The light-alloy wheel rim reduces, compared with customary steel wheel rim, the unsprung weight, it ventilates the brakes and helps to convey the heat more effectively. It is not by chance that wheel rims, together with headlights and rear lighting, play an important role in the sales of vehicle extras, particularly for younger people. They are an essential element of the individualisation of the mass produced motor car.
How it works
After the first world war, Bugatti introduced the light-alloy wheel into the motor vehicle area. Originally it was only used in motor racing, nowadays they can also be found more and more often in the mid-range and even in the lower price range motor cars.
Their design is still partly based on the former coach wheels or wire-spoke wheels. Being an aluminium-silicon casting with manganese or magnesium additives, particularly attractive forms can be produced. Although steel wheels, thanks to new developments, now also have even lower wall thicknesses and have become lighter, at the moment, they still only have a chance in vehicles where the emphasis lies exclusively on economic efficiency.In the above figure, a 3-part light-alloy wheel is shown. It is exactly, like the others, also a drop-base rim. The manufacturer has provided it with a sealing compound and it is bolted together. As far as the mounting of new tyres is concerned, there is no specific difference.
To optimise light-alloy wheels, e.g., the wheel bowl can consist of two or more cast parts and be joined by friction welding. This allows hollow spokes and even more weight reduction. Apart from the well known, as wheel rim material, magnesium alloys, recently synthetics are also appearing in their manufacture. While the materials used are progressing, the design is being based on former times. When are we going to have wire-spoke wheels made from light-alloys?
Another disadvantage of light-alloy wheels, is the high amount of care needed in winter. If thawed, salt-containing water is not removed, and the protective varnish shows damaged areas, irreparable corrosion develops. The corrosion characteristics of steel wheel rims have, at the same time, been improved, therefore, these are distinctly more suited for winter use. Anyone orders his new car with alloy wheels, should at the same time, order a set of winter tyres on steel wheel rims, even though a lot of people living in milder areas renounce the regular tyre changing in autumn and spring, or use all-wheather tyres. The alternative is a careful and frequent checking of the protective varnish. 09/09