tech
Wheels are probably one of the least understood and yet most important part of your 4x4's drive system. Most of the time, people choose their wheels simply by what design looks good to them. While this is an important aspect, wheels perform a critical function. Select the wrong one for your application and you could create a vehicle that's miserable to drive, or worse yet, cause an accident. From the basics of choosing the right size for your tires to the critical elements of load ratings and construction type, there are plenty of opportunities to get it wrong. That's why we'll spend the next few pages sharing tips with you that will help you find the wheels that are right for the function of your vehicle.
Material and Construction
For the most part, wheels are made from steel or aluminum. Steel was once favored for its low cost and high strength. For four-wheeling, it offers one huge advantage: When you smack a rock, the wheel bends instead of breaking. Of course, the wheel will need to be replaced or fixed eventually, but it keeps you going. If you live in a salty climate, steel wheels will need to be sandblasted and painted every few years. For the 4x4 market, there are several steel wheels available. Generally speaking, they are the least expensive option.
Aluminum was first used in wheels because of its light weight. The wheel and tire combination rotates mass, and it is unsprung weight (it's on the ground side of the suspension system). A reduction in unsprung weight results in better fuel economy, better acceleration, and better braking performance. The weight of the tire has a much greater affect on this because it's further from the axle centerline, but saving five pounds per wheel still makes a difference. In the early days, aluminum wheels were expensive and manufacturers hadn't figured out proper finishes, so the wheels became corroded and pitted over time.
Things are quite a bit different today, driven partially by the fact that nearly all original equipment wheels are made from aluminum. Aluminum wheels can be very affordable now, and there is quite a variety of finishes that offer long-lasting, low-maintenance appearance, and look good, too.
You may hear people talk about how much better forged aluminum wheels are compared to cast. While it is true that forged wheels are stronger and they weigh less, nearly all the wheels you'll find in the 4x4 market are cast. Forged is much, much more expensive, and cast aluminum wheels have improved significantly in strength and quality over the past 20 years. Forged wheels are mostly used in racing and in applications that require extremely high load ratings, such as tractor trailers.
Most of the aluminum wheels offered in the off-road market are made from A356 alloy, and they are made using a low-pressure casting. This process uses low pressure to draw molten aluminum into the casting form instead of relying on gravity. The result is a higher-density wheel with less porosity, which is good for consistent strength and minimized chances of structural wheel failure.
While it's usually pretty easy for a person to decide whether they want a chrome look or high-gloss black, it is easy to overlook the function of the wheel finish. In addition to how the wheel looks when it's new, the finish dictates how much work you'll have to do to do keep it looking nice. While chrome and paint are your choices for steel wheels, here are the more common finishes for aluminum, with the pros and cons.
Chrome: One of the easiest finishes to maintain, chromed aluminum gives you the advantage of an aluminum wheel with a bright shine that is easy to clean and maintain. This finish is mirror-like, and it resists corrosion and pitting. Lower-quality chrome can crack and chip over years of exposure to rough elements.
Polished: This is another bright finish, but isn't quite mirror-like. It's often considered a more refined look. Drawbacks are that it requires regular cleaning and polishing to maintain a bright finish, but the advantage is that it can always be brought back to the original finish.
Powdercoat: This provides a range of color options with a highly durable finish. It is very easy to maintain and it resists scratches, corrosion, and pitting. Popular colors today are black, silver, and shades of gray. However, powdercoat can come in virtually any color, and in some cases it may be more affordable than paint.
Clearcoat: A finish that got a bad rap in the '80s (some OE wheels had their clearcoat crack and peel after a few years), a clearcoat is a protective coat over a color or the natural aluminum material. A high-quality clearcoat is easy to clean and resists corrosion and pitting. Paint with clearcoat is one of the most common finishes on modern aluminum wheels.
Make Sure It Fits
Ironically, this is one of the most overlooked factors in choosing a wheel, and it is one of the most important. We can't tell you how many 4x4s we see with the absolutely wrong wheel size or backspacing, and it's because the owner didn't know what questions to ask. A lot of local tire stores are very good at helping you choose the right wheel, but there are also quite a few who try to stock as few parts numbers as possible and make whatever they have fit your vehicle.
There are really only three things you need to know to nail wheel fitment. The first is the simplest: The diameter of the wheel needs to match your tire! If you have a 305/65R17, you'll need a 17-inch wheel.
The next is more difficult: The width of the wheel needs to be appropriate for the width of the tire. Every tire manufacturer gives a specific range of recommended wheel width for the specific make and size tires. Find the chart online and use it. Generally speaking, tire manufacturers recommend a wheel that is two to three inches narrower than the tire's section width. We usually prefer to stay on the narrow side (but still within the manufacturer's range) because the extra bulge of the tire sidewall on a narrow wheel helps protect the wheel lip against debris. But going too narrow compromises the tire's ability to provide road traction and can decrease how well the tire seats on the bead of the wheel. A wheel that is too wide for the wheel also compromises the tire's performance and the bead seal.
By far, the most difficult part of tire fitment is backspacing or offset, depending on which wheel company you're talking to. And these two ways of measuring the same thing are not the same.