CAR WHEEL RIM

Steel wheels

Steelies are about as basic as wheels can get. Pressed from billets of steel using powerful hydraulic equipment, steel wheels have been standard on most low-cost vehicles for decades and dominated before alloy rims became cheaper to produce. Steel – an alloy of iron and carbon - is a harder metal than most other wheel materials, but this strength brings with it an increase in weight when compared to the likes of aluminium.

The basic way in which steel wheels are produced means that there is very little flexibility when it comes to design or any type of artistic flare. Different sections of a wheel are pressed out and then connected to form the entire wheel, ready to be used once the welds have been sufficiently ground down. This construction means that the only real way different designs can be implemented is to punch holes into the outside face of the wheel, be it for strategic airflow for brake cooling or for some much needed aesthetics.

Most companies will get around the unattractive nature of pressed steel wheels by slapping on a set of hubcaps with some badging to disguise the raw metal and imitate a set of more expensive and stylish alloys.

Alloys

Alloys until the last decade or so have always been reserved for the uppermost models within a manufacturer’s range, but they can now be specced in pretty much any city hatchback on the market if desired. Based on an aluminium or magnesium construction mixed with Nickel, alloy wheels provide a much lighter package when compared with a steel wheel of the same strength and can be cast in full by pouring molten allow into a pre-made mould.

Unsprung mass is a term you’ve probably come across before; it dictates the mass of components that are not supported by the suspension which includes the suspension components themselves, the brakes and the wheels. A lack of unsprung mass improves handling as it allows the suspension to interact in a controlled fashion with an undulating road surface and deal with the reaction forces from the road surface much more efficiently. This was one main reason why performance cars moved towards alloy wheels, with the lightweight construction helping acceleration and the overall dynamics of a car.

Multi-piece wheels

Most famously manufactured by BBS, wheels can be constructed from either two or three basic components. Two-piece wheels are made up of the wheel face (or centres) and the rim (or barrel), fastened together by rim screws that circulate around the circumference of the wheel centre. A ring of sealant is then applied to the join to further secure the sections together.

Three-piece wheels take it a step further, dividing the wheel rim in two to allow for a degree of adjustability in wheel width. All of this faff makes multi-piece wheels inherently heavier and slightly weaker than single-piece variants, but companies like BBS have developed a ‘rolled rim’ feature that brings the strength levels of its multi-piece wheels up to within reach of even single-piece forged wheels by tempering the once-weaker metal.

Forged wheels

Some of the strongest wheels on the market are formed by the art of forging aluminium. This is done by subjecting a billet of material to a ridiculous amount of heat and around 900 bar of pressure, crushing the metal into an extremely dense and immensely strong wheel. The enormous force of compression from the forging makes these wheels extremely light and many times stronger than an equivalent casted wheel.

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