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# Importance of reading tires is not over-inflated

5/15/2008

If you have ever seen a Sprint Cup prerace practice you may have seen the Goodyear engineers taking tire temperatures on the race cars as soon as they come off the track. They are recording vital information for the teams on how their car is performing with the setup they have chosen to run at that particular track.

The tires will tell you a lot about what is going on with your race car. If you have the car set up properly then the temperature readings taken across the tires will be even or close to even. If they are not even [or uniform] then they can tell you what you need to do to help get them even.

The goal in setting up a race car is to get all four tires working equally in achieving grip so you maximize the amount of tire patch that is contacting the race track surface at all times. If you don't and your competitor does then his chances of winning the race are better than yours because he can drive through the corners at a higher speed.

When the Goodyear engineers take the temperatures of the tires they take three readings per tire. One reading is taken about an inch off of the inside edge of the tire surface, one in the middle and one about an inch off the outside edge of the tire tread. Those three readings on the right and left front tires will tell the teams if they have the proper suspension [primarily camber] settings and that the tires are properly inflated.

If, for example, the inside reading of a right front tire is hotter than the center or outside reading then it tells the crew chief that he has too much camber in that wheel. If it is too hot on the outside reading then he does not have enough camber. If both the inside and outside readings are hotter than the center then the tire is under inflated. Conversely, if the center of the tire is hotter than the outside readings then it is probably over inflated. Again, the goal is to have all three readings be the same or as close to each other as possible.

The ideally balanced race car would have all 12 temperature readings [four tires times three readings each] be equal. However, that is very difficult to achieve so the teams work to get them as close to each other as possible.

The teams and Goodyear use an instrument called a pyrometer to measure the temperatures. Some pyrometers have a needlelike probe that is inserted into the surface of the tire while others are infrared and can take the tire temperature simply by holding them about three inches from the tire's surface. I have used both and the infrared pyrometer is much quicker to use and is therefore more accurate because you want to record all 12 of the readings as quickly as possible because the tires will cool down rapidly.

If both the front tire temperatures are fairly equal but are higher than the combined rear tire temperatures then that tells the crew chief the car is pushing going into the corner. If the rear tire temperatures are greater than the front tire temperatures then it tells the crew chief that the car is loose. This is important information to the crew chief because a driver will sometimes "think" a car is loose when it is really pushing and he is snapping it loose by the way he is driving it without realizing he is doing it. The tire temperatures tell the true tale of what is going on so that is what the crew chief relies on to confirm that the information he is receiving from his driver is correct.

Sometimes a car can be "throttle loose," which means the driver is breaking the rear end free by applying too much power too quickly coming out of the corner. This will primarily occur on a short track such as Martinsville where the speed differentials in a lap can be much greater. The crew chief can read the tire temperatures to determine if that is what is happening versus the car having been set up loose. If it is the former then the crew chief can drop a very large hammer on the driver's right foot and cure the problem. If it is the latter then he will have to make adjustments to the car instead.

The crew chief lives and dies by his notes from tests, previous practices and races at a particular race track so he has a good idea what type of setup he needs to achieve the best performance, which would be reflected in the tire temperature readings. The driver also has a definite impact on how a car performs as well. Remember, setting up a race car is done through the correct usage of basic geometry and physics calculations.

The one variable or unknown element in the equation is the driver. This is where communication plays a vital role between the crew chief and driver. What the driver perceives to be "loose" may not be what the crew chief would perceive to be "loose" so the tire temperatures educate the crew chief to help him better understand what his driver means when he says the car is doing something he does not like. The driver may believe that A + B = C while the crew chief may believe that A + B = D, but as long as he understands what "C" is through interpretation of his tire temperature readings then he can adjust accordingly and the driver will be happy.

Some drivers can give a crew chief accurate and helpful information based on their prior experience while other drivers don't have the required knowledge to give the crew chief good feedback on what the car is doing. So the tire temperature readings become the interpreter between the driver and crew chief on what the car is really doing on the track.

One old crew chief I knew many years ago used to say "Drivers lie but race cars don't." What he meant was drivers could not be relied upon to provide accurate information while an instrument such as a pyrometer is always consistent and reliable in experienced hands. A driver once told me the race car "feels all squiggly." OK, just let me look up "squiggly" in my notes and we'll fix it. "Squiggly?"

Race car tires have an extremely thin tread thickness on them to help dissipate unwanted heat because they do not have a tread pattern on them like your street tire. The total tire surface of a NASCAR race tire is in contact with the track surface, giving it a bigger tire patch and greater grip but also building up more heat. Excessive heat can blister a tire and render it useless.

Race tires have rows of small indentations [wear bars] across the tread width at equally spaced intervals around the circumference of the tire. These "dimples" allow the engineers to check or "read" the wear across the solid surface of the tire. This is another method of confirming the car's setup is correct.

If the outside area of the tire tread is wearing away more rapidly than the inside then the crew chief should be able to make an adjustment to the car's setup to compensate for it or the driver could possibly alter his line to reduce or minimize the uneven wear. Reading the tires after each pit stop can give the crew chief constant feedback throughout the race and influence what adjustments he makes to the car during the next pit stop.

You have probably seen tire engineers or tire specialists heating the surface of a race tire with a small torch and then scraping across the tire's surface with a putty knife shortly after the tire came off the car during a race. They are removing the used rubber from the tire so they can check the wear bars built into the tread to confirm that the car is doing what they want it to do.

One of the many calculations that the Goodyear engineers take into consideration is how many laps a car can run on a full tank of fuel. Most teams will change tires when they pit for fuel, so a tire that can maintain a decent grip a little longer than the cars can race on a tank of gas allows Goodyear to give the teams a tire that provides optimum grip while remaining safe and reliable for them to race on. The average life of a street car tire is about three years while the average life of a race tire is measured in minutes.

While Goodyear fills the tires they mount at the track with dry air, most of the teams will purge that air from their tires and replace it with nitrogen. Regular compressed air can contain moisture and other impurities that can increase the pressure of the tire when it gets heated by friction during the race. Nitrogen is a dry gas so it will remain more stable than regular air and therefore maintain a more uniform tire pressure.

NASCAR's current rules require that the teams deliver their rims to Goodyear and have that week's tires mounted at the track when they arrive. They also must return their used and unused tires to Goodyear before they leave the track. All of the mounting and return of the tires is supervised by a NASCAR official. Goodyear provides the teams a special grooved tire [for easy identification] that is used while the cars are moved around when the actual racing tires are not available to them.

So if a team has missed the mark on their setup when they arrive at the track, they can use their practice time to dial it in by reading and interpreting the information that the race car and driver are giving them.

The crew chief can check his tachometer readings to make sure he has the correct gearing to keep his selected engine in the proper power band for that track. He can check his shocks to make sure the car has the proper suspension travel and he most definitely will check his tire temperature readings each and every time the car goes out to practice.

In racing, the tires tell the tale on how well a team and driver are doing and what they need to do to improve their performance.

Bill Borden is a former championship winning crew chief who operated David Pearson's Racing School for many years.