Gentlemen, start your engines! For millions of race fans, those four words evoke emotions and bring families together more than 36
times each year. The sound of 43 stock car engines can be intoxicating. Whether it's the colorful race cars or the more colorful driver personalities, in the United States, The National Association
for Stock Car Auto Racing, better known as NASCAR, is the second-most-watched sporting event behind the National Football League.
NASCAR has three major divisions; the Craftsman Truck Series, Nationwide Series and Sprint Cup Series. While none of the vehicles in the three different divisions look the same, nor do they perform equally, all three groups share one thing in common -- each NASCAR vehicle must use Goodyear Racing Eagle tires.
Since 1997, Goodyear Tire & Rubber Company has been the sole tire provider for all three of NASCAR's top divisions. Goodyear Racing Eagles adorn every Sprint Cup Series car, Nationwide Series car and Craftsman Truck Series truck at every race. Goodyear's exclusive deal runs through 2012 and NASCAR has expressed no desire to allow more than one tire manufacturer into their realm. Formula 1 currently allows for two tire manufacturers to compete for teams, but NASCAR officials fear adding a second tire manufacturer would lead to a tire war. One worst-case scenario of a tire war, and a situation that NASCAR definitely wants to avoid, is one where tire manufacturers build unsafe tires as a result of pushing the limits of tire technology.
As part of their deal, Goodyear works closely with NASCAR research and development officials as well as the individual teams. In fact, during a typical race weekend at a Sprint Cup Series event, NASCAR teams will use more than 2,000 tires. Throughout this article, we'll explain the technology that goes into those tires -- one of the many components that allow NASCAR cars to go so fast and to hold so tight to the track surface. Let's start off by introducing you to the Goodyear Racing Eagle on the next page.
Goodyear Racing Eagles
Goodyear Racing Eagles share many of the same features found in street tires. To see a complete breakdown of street tires, read How Tires Work. However, several components are unique to racing tires and in particular, Goodyear Racing Eagles:
- Apex - controls the stiffness, or rigidity, of the sidewall
- Bead - the area of contact between the tire and the rim (Racing Eagles can have two beads, depending on the track and the tire)
- Carcass Piles - act as the backbone of the tire, providing support and delivering strength to the top of the tire
- Belt Package - Steel braided belts are placed between the tread and piles to give the tire its flat footprint
- Inner Liner - An inner tire that provides support in the event of a puncture or failure to the outer main tire
- Tread Compound - The part of the tire that provides grip -- the contact patch
The most noticeable difference between a Racing Eagle and a Goodyear Eagle F1 street tire is the tread. Racing Eagles have no tread. But don't be fooled. Just because Racing Eagles don't have any tread doesn't mean they lack grip. Racing Eagles are what's known as a slick. Slicks are racing tires with smooth surfaces. The most fundamental method of providing mechanical grip in a race car is to put as much surface area of the tire in contact with the road, or track surface, as possible. Because slicks have no grooves, they have a larger contact patch, or footprint, and provide optimal traction.
A lot of effort goes into building a tire. One of the processes the tires go through involves curing. The curing process gives the tires their desired compound, but racing tires are under an extreme amount of heat and stress at all times and that can change the way a tire grips during a race. As we'll learn later, heat can play a large role in tire performance.
If you've ever watched a NASCAR race before, chances are you've heard the term sticker tires. Sticker tires are nothing more than a brand new set of Goodyear Racing Eagles. The reason crew chiefs, drivers and fans refer to new tires as sticker tires is because of the large data sticker label on the tire. NASCAR teams do not remove the sticker from the tire before they mount them onto the race cars, so when teams turn to a new set of tires, they grab sticker tires. The sticker contains valuable information including spring rate, which is simply another term for tire stiffness, tire code and sequence number. NASCAR teams often try to match tire numbers in sequence to get what they believe to be the most similar tires on the car at the same time. Many teams believe matched tires that come from the same batch will perform consistently together.
In the next section we'll learn how tire testing works and why NASCAR teams are waiting in line to get their hands on Goodyear Racing Eagles.
Tire Testing and Engineering
Goodyear and NASCAR work together to develop tires for each of the three NASCAR series. When Goodyear tests tires, they select certain drivers from each of the four manufacturers in NASCAR and pick tracks they would like to use to acquire data. These drivers bring their own cars and teams and run lap after lap at the designated tracks. Tire engineers record tire temperature and other data to take back to the manufacturing plant where chemists will determine the proper compound to use when they make new tires. A tire compound is a mixture of rubber and polymer chemicals that give tires strength and durability while providing exceptional grip.
Once back at corporate headquarters in Akron, Ohio, Goodyear engineers decide what compound to use for certain tracks. Each racing surface is unique, so Goodyear develops tires that match each venue. For example, tires that have exceptional grip on a rough concrete-surfaced track, like Bristol Motor Speedway in Tennessee, may have poor grip on a smooth asphalt track, like Las Vegas Motor Speedway. It is important for Goodyear engineers to find the right combination in order to build a competitive tire.
