Team engineers consider the tire's compliance-how it supports the car-as part of its suspension. When a crew chief calls for a change in air pressure, what he is really doing is making a change in the car's effective spring rate. A softer sidewall tire is expected to give teams even more latitude in how the tire can be used for tweaking its handling on race day. "One of the things it does is opens a wide window on car setups," Stucker notes. But the softer sidewall also means that cars will probably have to run stiffer springs. That reverses a trend, which has seen teams reduce front spring rates to about half of what they were a few years ago.
Stucker says that at Homestead, the changes are evolutionary. "The tire is different, but not radically different," he says. "And the tracks remain the same." According to Stucker, teams should be able to go to their notebooks and adjust their settings from last year to come up with a starting point that is pretty close to what they will need for qualifying and race day.
In addition to the new sidewall, the tread surface also will be softer. Tire rubber-from Nextel Cup slicks to what's on your family car-is basically a blend of oils and carbon black. By changing the types of oils and the type and amount of carbon black, a tire can be made to either grip better or last longer. A similar formula, with different ingredients, is used to make the difference between a 60,000-mile, daily-driver passenger car tire and a sticky 24,000-mile, high-performance street tire.
In recent years, Goodyear and NASCAR used a long-wearing compound. Once a tire got up to temperature and pressure, the handling remained relatively stable until the driver simply wore it out. The tires could handle massive loads from both banking and downforce, and failures were rare. "NASCAR has been the key," Stucker says. "It has allowed the cars to evolve to where they have become very aero-dependent. Our tires had to work with that package. The problem is that the cars became so reliant on aerodynamics that the handling changed drastically whenever the downforce was removed."
So NASCAR took some downforce away and Goodyear had to put traction back in. In 2004, with less downforce to keep the cars glued to the track, the new tire will use a softer compound to replace aero grip with mechanical grip. Stucker says Goodyear is also aware that NASCAR can fiddle with spoiler height and other aerodynamic elements all season long, and that Goodyear may have to change tires or tire selection to accommodate the new aero configurations.
Compound Choices
Goodyear has about 18 compounds available and decides in advance which ones it will bring to each track. Tracks are grouped by what type of tire they need. Tracks can move from one group to another as the surface wears out or is renewed.
The tire on Greg Biffle's...
The tire on Greg Biffle's BGN car came apart at Homestead in 2003 so violently that it left team members and Goodyear experts little clue as to the cause.
"Bristol and Las Vegas, for instance, are two tracks being moved into a different grouping because their demands are less severe than others in the current group," explains Rick Campbell, Goodyear's team leader for stock car tire development.
The changes are expected to increase speeds at some tracks where the stickier tires will be used. Cars will use a different compound on the right and left sides. One of the more significant benefits for drivers is that the stickier tires on the left side (which carries less weight through the corners) should grip better and help offset the loose conditions created by reduced rear downforce.
Mongrel Tire
When Goodyear opened its trailers at Homestead for the final Winston Cup race, it unloaded a mongrel tire, a half-breed mix of old and new technology. The tires were built with the newer, softer sidewalls but retained the harder tread compound used during 2003 and prior seasons.