February 2008: "Black just looks good"

In effect, car tyres could be red, green or blue. Holger Lange, Head of Material Development for Passenger and Light Truck Tyres at Continental, explains why we still only see black tyres on the roads and why tyres of different colours are even prohibited in Los Angeles.

ContiSoccerWorld: Mr Lange, cars come in every colour imaginable – why do tyres only come in black?

Holger Lange: Traditionally, tyres are black because of the percentage of carbon black in the rubber. Although the very first tyres were not black at all. Originally, tyres were a brownish colour due to the colour of the natural rubber from which they were made. I can remember during my chemistry degree, on the first day of the ‘organic chemistry’ course, our elderly professor proudly showed us a black and white photo of the first car with rubber tyres – a vehicle owned by Kaiser Wilhelm. It was clear from this photo that the tyres were not black but a lighter colour – at the time, this really surprised me. These were tyres that had been made before carbon black was introduced into tyre production. Carbon black was first used in 1926 and was the reason for the black colour of the tyres. The colour was purely a side effect, however – carbon black was introduced because it enhanced the pliability, durability and abrasion resistance of the rubber. Vehicles were becoming faster, which of course put greater demands on the tyres. This was the first milestone in tyre development.

ContiSoccerWorld: Today, rubber is made pliant using silica rather than carbon black. Does that mean that it would now actually be possible to produce colourful tyres?

Holger Lange: That's quite right. Until the 1990’s, carbon black was technically essential for producing sufficiently abrasion-resistant tyres. Today, however, we are able to replace the carbon black with silica to such a degree that tyres no longer inevitably have to be black. You only need two to three per cent of carbon black to make a tyre black; but this quantity is no longer technically essential. In principle, you could manufacture tyres without carbon black and there would be no impact on performance. Silica itself is colourless, meaning that we could include any conceivable colour into the rubber mix and produce tyres in all the colours of the rainbow.

ContiSoccerWorld: Why do you not do it? We still only see black tyres on the roads.

Holger Lange: There are many different reasons for this. For one thing, you would need tyres in the appropriate colours for all the different car manufacturers, and today, each manufacturer has its own, highly varied colour palette, which would mean that we would have to produce such a variety of tyres that mass production would become much too expensive. Another thing is that you cannot simply paint a tyre. Dying the outer layers of rubber would not be sufficient either. The colour would not last long enough and you would want a red tyre to look as good after 5,000 km and 50,000 km as it did on the day it first rolled off the production line.

ContiSoccerWorld: Could you not dye the rubber completely for special models?

Holger Lange: Yes, that would certainly be possible. We already make colourful bicycle tyres for instance and once made a collection of magenta-coloured tyres for the Deutsche Telekom team. Today, bicycle tyres come in all conceivable colours. Producing colourful car tyres, however, would require considerable expense. At the moment, incidentally, there is actually a green prototype tyre in the corridor just outside of my office; but to produce a range of such tyres, you would have to completely dye all the rubber compounds of the individual tyre components (the tread strip, the different rubber compounds of the sidewall, the beaded rim and so on). These rubber compounds, which are made to a variety of different recipes, would all have to have the exact same colour; in principle, the recipes would all need rewriting.

ContiSoccerWorld: But what if a car manufacturer were prepared to contribute towards the cost?

Holger Lange: Anything is feasible; but what has to be understood is that it would also require a major restructuring in terms of production. You would only be able to do something like this in the summer holidays when tyre production tails off somewhat. To do something like this, you would effectively have to perform an entire factory reset. All rubber processing machinery would have to be emptied and replaced with the colour variety. And vice versa once you had completed the run – you can’t produce transitional colours; for instance, we don’t want the entire next series of winter tyres to be tinged green (laughs). And even if you do produce a green series, as we did, not all problems are eliminated. The green tyre on our corridor is just now beginning to reveal one of the major problems with colour tyres; discoloration – it has only been there for about six months and already you can see the green changing colour.

ContiSoccerWorld: Really? So you haven’t yet perfected the art of manufacturing colour tyres?

