New tech and trends in performance tires

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By SEMA's Steve Campbell...

The average consumer doesn’t devote a lot of thought to tires until its time to buy a replacement set. Even then, the tendency is to make a direct swap back to what came on the car from the dealership. But performance enthusiasts are a different breed. They actually care about tread patterns, rubber compounds and aspect ratios, and they may not be quite so concerned with how many miles a set of ultra-high-performance (UHP) tires are going to last compared with how well they’ll stick in a decreasing-radius turn.

Performance tires don’t undergo wholesale redesigns or revisions at a very rapid rate. The current offerings have taken quite a long time to develop, and there just aren’t that many startling new developments in the performance-tire marketplace. Still, we wanted to take a look at the segment to see what’s new, and so we contacted the largest of the companies who offer products in the category.

Perhaps the most pervasive new technology in the tire marketplace, whether high performance or not, is the use of pure nitrogen as the inflation medium. Because the nitrogen molecule is significantly larger than that of oxygen, it doesn’t seep out of rubber compounds as quickly as normal air does. That allows more consistent and longer-lasting inflation pressures, theoretically also providing longer wear and better fuel economy as the tire maintains its footprint, reduces sidewall flex and reduces running temperatures.

“Probably the greatest help nitrogen can provide to the average driver is that it dissipates more slowly through the inner liner and tire than air and therefore assists in maintaining inflation pressure,” said Phil Pacsi, executive director of consumer tire marketing for Bridgestone/Firestone. “It is the inflation pressure in the tire that carries the load, so a loss of pressure translates into a loss of load-carrying capacity. That can result in overloaded tires and tire failure, so this is very important for the average driver.”

Toyo sponsors the Speed World Challenge racing series, and Proxes tires are used in the Touring and GT classes. The tires are filled with nitrogen—a trend in both racing and in street-performance tires—which provides more stable inflation pressure. For performance applications, however, nitrogen inflation may provide even more significant benefits.

“Primarily because it is a dry gas, nitrogen also reduces pressure build-up due to operation,” Pacsi said. “Air typically contains water vapor, which will increase the pressure in a tire three to seven psi as it is heated, depending upon driving conditions. Because nitrogen contains basically no water vapor, the pressure build-up due to heat is minimized. Therefore the tire’s hot pressure is very similar to the cold-inflation pressure, with much less input from the driving conditions. That means enthusiasts can set a cold pressure and more accurately predict the hot pressures, regardless of usage conditions.”

Frank Secondari, product development engineer for Kumho Tire, concurred that nitrogen can play an important role in racing and other high-performance applications, but he’s not convinced that it’s worth much in a normal street application.

“You see much more benefit if you’re either going to be racing or you have a tire whose carcass is going to run for an extremely long time,” he said. “A long-haul truck tire that runs 100,000 miles, for instance, will probably see advantages. In a passenger car, where you’re going to run 30,000 or 40,000 or 50,000 miles, it’s probably not that significant.”

The fact that nitrogen produces less temperature change in a truly high-performance environment has led many competitors—both professional and amateur—to embrace the technology. In the Speed World Challenge series, the cars sponsored by Toyo Tires in the Touring and GT classes compete on Proxes RA-1 tires filled with nitrogen because inflation pressure doesn’t increase quite so much as with air. But Earl Knoper, a consultant to Toyo, believes that more commonplace applications can benefit in other ways.

“Nitrogen is also corrosion resistant inside the tire and wheel,” Knoper said. “It will keep the bead area cleaner because there is hardly any corrosion at all with nitrogen.”

Bridgestone recently introduced Ever-Black sidewall technology, currently available only on the Dueler H/L Alenza. The new combination of additives retain a sidewall’s shiny black appearance without the need for sidewall dressings that tend to bleach the elements that protect against ozone. Keeping inflation constant may mean more to the ultra-high-performance market than to the street vehicle, but steady pressure is also key to optimal fuel economy. In the last year, we have seen wildly fluctuating fuel prices, and while costs have mitigated recently, gasoline will never again be as cheap in the U.S. as it once was. And while fuel economy and high performance don’t really go together, maintaining proper inflation pressure is one way to make a difference, however slight.

They say that the best rolling resistance—the tire characteristic that relates to vehicle fuel economy—is a steel wheel running on a steel rail, as on a railroad car. The reason is that there is no deflection in either the wheel or the road surface. When something deflects, it generates heat, like bending a paper clip a number of times quickly. The heat comes from the energy that is delivered to the tire and the road to move the car forward.

“A tire deflects more if it gets hotter, and more of the engine power is used in that heating, yielding less to move the car,” said Pacsi. “The most visible form of deflection in a tire is the sidewall, but actually most of the tire’s rolling resistance comes from the tread area. A softer tread compound—one that can really grip the road for better traction and performance—will deflect more than a harder compound, generating more heat and using up more of the engine’s power. So the best ultra-high-performance tires are typically not the best for fuel economy.”

In the case of the auto manufacturers and the tires they deliver on showroom-stock cars, however, the tires must contribute to fuel-economy numbers on the window sticker that will appeal to consumers. Thus, the OEMs will sometimes re-prioritize performance characteristics to achieve some level of fuel economy, and that means that the best fuel economy performance tire available will be the OE tire, Pacsi explained.

