All those elaborate wheel-arch forms we see on automobiles are the result of decades of evolution and the work of hundreds of designers looking at each other’s creative output. Are they done out of habit now?
Perhaps some designers have forgot the wheel arch is first a hole in the body for a wheel arranged so as to allow the wheel’s movement and manage water spray. Like many features on a car they are often drawn as sculptural entities or purely graphical forms. I personally have sketched shapes from purely a formal viewpoint: two blobs for lights, a block in the middle some lines underneath…. And there’s a car’s front end, divorced entirely from the relationship of each shape the thing it represents.
It is not a necessity that a wheel arch-cut out has to be as complicated, nuanced or constructed in the ways that we see on most cars. What might be the case is that designers are simply doing their version of a moulding around the wheel-cut outs on the bodyside. The decision to have a complex shape around the wheel cut-out is itself a choice. I don’t think that it is always the case that a designer approaches the wheel-cut out (or other shape) and thinks: what can or should I do here? Why is this thing here? The habit of creating yet another decorative surface around the wheel cut-out might be often just a default.
There are reasons why wheel-arches are very complex over and above the reason discussed above. Bonnets and window-lines are higher so that expanse of metal needs to be filled (does it?). And the silhouette of a car has been smoothed off so much that the only way forwards is back (the last C-class was more upright than the one it replaced – it’s smooth again). So that leaves graphics and sculpture to carry the task of distinguishing the car from every other car in the world.