When talking about alloy wheels you will often hear the words ‘alloys’, ‘wheels’ and ‘rims’ used fairly interchangeably. In fact, these are similar, but there are important distinctions between them. The most obvious is the wheel/rim distinction, where ‘wheel’ refers to the entire cylindrical component and the rim refers to the outer edge of the wheel that holds the tyre. ‘Alloy’ of course means the mixture of metals, typically aluminium or magnesium, from which the wheel is made.
Whilst the most common alloys are magnesium and aluminium, there are differences between the two that have lead to one becoming much more common in modern wheels. Magnesium alloys offer superior performance and are thus sometimes used on racing cars, however they have fallen out of usage on new road vehicles, being mostly confined to class cars. This is due to improvements in the aluminium forging process and inherent flaws in the use of magnesium, such as its susceptibility to pitting and corrosion, as well as it being difficult to extinguish if it catches fire.