Tire management holds race results in the balance
Even the fastest cars can be made useless if tire performance is poor or the pit crews don't manage the tires properly.
When you hear the television commentators discuss "tire management" during a NASCAR Nextel Cup race broadcast, they are talking about the driver not abusing his tires by sliding through the corners or overbraking going into the corners and elsewhere. This would create too much heat that will impact the tire's performance.
It actually starts many months before a race when engineers at Goodyear in Akron, Ohio, begin formulating precise rubber compounds that will be used to make the tires for a specific race at a designated track. Tires can be made as hard as concrete or as soft as bubble gum. The Goodyear engineer's job is to formulate and make a tire that will maximize grip or adhesion (soft) between the tire surface and the track surface while also providing acceptable surface wear and safety (hard).
Two different formulas must be developed for each race because Nextel Cup race cars run a different compound in their left side tires than in their right side tires. If you are turning left on an oval track then you are creating more downforce and lateral pressure on the right side, causing more stress and wear on that side.
Goodyear engineers perform test sessions on new tire compounds with selected Nextel Cup teams to gain their input and confirm that the tire will perform according to their calculations. Knowledge gained from these test sessions is then passed on to all of the teams to aid them in the setup of their cars.
Tires are the most critical component of a race car. They are the only part of the car that (hopefully) makes contact with the track. You can have an engine with twice the horsepower of your competitors, but if you cannot transfer that power to the track it is useless.
All of the complicated calculations that are made during the setup of a race car -- spring and shock selection, front end geometry settings, chassis rake and tilt, etc. -- relate to managing tire patch and slip angle.
Tire patch simply refers to the amount of the tire's surface that makes contact with the track. When the driver turns the steering wheel, he creates slip angle by flexing the side wall of the tire. Slip angle is the difference in direction between the center line of the tire that is being turned and the direction of the tire patch that is contacting the race track surface. If the slip angle is exceeded during the turning process then the tire will slide across the track surface causing added friction and unwanted heat. If a reliable tire patch is not maintained then the car's steering will feel erratic and uncomfortable to the driver.
You will often hear a driver say, "We missed the setup" when referring to a ill-handling car. Teams will constantly adjust the setups on the cars during pit stops to either change or maintain a car's balance and tire patch for maximum grip. Adjusting air pressures manipulates tire patch and can either tighten up or free up a race car as needed. While Goodyear recommends a minimum tire pressure, many teams will ignore that recommendation to gain grip. If the right front tire blows out then it is a probability that recommended tire pressures were not followed or the driver repeatedly exceeded the slip angle and created excessive tire wear. The tires were not managed properly.
You can see slip angle being created by turning the steering wheel on your family car while it is sitting still. Watch the sidewall flex or distort as the turning wheel pulls the tire tread in the direction you are turning the wheel. You may even hear the tread slipping across the pavement as you turn the wheel.
Teams strive to achieve a "neutral" balance in a race car to equalize tire wear and create favorable handling characteristics for as long as possible. "Neutral" simply means the car is balanced front-to-rear and from side-to-side. However, the laws of physics and NASCAR rules make "neutral" a difficult condition to achieve.
A driver can increase the front tire patch and the turning ability of the car by how he drives it into a corner. On banked tracks the front springs will naturally compress as the driver turns into the corner banking and decelerates. It creates added downforce or load as the car's weight shifts more to the front.
Braking can also increase downforce, which increases tire patch in the front by compressing the springs even more, thus helping the car to turn. Conversely the driver can increase tire patch in the rear by how he accelerates off the corner. He can literally drive the car off the corner with the accelerator. If done properly and consistently then he is managing his tire wear during the race.
Car balance changes and the track surface can change as a race progresses. For example, as fuel is burned off the balance of the car shifts forward and it should become tighter. A properly set up race car will allow the driver to compensate for this change and maintain a competitive lap speed. When you hear a commentator say a particular car is better on long runs or another car seems to lose its handle after a few laps, he is saying the car that handles on the long run is set up to compensate for the fuel burn off and tire wear while the car that is good on short runs but falls off quickly is set up to take advantage of new tires. How a team anticipates a race to unfold plus their driver's individual style of driving will influence how they set up their race car. Expect a lot of cautions? Then you might want to set up for shorter runs because you will be able to keep fresh tires on the car.
Each Nextel Cup track is different in design, layout and track surface composition and therefore provides a vast array of challenges for the engineers to overcome if they are to provide a safe and reliable tire for competition. As an example, tracks such as Martinsville and Dover have concrete surfaced corners that cause different wear and grip concerns than if they were blacktop.
However, Dover has much higher banking in the corners than Martinsville, which is basically flat. And Dover is a mile-long track where Martinsville is only a half-mile long. Each of these variance creates a new set of problems to be overcome for both the Goodyear engineers and the teams.
A track such as Darlington that was built more than 50 years ago presents different challenges because of its shape (egg) and the track surface. The paving contractor used shell rock in the black top mix when Darlington was paved many years ago. As the blacktop has been worn down over the years the shells have become exposed and are like sharp little razors sticking out of the track surface. Add in the fact that the Darlington track was built in a sandy area of South Carolina, meaning sand is constantly sifting onto the track, and you have created one very abrasive racing surface that eats up tires quickly.
There is an old saying in racing: "Slow down and go faster." That means a race car kept in balance throughout the lap by not overdriving it will be quicker for a longer time because the tires are not being overworked.
Nextel Cup races are much different from a typical Saturday night short track race. Tire management is not nearly as critical for the Saturday Night racer. He might only run a limited number of laps on his tires during a complete race whereas the Nextel Cup driver might drive hundreds of laps before he pits. The better he manages his tire wear the more he can expect to get out of his race car during a long green run.
The successful Nextel Cup driver has to learn how to control his speed for long periods of time to minimize his tire wear and maintain a competitive speed. He must learn to adapt his driving style to different track sizes, shapes and racing surfaces to be successful. And it all relates to the tires.
Bill Borden is a former championship winning crew chief who operated David Pearson's Racing School for many years.
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