If memory serves, Piet Mondrian had a huge row with Paul Klee or Wassily Kandinsky about whether diagonal lines should be allowed in art. Has there been such an argument in car design?
It’s to do with bumper to body shutlines which leads to what might be the only semi-scholarly study of the evolution of the rear car bumper on the whole of continental Europe.
This has been at the back of my mind for ages before finally leading me to go on a binge of iPhone photography. That means the images are hasty, murky and not nicely composed. The thing to look out for is the evolution of the rear bumper from a separate item to a fully integrated item. It’s the intervening stage that captures my interest. During the middle period the designers aimed to have the body-to-bumper join horizontal as it had been ever since bumpers were a bar of chromed steel wrapped around the ends of the car.
Some points emerged from my study.
- On a large car there is more scope to keep the bumper to body panel gap horizontal which means it is more harmonious with the flow of the surface.
- The more of the car that is plastic the lighter it is. This explains the tendency to push that bumper-to-body line as far forward as possible.
- With this in mind, a huge bumper and a diagonal line cutting across the body implies cheapness.
- If you want to design an expensive-looking large car, having a big bumper with an ugly diagonal line (see above, see also Insignia “A”) is not the way to go about it.
The Citroen C6 is another early example of the unwelcome huge bumper to body cutline. Irregularity across the gap ruined the flow of the highlights.
It is clear that production engineers have made huge strides in getting tighter and tighter panel gaps. However, on pale coloured cars the black line of the gap is still all too evident. On a small car a 10 cm line is not a very big deal. On C-D class cars such cuts are quite unsightly. I’d suggest that the impression of quality is not aided if there is a 60 cm diagonal line cutting across the front-to-back flow of the surface.
And this is the job done well. The S90 (above) gets it right. What we learn to notice in today’s sermon is that the diagonal cut says cost-cut.
(Note: the 2000 Opel Corsa C has a second piece of plastic around the wheel arch. It’s silver coloured in the photo above. And the Meriva’s arch and rear bumper is inspired by the Audi A2.)
Driven To Write 
Richard, an interesting analysis. Decades ago, my Dad told me that the sign of a quality car was an unbroken line from bonnet along the bottom of the side windows and onwards to the back of the car. This has stayed with me. I will now add bumper shut lines.
I had thought the current Panamera (which, if nothing else, does look expensive) had a diagonal line, but actually the shut line is rather more sophisticated.
Incidentally, are people very fond of towing things in Denmark?
You can be sure Porsche have been really, really strict with the plastic moulding and fit of the rear bumper. The Opel, Ford and PSA cases are all deficient in this regard. The Porsche looks tidily done.
Denmark: towing is popular, yes. Watch out when walking between parked cars. Not everyone has a tow bar cap fitted.
I will respond to this in more detail when I have time, but a quick observation – all the most egregious examples tend to have the plane of the cut inclined more towards the vertical than the horizontal. Something to do with our eye/brain correlation, perhaps – a car is longer than it is tall, so a horizontal cut works with our ingrained visual expectations rather than against it.
There is something in that formulation. On the small cars the diagonal is not a problem as I see it. On the long cars it is definitely unwelcome. A diagonal is a solution for a small car not a large one. Semantically, a diagonal is indicative of a small car and thus a cheap one. Aren´t car designers supposed to know this kind of thing? I don´t do this for a living so it has taken me a while to analyse the matter. You´d think the craftsmanship people would be up on this an step in to stop inappropriate diagonals.
Richard, what about the rear of the Mitsubishi Lancer Sportback? there’s something there that it’s just not right and maybe it has something to do with diagonal lines (or the size of the C-pillar).
Nothing is troubling my eye in the case of the first or second Mitsubishi. Can you clarify?
The 508 looks worse and worse, though. The cut drove the lamp shape, it seems.
The rear bumper shutline becomes problematic in direct proportion to the height of the belt line (I suppose, divided by length of the rear overhang). Volvo managed the shutline only by making the tail lamps huge in every dimension, shortening the effective height of the bumper.
What do you think of the vertical shutline on Nissan’s U13 Altima/Bluebird? I imagine such a vulnerable body-in-white has led to many a totaled vehicle.
The U13 is a vertical line meeting the curve of the lamps off-normal. That makes a little rat hole at the intersection. Wierdly the sculpting suggests a horizontal gap would have worked quite fine. There are least two distinct versions of that which suggest themselves.