Alloy wheels are specific wheels have been made out of aluminium or magnesium, with certain other elements added. They can come in various shapes and sizes and even the finish can differ greatly between models or brands.
Why use alloy wheels
Alloy wheels are lighter then steel wheels, which makes it easier for suspension to follow the shape of the road. When a wheel is very heavy, it holds more momentum when moving. This require more energy from the suspension to push the wheel down after the wheel has been lifted up. This occurs when a wheel follows a bump at high speed. The bump in the road throws up the wheel, requiring the suspension to push the wheel down and hold it on the road. Alloy wheels are lighter and require less energy to be pushed back down again, increasing road contact and overal control of the vehicle.
Another advantage of the alloy wheels is the casting process that allows for different sizes and shapes. This makes it possible to put more creativity in the design of the wheel, making the wheel a cosmetics attribute of the vehicle. Aftermarket wheels have become big business in the last 75 years.
Because good quality alloy wheels are non-ferrous, they do not rust and therefore do not require any paint. Bare metal wheels can even be polished to chreate a chrome-like finish. These type of finishes can also be referred to as “bare alloys”.
Cleaning alloy wheels
Cleaning alloy wheels can differ greatly between types of finishes. When alloy wheels are painted, these can be treated like any other surface. Due to cost, some types of painted alloys are painted via powdercoating, while others are spraypainted. Although powdercoating leaves a stronger and harder finish, it suffers from more orange peel and is less easy to correct. Spraypainted wheels can have a finish that is as good as that of regular paintwork and are often used for cosmetic reasons.
Unpainted alloy wheels may require more special care, because the surface is the metal itself, with no clear protectant. Although aluminium creates its own protection when coming into contact with air (forming a small layer of aluminiumoxide), magnesium reacts to air by creating a similar layer, but this layer is not completely clear, tarnishing the polished look. This magnesiumoxide layer is very difficult to remove and impossible to prevent. This means that magnesium wheels will more often require polishing to keep the shine to a maximum level of gloss, whereas aluminium wheels will remain glossy for longer. Both metals can react to certain type of chemicals. The level of pH is irrelevant, even though this is common blame for spots in the finish. The type of chemical, or the chemical reaction caused by contact with non-ferrous metal is often the problem that causes corrosion at the surface. If not treated quickly, this can leave permanent damage.
A proper form of protectant, for example: a ceramic coating, can prevent damage from these chemicals in many cases. Although strong chemical are also capable of damaging the ceramic coating, requiring it to be re-applied.
The biggest issue lies in corrosive products used in chemical cleaners. Although often used in the same sentence as “caustic”, these are different properties. Corrosive chemical “eat” away at the surface, whereas “caustic” refers to alakalis (pH greater dan 7).
Polishing alloy wheels
Depending on the finish of an alloy wheel, the polishing process differs. Painted alloy wheels can be polished regular polish that would also be suitable for bodywork and regular painted surfaces. In the case of powdercoated finishes, it may require a stronger polish with more cut to get the desired effect. Due to the irregular shape, a special attachment can be helpful. Polishing cones can be used, just like polishing balls. But there are also extra small backingplates available that can be mounted on a or rotary to polish very small surfaces.
Unpainted alloys are better off being polished with a metal polish. Although a generic metal polish can help, some manufacturers decided to create special formulas based on the type of alloy used. This means you can get polishes specifically aimed at magnesium alloys of aluminium alloys. Getting a flawless finish on metal might require extensive polishing as the amount of surface you remove while cutting is less then that of paint. These metal polishes can also be used with the attachments described above, such as the polishing cone of polishing ball. Although some manufacturers make special metal polishing pads, a normal polishing pad should be good enough to achieve a very good finish.
Technically incorrect term
Although the term “Alloy Wheels” is generally aimed at wheels that are different then standard steel wheels, this would be technically incorrect. Steel wheels are made from a combination of iron and carbon, making it an “alloy”. However, if referred to alloy wheels, most people are referring to wheels that have been made from an alloy from aluminium or magnesium, which commonly has a different shape and/or finish then steel wheels. In some other languages the term “light metal” is used, which refers to the difference in weight compared to steel wheels, and does not refer in any way to the type of material used. A good example is the Dutch “licht metalen velgen”, which means “light metal wheels”.
In the American language, these wheels can also be referred to as “mags”, which is short for magnesium. This is due to the first alloy wheels being made from magnesium. It wasn’t until the aluminium casting refinements allowed for better quality casting, that the magnesium wheel was the more popular type of alloy wheel.
Difference in quality
Although the difference can be small between certain models or brands, the difference on real life can be very dangerous. A quality alloy wheels should be capable to absorb certain impacts. Meaning the metal has to be have a certain amount of ductility. In layman terms, the material should be able to deform slightly without cracking or breaking on impact. Alloy wheels that have been made poorly can not withstand the impact and will shatter, making it impossible to control the vehicle. Cheaply made alloy wheels might look the same, and weigh almost the same as a quality alloy wheel, but will turn a dangerous situation into a deadly situation. Driving over a larger pothole at average speed can shatter a poorly made alloy wheel. Unfortunately, there are very few laws regarding the specifications for after market alloys. Germany is one of only a few countries that demand that aftermarket mods (including alloy wheels) are reported to the insurance company. These wheels need to have a TÜV certificate, which check if the wheels are of good quality.