The evolution of colored smoke tires.

The contribution of tires to motor-sports competition is well known, as tire producers often make special tires to perform competitively in various types of events. The real purpose of motor-sports and various other sports is entertainment, thereby giving a chance for sponsors and vehicle equipment suppliers to advertise their products. The motor sport of drifting is unusual in that the speed, or "who gets there first" is not the objective. Style points are awarded to contestants based on how well drivers can control their high horse-powered cars while sliding around comers. The sliding tires invariably produce clouds of white smoke as the tread rubber "bums off" and condenses into solid particulates. Kumho engineers and sales personnel observing one of these drifting events proposed that if one could make tires that produced a colored smoke, that entertainment value would be enhanced significantly. This led to a project at the Kumho Development Center in Akron to attempt to color the smoke emanating from skidding tires.

With the growing popularity of motor sports, more tire manufacturers participate in sponsorships to gain the benefits of showing their technical capabilities by producing tires for these highly competitive events. Not only are there large live audiences witnessing these events, but also media coverage through major network and cable TV channels, such as the Speed Channel, providing coverage for the enthusiast. Also, not to be ignored is the huge amount of exposure that can be obtained through the internet. Bloggers often discuss tires and others products by brand name, thereby generating a significant amount of free advertising. Smaller companies can especially benefit from this increase in brand awareness.

Origin of the concept

Kumho motor sports engineers and marketing personnel were awed when they first witnessed the increasingly popular sport of drifting, where drivers are judged by how well they can control their high horse-powered, rear wheel driven vehicles as they spin the tires around comers while driving at high speeds. The tires create large volumes of smoke as they bum off through degradation of the tread rubber. The tires, as one can imagine, are worn out rather quickly in these events. Although the sport is gaining in popularity, not many drivers have the special driving skill that is needed.

More than two years ago, as engineers and sales personnel discussed the sport of drifting during a product meeting, one of the engineers half jokingly asked: "What if the tires emitted colored smoke?" The new concept was then given to the chemists in Akron to develop.

Search and discovery

When first hearing the idea, we admittedly did not take the request very seriously. The concept was outside the field of our compound development paradigm. Raw material challenges presented to tire compounders are aimed at improving grip, treadwear, rolling resistance, handling, cut-chip, ease of mixing, faster curing or cost reduction, but coloring the degradation products of rubber was not in our play book. We knew of no one who was knowledgeable on this subject. We ignored the project for a few weeks, then initiated a Google search for colored smoke. This led to a call to a California-based special effects company. When the expert was asked if some of the special formula for smoke grenades could be added to a robber tire tread compound, he flatly told us that it would not work. They evidently would employ a type of colored smoke grenade often used by the military for signaling. These are comprised of a low temperature pyrotechnical composition mixed with one of a variety of smoke coloring dyes. When they are used, a licensed pyrotechnics user must be present.

We then turned our focus to the smoke dyes themselves, and contacted a manufacturer. The smoke dyes function by sublimation at a temperature of nearly 400[degrees]F. The resulting vapor colors the solid smoke particulates, and colors them as cooling and solidification takes place. What if we just added some smoke dye to the tread rubber? Would the spinning, skidding tire reach sufficient temperature to initiate the sublimation? Would the dye vapor be trapped in the rubber or would it diffuse through the rubber? Would enough surface rubber be burned or degraded? Would enough dye be present to color the resulting smoke particles? How could we test the concept in the lab? Another potential obstacle was that the dyes are quite expensive, nearly $30 per pound. The various colored dyes involve various chemistries and do not all sublime at the same temperature, so we asked a dye manufacturer for a sample of the dye that sublimed at the lowest temperature. It was the red dye 1-(N-methylamino)-9,10-anthraquinone.

Lab trials

After receiving a sample of the red dye, we decided to mix some into a typical performance tread compound. At first, we added about five percent by weight. We then obtained our standard physical properties. The dye basically increased the hysteresis, resulted in a higher durometer and reduced lab abrasion by about ten percent. But how do we test for colored smoke emission? We took some cylindrical buttons used for dynamic testing and held them against our grinding wheel with firm pressure to generate smoke. As the pellets smoked, a reddish hue began to emerge from the grinding wheel! It was not intense but we were encouraged.

Tire tests

The next step was getting the approval to purchase ten pounds of red dye at $30 per pound so that we could mix some dye into a rubber compound and have some tires retreaded. We asked a retreading company to send us some of their tread rubber and decided to add the dye to the rubber on a mill at a level of 10% by weight, in the hope of intensifying the smoke color.

We took the rubber compound to a local rubber processor to have the rubber coated and slit into strips to accommodate the retreading. We noticed during the process that the slab dip turned pink. We also noticed staining of the conveying belts. This raised a red flag of concern with our future plans to produce tires in our production plants. We had the tires retreaded and then shipped back to Akron. The treads were bright red, but the red bloom could be wiped off rather easily.