Prior to the 2006 racing season, NASCAR teams purchased tires from Goodyear at each race event. Some of the well-funded teams, such as Hendrick Motorsports, Rousch-Fenway Racing (Rousch Racing then) and Joe Gibbs Racing were purchasing more tires than they could use during a race weekend and would often use their excess tires during testing throughout the season. NASCAR officials believed the big teams were getting an unfair advantage through this surplus tire testing method so they implemented a leasing program at the beginning of the 2006 season. Since then, Goodyear has leased tires to every NASCAR team during race weekends. Once the tires are used, the teams return them to Goodyear for recycling. In order to keep track of the tires, Goodyear implants small radio frequency identification, or RFID chips, inside each tire. In addition to race day tires, Goodyear also leases 200 tires to Sprint Cup, 160 tires to Nationwide Series teams and 120 tires to Craftsman Truck Series teams to be used on non-sanctioned tracks for tire testing. The RFID chips allow NASCAR to monitor the testing.
In the past, tire testing was seen as a nuisance by some teams. But in an attempt to equalize the competition and lower costs, NASCAR continues to limit the number of tire tests that teams can conduct throughout the season. Tire tests are suddenly a hot commodity as testing is now at a premium.
By now, you should understand just how important tire testing is to the sport -- but NASCAR drivers want to race, and fans want to watch their favorite drivers push the limits. Up next, we'll go to the track and find out how the teams prepare for race day.
Racing Eagles at the Track
NASCAR teams are made up of engineers and specialists that study every aspect of racing from aerodynamics to, you guessed it: tires. Tires are one of the most important parts of racing and can mean the difference between a win and a bad day. Let's take a look at a typical race weekend leading up to the green flag on Sunday in the Sprint Cup Series.
Goodyear chooses what tire to bring to each race track based on the data gathered from testing and past races. As we've already learned, NASCAR and Goodyear work together to test and develop tires for specific tracks. Some of the tires can be used on more than one track. Goodyear often selects the same tire for tracks that share similar characteristics and configuration. For instance, Infineon Raceway and Watkins Glen are both road courses so Goodyear selects the same tire for both tracks.
Goodyear mounts and balances all tires using a specially designed
tire mounting machine and the teams pick up their tires through the lease program. The Nationwide and Craftsman Truck series have tire rules that limit the number of sets of tires teams can use. In Sprint Cup, there is no limit. Each team has a tire specialist who handles the tire pressures and inspects tires for wear. Teams are not permitted to do anything to the tires once they take possession of them. Teams are permitted to trade tires with other teams but no modifications can be performed. The only adjustment allowed to the tires is an increase or decrease in air pressure. NASCAR teams adjust air pressure to improve the car's handling, which can make a big difference on
Teams typically practice on Friday before a two-lap qualifying session. In general, NASCAR drivers turn their fastest times with new tires. During a two-lap qualifying session, lap times can vary greatly due to tire wear. Drivers normally only take their first qualifying lap as more times than not, their second lap will be slower. Of course, there are a few exceptions. Sometimes the cars don't rely on tire grip as much -- Daytona and Talladega are two good examples.
Engineers from Goodyear measure tire temperature and wear and can make recommendations throughout the practice sessions leading up to the race. In the instance of the 2008 Allstate 400 in Indianapolis, Goodyear officials knew prior to race day that the tires were not wearing properly. Fearing a tire shortage, Goodyear brought in more tires -- tires that were slated to go to Pocono the following week. If Goodyear officials don't like what they see during the practice sessions, they will recommend a mandated air pressure change or advise NASCAR about excessive tire wear due to camber. Too much camber will wear out the inside shoulder of the tire, a condition that can cause a high-speed blowout.
Once the teams are dialed in and Goodyear feels good about the tires, it's time to race. The next section brings it all together as drivers get set to push the limits and reach speeds near 200 mph (321.9 km/h).
Performance on Race Day
All the hard work during testing and practice pays off on race day. Teams can go through as many as 12 sets of tires during a race. Depending on which track the cars are racing on, sticker tires may last a long time or they may fade rather quickly. One thing is certain, a car racing on sticker tires will always be faster than a car with worn tires. Generally, sticker tires are the preferred choice during a pit stop but occasionally teams will put on scuffs or scuffed tires. Scuffed tires are tires that drivers have used for only one or two laps. Scuffs have an advantage in some cases, especially when a driver needs instant grip like during a late race restart. As tire technology advances and Goodyear continues to improve Racing Eagles, scuffs are used less frequently. In rare instances when Goodyear brings an excessively hard tire, as was the case at Atlanta Motor Speedway in the spring of 2008, teams use scuffs to get more grip at the front end of a fuel run or stint.
In tire talk, a stint is the amount of time a tire will be used. Racing tires are designed to be used for a short period of time. Goodyear develops Racing Eagles to last for an approximate distance and depending on the length of the track, stock cars and trucks NASCAR's three major series can run anywhere between 35 and 100 laps on a set of tires. These distances are what the NASCAR teams refer to as fuel runs.