Going from one performance category to the next may not show much fuel-economy change, but going down in size will, said Secondari. “If you downsize tires considerably—if you replace 225R50-16s with 185R65-15s—you should very clearly be able to measure an improvement in fuel economy during day-to-day driving. Obviously, you’re also going to be able to feel a loss of performance.”

In the real world, however, consumers are not reducing their tire diameters, and they’ve actually increased wheel diameters dramatically in the past few years. Where 14- and 15-inch rims used to be the norm, they’re now up to 20 inches or more in some applications. That means a significant reduction in the sidewall height to maintain the same tire diameter.

“Most OE tires, regardless of their rim diameter, have an overall diameter of 25 or 26 inches, and that’s because spindle height on the car has to remain about the same as it has traditionally been,” said Toyo’s Knoper. “So as you increase rim diameter, you decrease the aspect ratio and still come up with the same overall diameter of the tire—about 26 inches. I can’t see that the manufacturers are going to increase the overall diameter too much, because that changes the ride height of the car. And I can’t see that OE is going to go to a much lower aspect ratio than they’re using now. Most of them are in the 55, 50 and 45 aspect range because they want to have some kind of ride comfort. If you go much lower than a 45 aspect ratio, you’re really sacrificing comfort.”

One recent innovation from Goodyear is the use of volcanic sand in tread compounds of TripleTred Technology tires. Goodyear representative said that the company has other new technologies that will be unveiled in 2006, so we’ll keep our ears to the ground. Bob Toth, Goodyear’s marketing manager for auto tires, said that the marketplace will always be the major factor in where tire sizes go. “Additional sizes are always possible,” he said, “but changes in wheel diameters are driven by consumer needs. High performance can mean many things. As examples, Toyota has a Camry with 17-inch, V-rated tires as an OE fitment, and Ford has a pickup that comes on 22-inch OE tires.”

Secondari also sees limits to tire size for pragmatic reasons. “The limit is driven by the weight of the vehicle more than anything else,” he said. “I don’t know what the upper-end limit is going to be for passenger cars. It’s really a matter of what they design the vehicles to handle, so that’s driven by the auto manufacturers.”

Consensus among the experts seems to be that tire diameter will grow slightly or remain about the same, regardless of wheel size. However, wider tires with reduced sidewalls seem to be a steady trend.

“On the aftermarket side, we’re recommending that you don’t change the overall diameter of the tire for Plus 1, Plus 2, Plus 3 and Plus 4 fitments because you’ll change the handling of the car,” said Knoper. “We recommend that you stay within 3% of the original-equipment overall diameter, and we also recommend that you stay within 3% of the original tire’s load index.”

Knoper pointed to tire-pressure monitoring systems (TPMS) as the most significant change to the market in recent years. TPMS will be required on all new vehicles under 10,000-pound GVWR by 2008, and it has already created a stir throughout the tire and wheel industry, including on the specialty-equipment side.

“That’s something that the aftermarket people will need to deal with,” Knoper said, “because if you’re putting on Plus fitments, you might not have room in the wheels for TPMS. Although the government regulations do not insist that the specialty-equipment conform to TPMS, I think that most drivers would like to retain their TPMS when they replace their tires.

Bridgestone/Firestone’s Pacsi said that the industry continues to grow in selected areas, including high performance (HP), ultra-high performance (UHP) and highway light-truck and SUV tires. He felt that mass market and cosmetic performance tires are on the decline as more HP and UHP tires are provided as original-equipment fitments, and Secondari also said that raised white letter tires are history except for the vintage-car market. Pacsi noted that run-flat tires will continue to see increases in the marketplace as they are provided from the factory and consumers gain awareness of them. In fact, Bridgestone recently shipped its 3 millionth run-flat tire.

“We’re increasing the number of product niches,” Secondari said of Kumho’s offerings, “and the buyers are getting pretty sensitive to that and are starting to look for tires that are in the niche that they really want. An example would be ultra-high-performance tires. Fifteen years ago, it was basically one niche—the UHP. Now the ultra-high-performance market has fragmented, and you have a general-purpose UHP, an all-season UHP, a UHP lapping-day tire and a UHP high-speed tire. There are probably at least five niches.”

The lapping-day tire is a relatively new term in the industry. Secondari said that there is a distinct market developing for very high-end performance street tires—something that is a street tire but is also very capable and competent on a race track.

“A lapping-day tire is for somebody who has a car he drives on weekends and takes to the race track two or three times a year just to sharpen up his driving skills,” Secondari explained. “It might not be an ultimate race tire, but it performs well on the track.”

Knoper said that Toyo has also seen changes in the market that incorporate more offerings in the performance ranges. The company is in the process of completely revamping its broad-line tire offerings, which are the first replacements for OE tires. “The traditional H-rated or non-speed-rated tires are just not being equipped on cars any more,” he said, “so our traditional broad line is now going to be kind of a comfort ride ultra-high-performance line to accommodate the new sizes and speed indexes that are being fitted on cars.”

Kumho has long been involved in the performance realm, but the company has also developed one of the more entertaining tire technologies we’ve seen in a while. Kumho’s colored-smoke tires were developed specifically around the drifting market, where a part of the show is burnouts and smoke-generating slides.

“The drifters can have tires that blow off not only white smoke but also blue, red and yellow,” Secondari said, “and the kids love that type of stuff.”

It gives a whole new meaning to the term “colorful performance.”