Holger Lange: I wouldn’t say that. In principle, tyres are actually supposed to change colour. The effect is caused by the fact that a tyre is required to brave the most adverse conditions over its entire lifetime;  it is constantly exposed to sunlight and air containing ozone, and may also have to put up with cold temperatures without complaint. For this reason, the rubber of every tyre is treated with special antidegradation agents and antiozonants. The antiozonants for instance have a slight brownish colour and should gradually emerge onto the surface of the tyre rubber over time in order to protect it. This occurs as a result of diffusion and everyday wear of the tyre when in use. However, this causes the surface of the tyre to take on a slight brownish tinge, which can also be observed with black tyres. If you look at the rubber from an angle, you may occasionally notice a slightly yellow or bluish discoloration as a result of precisely this protective wax. With colour tyres, this discoloration is even more noticeable because these additives are not currently available in the different colours. And as a result, the tyre stops looking so great.

ContiSoccerWorld: And yet some tyre manufacturers do keep trying to bring out colourful products. A few years ago, a competitor really did market green and blue models, but stopped production on account of low demand. Perhaps drivers don’t actually want colourful tyres?

Holger Lange: Tyre customers are certainly very traditional by nature. Black tyres suit every vehicle – they simply look chic. It’s a bit like with shoes – most people wear black shoes; you don’t see people wearing red or green shoes so much. Black is also practical. If you have a lovely yellow tyre and you drive through the mud, it’s not going to look so lovely afterwards.  The dirt is not so noticeable on black tyres.

ContiSoccerWorld: There are some drivers, are there not, who tend to only take their cars out when the weather is nice. Perhaps they would appreciate a few colourful, eye-catching tyres - a niche market maybe?

Holger Lange: A few years ago, one of our US competitors did actually successfully market colour tyres in California. It’s an interesting story. At the time, I myself was in Los Angeles and my job as the Head of Technical Benchmarking was to monitor the market to discover what technologies our competitors were using and any new and upcoming trends. Some of the tyres made by this manufacturer came with optional blue or red tread strips. Coincidentally, however, blue and red were also the colours of two rival South Central LA gangs. As a result, the gangs used the tyres to mark out their territories; they would skid across the roads to indicate the line over which the rival gang was not permitted to cross. Many of the roads over there are covered in a light-coloured concrete, with the result that the markings were highly visible. As a result of this, the mayor of Los Angeles called for the tyres to be banned.

ContiSoccerWorld: That must be the worst possible scenario in marketing terms, wouldn’t you say?

Holger Lange: I’m not sure I could say that. There’s a theory that any publicity is good publicity. Following this, the tyre was known throughout the entire US – which can’t have done the brand itself any harm. Although of course you can never predict something like that and certainly wouldn’t want to provoke an incident of that kind.

ContiSoccerWorld: Would you not also say that colour tyres are another way of making a uniform product stand out from the rest? Any non-experts looking at a tyre would need to look very closely to determine whether the tyre in front of them was a Conti, Michelin or Goodyear tyre.

Holger Lange: Yes and no. Of course, a need to distinguish your brand from the rest does play a role in such marketing considerations. On the other hand, performance is the most important distinguishing feature when it comes to tyres. A tyre must be safe, brake well and, at the same time, have the lowest possible rolling resistance… If we are able to communicate excellent results and the customers are happy with our products, then we do not need blue tyres to set ourselves apart from the competition. There are also distinguishing features in terms of design. For instance, the tread pattern of every tyre is different, as is the design of the side wall. At Continental, we have developed a special moiré pattern consisting of fine lines to ensure that Continental tyres are distinguishable as such even from some distance away. When out and about, as far as I am concerned, it is predominantly the side wall of the tyre that you notice – when cars are parked one behind the other at the side of the road for instance. With this in mind, it is not at all necessary to dye tyres red, blue or green.

Contact:

Alexander Lührs

Head of PR – PLT Tyres

Continental AG

Büttnerstraße 25 , 30165 Hanover, Germany

Phone: +49 511 938 2615

Fax: +49 511 938 2455

E-mail: alexander.luehrs@conti.de

Internet: www.conti-online.com

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