We had the tires mounted on the company van, pinched off the brake lines and began to spin the tires. At this point, no one really knew what to expect. In the lab trials, we only saw a wisp of pink smoke coming off the grinding wheel, and the lab pellets wore out rather quickly. As the tires spun, we began to notice a bit of red colored smoke around the wheel wells. As the rpm increased and the tread surface got hotter, clouds of red smoke began to engulf the vehicle. Over the roar of the revved-up engine, I could hear a few cheers from the few Kumho employees who had gathered to witness the trial. Amazing, I thought. This actually works.

Later, we ordered some blue colored dye and had a few more retreads made. Our next trial included a blue smoke tire on one drive wheel and a red tire on the other side. Smoke had hardly been noticeable in grinding wheel trials on buttons containing the blue dye, but on the vehicle, an intense cloud of blue smoke billowed from the wheel well on one side, and red emanated from the other. A purple hue appeared over the vehicle as the colors merged.

Drifting debut

We purchased enough dye to build tires in Korea. Our motor sports engineer contacted a drift team (Enjuku) that competed in the Formula D circuit. After testing our special tires, they enthusiastically welcomed the opportunity to debut the Red Smoke Tire at the April 2005 Formula D Drifting event in Atlanta. The Formula D events were also aired on G4 TV.

Kumho Ride and Drive

At Kumho's Ride and Drive event in June 2005, Kumho introduced a new high performance tire, and journalists from several magazines were present. The event was kicked off by two sports cars spinning and skidding, doing donuts on the track. One sports car was equipped with both red and blue colored smoke tires. The bizarre spectacle resulted in significant free advertising for Kumho, as articles and photos were included in several web sites and magazines in the next few months.

Ford auto show 

Following the June event, we took the colored smoke tire road show to Carlisle, PA, and entered the "burn-out" contest at Carlisle's Ford Auto Show event. Factory Five, which sells do-it-yourself Cobra-styled auto building kits, entered one of their custom-built Cobras, with colored smoke tires on the rear driven axle, in the "burn-out" contest. The result was more valued exposure for the Kumho brand, as the tires billowed red and blue smoke clouds. A "Cars of Carlisle" TV program airs once per year on Speed Channel, and one of their programs covered the colored smoke burn-out.

Manufacturing issues

As with many new concepts, the colored smoke tire is not without its special manufacturing issues. As the tread is processed, the dye blooms to the surface and stains the slab dip, conveyor rolls, processing equipment and the mold surfaces. This results in new housekeeping tasks that are certain to hamper productivity. Attempts to address this, including dye encapsulation, have thus far not been successful.

Physical property adjustments

Lab trials adjusting the polymer blend by increasing BR and reducing SBR resulted in recapturing the loss of tread wear, while traction is equal to the control recipe without smoke dye.

Summary

Colored smoke dyes can be added to tire treads to color the smoke generated by the high speed spinning of tires against paved road surfaces, provided that dye sublimation temperatures are reached in the tread surface. This has been accomplished by mounting tires on the rear axle on rear wheel drive vehicles. The color intensity is proportional to the amount of dye that is added and the temperatures that are generated. Physical properties will be affected, resulting in faster tread wear and higher tread compound hysteresis, but traction may be enhanced. Housekeeping issues in the manufacturing plant have hampered wide-spread production of these tires, due to color staining of processing equipment, molds, etc. Other techniques are being explored.

Nevertheless, the colored smoke tire has been a successful marketing item for Kumho, and has the potential of being a high profitability product, assuming that housekeeping issues during manufacturing can be addressed.

This article is based on a paper presented at a meeting of the Rubber Division, ACS.

Passenger tires with orange, lavender and jasmine scents

Kumho Tire USA has also introduced the world's first fragrance automotive tire, the ECSTA DX. The project is the fruition of more than a year's worth of research and development to deliver an alluring aroma tire that replaces the normal black rubber smell with heat-resistant oils in the scent of lavender, and in later versions, neroli (orange) or jasmine. Visitors to www.kumhotireusa.com can find the nearest dealer.

According to Rick Brennan, brand director for Kumho, the company is selling the DX aroma tire to help build brand awareness and highlight Kumho's tire technology expertise in the highly competitive automotive marketplace. The tire is targeted at female consumers who drive such sedans as the Honda Accord, Toyota Camry, Subaru Outback, Chrysler Sebring and Ford Taurus.

In addition to a unique aroma, the ECSTA DX is engineered to deliver low noise levels and ride characteristics on par with the leading tire brands. Ride comfort is maintained throughout the life of the tire through the use of tread elements designed to provide uniform linear stiffness. Optimized pitch sequence and variable pitch lengths help minimize noise, while a straight center rib provides high-speed stability.

The DX features four wide grooves that help evacuate water, while a silica compound improves all-weather performance and wet traction. High tensile steel belts and a jointless nylon cap ply also help improve noise, ride comfort and durability, while an undertread reduces unwanted heat buildup for consistent performance.

The ECSTA DX Aroma tire will be sold starting in the first quarter of 2007 in three sizes: 205/60R16 (MSRP $119), 215/60R16 (MSRP $125) and 235/60R16 (MSRP $138).