Why Car Tires Are Always Black (And Why The Color Matters)
You can customize the color of your car however you please, but you can't do the same for your tires. They're black for a reason that has nothing to do with style and everything to do with science. The color of car tires comes from carbon black, a fine powder left behind when petroleum products don't fully combust. Most carbon black is made in a furnace by burning thick oil, while some is produced by igniting natural gas, washing down the lining of the furnace, and filtering out the particles.
Carbon black strengthens rubber by binding to the polymer chains, making the compound stronger and more durable. Without it, tire life expectancy would be a whole lot shorter. In his textbook Spectroscopy of Polymers, chemical engineer Dr. Jack Koenig reported that tires made without carbon black might wear out after less than 5,000 miles (tires with it can last 10-12 times that long).
Carbon black also helps dissipate the heat generated by the friction of tires on the road, cutting down on the risk of blowouts. The black color also helps protect the rubber from the effects of UV rays and ozone, both of which can speed up a tire's deterioration.
Have tires always been black?
Tires didn't start out all black. Natural rubber is very light in color, so cars made in the early 20th century often had tires that were entirely off-white. To make them brighter, tire manufacturers added zinc oxide — a less-effective powder than carbon black that still provided some added durability over rubber alone.
As cars got too powerful for the current tire technology, manufacturers began toying with the effects of adding soot to the rubber compounds; this process evolved into the production and use of carbon black. By the 1930s, carbon black-enforced treads were often paired with white sidewalls to create the now-defunct whitewall tire. The stylish touch became less important to buyers after World War II and fully black tires became the standard, although carmakers continued to offer whitewalls through the 1990s on models like the Ford LTD and Chrysler LeBaron. Although they look nice on a luxury or classic car, whitewall tires are notoriously difficult to keep clean,while all-black tires mask all that dirt and grime.
Why tires have stayed black for all these years
Today's tires are a lot more than just rubber and carbon black. They can be made up of over a hundred different materials including steel cords, synthetic fibers, and specialized compounds. With over 90% of the 18 billion pounds of carbon black produced globally each year used in rubber manufacturing, its significant role in tire production is undeniable. It's truly carbon black that has kept tires rolling along smoothly for all these years, and it's also used to make plastics, wire shielding, and printer toner.
Still, there's some innovation happening beyond the scenes and it could take some of the market share away from carbon black. The new kid on the block is silica, and the fact that it can be made from the ashes of rice husks makes it a more environmentally friendly option than carbon black. Continental is one of the major tire brands working with silica, using it as far back as 1994. Only time will tell if increased use of the cream-colored powder over carbon black leads to a change in the color of tires, but the sustainability angle and reduced rolling resistance of silica makes it potentially one of the biggest changes to car tires in the last hundred years.