Teams will change tires throughout the race, often choosing to replace tires every time they fuel the car during a pit stop. After the tire is removed from the car, the tire specialist uses a torch to heat up the built-up rubber on the tire so he can remove it and expose three small holes on the tire called wear pins. The tire specialist measures the depth of these pin holes to get indication of how much the tire is wearing, what rate the tire wears and the specific area the tire wears. Crew chiefs use this information to determine what adjustments they need to make during pit stops in order to make the car handle better. Crew chiefs will take all the data as well as input from the driver and tune the car throughout the race. Tires are one of the quickest and most effective areas to tune the car. Tire pressure can greatly affect the handling of the car. A harder tire or a tire with a high amount of air pressure will typically have less grip on the track surface, while the opposite is true for a tire with less air pressure. Sometimes a slight adjustment in tire pressure can give a driver the feel needed to drive straight to the front of the pack.
Tires fail no matter what brand they are. Most of the tire failures in NASCAR are due to punctures from debris on the track or sidewall cuts made during contact between two race cars. When a tire fails at high-speed, not matter what brand it is, the tire will often explode and cause significant damage to the car. Goodyear uses tires with inner liners at high-speed tracks and high-banked intermediate speedways such as Lowe's and Texas Motor Speedways and also at super speedways like Daytona. The inner liner allows the driver to safely control their car in the event of a high-speed failure. The outer tire may shred apart and destroy the sheet metal around the fender, but drivers have much more control on an inner liner than a chewed-up steel rim.
The fastest car doesn't always win. Read the next section to learn why tires fail and how drivers can make all the difference during a NASCAR race. The finish line is just ahead.
Heat and Tire Wear
Racing tires are designed to wear. A well-used tire that is wearing evenly will show uniform abrasion across the entire contact patch. Some tracks act like a grinder or cheese grader on the contact patch of the tire, causing the tire to wear faster. The excess rubber comes off in the form of rubber dust and molten pieces referred to as marbles. The rubber also gets imbedded in the grain of the track. If you have ever watched a NASCAR race and seen the black strip around the track, that's called the racing groove. The groove is nothing more than worn rubber piled on top of more rubber. The groove normally has the most grip on the track but in some cases, drivers will find a secondary groove to drive in because the excess rubber will actually hamper the handling of their car. The marbles accumulate toward the outside wall of the race track and can be a very slippery place to drive. How can more rubber be slippery? Just as the name implies, the small rubber balls act like marbles underneath the tires, causing the cars to slide.
Tires also go through heat cycles that can change the grip of the tire. In general, a tire will get harder after each heat cycle. Experienced drivers take care of their tires and don't allow them to build up too much heat. A more evenly heated tire will go through less heat cycles and will have optimum grip for a longer period of time.
All but four races in the 2008 NASCAR Sprint Cup racing season take place on oval tracks. Because of the high banking on several of the tracks, stock cars and trucks in NASCAR's three series can reach speeds approaching and in some cases, above 200 mph (321.9 km/h). Centrifugal force allows the cars to reach the high speeds, but as you can imagine, the tires wear out very quickly. Tire wear is good and bad at the same time. NASCAR teams don't like tire wear because the cars are slower on worn tires; however, proper tire wear is crucial to tire safety. If a tire does not wear properly, the rubber can vulcanize or cure. Racing tires are not completely cured when they come from the manufacturer. Because of the excessive heat generated by high speeds and significant g-forces, engineers leave part of the curing process to happen during the tire's use. Tire engineers understand the heat will change the composition of the rubber so they plan for the on-track vulcanization process. This is why it's important to acquire accurate data during tire testing.
For more information about tires, NASCAR and other related topics, follow the links on the next page.
Related HowStuffWorks Articles
More Great Links
- Gibson, John. Stock Car Racing Magazine. "Racing Suspension - Tire Stagger." (Aug. 10, 2008) http://www.stockcarracing.com/techarticles/scrp_0805_tire_stagger/index.html
- Goodyear Blimp official website. (Aug 16, 2008) http://www.goodyearblimp.com/
- Goodyear Racing official website. (Aug. 12, 2008) http://www.racegoodyear.com/
- Inside Racing Technology. "The Racing & High-Performance Tire." March, 2004. (Aug 13, 2008) http://www.insideracingtechnology.com/tirebkexerpt3.htm
- Kelley, Dick. Stock Car Racing Magazine. "NASCAR's Rain Tire: The saga of a tire in search of some water." (Aug. 12, 2008) http://www.stockcarracing.com/techarticles/1589_rain_tires_good_year/index.html
- NASCAR.com. "Goodyear sets forth a plan to address NASCAR tires." Aug. 2, 2008. (Aug. 10, 2008) http://www.nascar.com/2008/news/headlines/cup/08/02/goodyear.actions.indy/
- O'Connor, Mary Catherine. "Goodyear Using RFID for NASCAR from Cradle to Grave." RFID Journal. July 19, 2006. (Aug. 13, 2008) http://www.rfidjournal.com/article/articleview/2500/1/1/
- Packman, Tim. "Tech Q & A: Rob Lopes." NASCAR.com. Nov. 7, 2002. (Aug. 12, 2008) http://www.nascar.com/2002/kyn/tech/qa/11/07/qa_lopes/index.html