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  Wheels - Rims 2

Hardly anyone who is not professionally involved in the development of rims has more than a rudimentary insight into this topic. The idea that so-called alloy wheels are always significantly lighter than those made of steel is still widespread.

Already the comparison is difficult, because the rims used to be at least wider during a possible changeover and today often also increase in diameter. And because of this comparison, which is unfair for the new rim, it can happen that a wheel becomes heavier.

Especially since there is hardly any switch from steel to aluminum. Magnesium has long been in competition with aluminum. Both light metals can be cast as well as forged, the latter with increasing tendency. Even with a truck, a light-alloy wheel rim with a special design is considered chic these days (picture above).

So it's almost over with the forming of high-strength steels into rims and wheel discs, which are then welded together. The new material is even used for winter tires (picture below) and is now better protected, e.g. against road salt, thanks to a special coating. Only the lower price creates sales opportunities for these rims.

Steel wheels, no matter how artistically styled, have long been unable to keep up with light alloy wheels, some of which have very filigree spokes. When casting, the spokes can also be realized hollow. It is all the more astonishing how little material they use in relation to the wheel and tire mounts.

Even the shoulder of the rim can have a cavity.

There is no sharp distinction between aluminum and magnesium wheels. Usually, especially on forged wheels, it's an alloy with added silicon. The compaction of material otherwise attributed to forging can also be achieved partially, e.g. by pressure rollers with forces of several thousand tons.

The more filigree the design, the greater the effort and thus the price. And yet these wheels have to meet all the requirements placed on them. First of all, there is the unfortunately extremely popular drive upon curb stone edges, which may also be high. The rim may only warp to a very limited extent.

The aim is to avoid as far as possible the formation of cracks, which used to be rather frequent and which revealed clear defects in the internal structure, if they were noticed at all. It is amazing how little brittle both the cast and the forged material is nowadays. In poorer countries, severe deformations too are often straightened.

We do not even want to assume that there is a latent imbalance or vibrations in the high-frequency range that cannot really be corrected afterwards. Twisting of the tire on the rim, especially when starting off sharply, seems to be under control despite increasing engine power.

Of course, there are also the not always normal horizontal vertical movements of the vehicle when drifting or leaving contact with the ground. Sure, that rarely happens with the normal driver, but the rims have to be prepared for all these rigors, and the larger the wheel, the more difficult it gets.

The impulses are then also taken into account in these considerations, e.g. when driving through deeper transverse grooves in the roadway at undiminished speed. One hardly realizes the possible heat development on the rim that can emanate from a brake disc that has been driven to red heat.

In the past, such rims still had the privilege of being mounted on sports cars that were not too weighty. Today, they also very often adorn large SUVs, often oversized up to, say, 24 inches. Then you have to reckon with possibly proving your rigidity off-road, e.g. even with larger inclines, and then maybe at 200 km/h on the motorway?

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