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Fan appreciation night at Clinton County Speedway Roger and Trish Eriksen Next Friday, July 30, will be Fan Appreciation Night at the Clinton County Speedway, Kentucky’s super track. The price of admission has been cut significantly for that night. Bring your spouse or your favorite friend and enjoy a night of professional stockcar racing for less than the price of admission to a movie theatre. If you’re a regular spectator at the super track, now would be a great time to ask your neighbors to come along. Call a friend. Tell them the good news. If you’ve never been to the super track, now would be the perfect opportunity to enjoy professional racing at its finest. There will be a full program of Open Wheel cars, Road Hogs, and Chevettes. Plan on attending for a complete night of qualifying, trophy dashes, heat races, and feature races. You will watch some of the best stockcar drivers in the country compete at one of the smoothest and best maintained dirt tracks in the country. Be there! Stockcar drivers utilize a variety of chassis and engine components to cause their stockcars to race around the track in as short a time frame as possible. Some of these components include well-known items such as springs, shock absorbers and carburetors, and, some lesser-known items such as birdcages, torque arms and stud girdles. However, none of the chassis components used and none of the engine components used affect the handling performance of a stockcar as much as the tires. The tires are the single most important component in any racecar. The best set up racecar with the most powerful engine available will go nowhere if it has inappropriate tires for the racetrack. Rubber tires have two very important physical properties rolled into one complex material. First, rubber tires are elastic. They can be compressed when a force is applied and the energy of compression is stored in the rubber. When the force is withdrawn, the tire returns to its original shape and the stored energy is released. This elastic property of tires can be likened to a spring. A spring can be repeatedly compressed and extended but will return to its original shape when all forces acting on it are withdrawn. Because a spring releases almost 100 percent of the energy of compression or extension back to the source when that force is withdrawn, a spring does not heat up very much during use. Similarly, a tire generates very little heat as a result of its elastic property. The second important property of tires is their viscosity. Viscosity is the property of a fluid that resists a force causing it to flow. While we ordinarily don’t think of a tire as a fluid, tires do have a viscous component. This component can be likened to a shock absorber. It takes energy to compress or extend a shock absorber, but that energy is not given back in the same way that a spring does. Most of the energy liberated by a shock absorber is in the form of heat. (After a feature race a crewmember can readily touch a spring, but must be careful with the shocks; they may be hot.) It is the viscous component in a tire that causes it to heat up. For example, take a dry, flat kitchen sponge and push down on it while sliding it across a counter top. Notice that it is easy to push and as soon as you let go of it the sponge returns to its original shape. Now soak the sponge in a viscous fluid (water) and repeat the above. Notice that it is more difficult to push the sponge and when you let go of it the sponge takes its sweet time returning to its original shape. The energy to return to its original shape is provided by the sponge’s elastic property and the viscous fluid must return through all of the small holes and chambers within the sponge. While it’s hardly measurable, there is a small amount of heat liberated in the fluid within the sponge. A tire made of a soft compound will heat up more readily than a tire made from a hard compound. A softer tire will absorb more energy because the forces of acceleration, deceleration, and sliding cause the tire tread to deflect more than a hard tire. However, as a tire heats up the elastic energy increases exponentially, therefore, the stored energy increases with each revolution of the tire. But, the viscosity decreases with the increase in temperature. This effect can be likened to oil that pours easier after it is hot. Tests have shown that as a tire heats up, more heat energy is stored by the tire’s elastic property and less energy is liberated as heat by its viscous property. Therefore, each tire of a given compound will reach a defined limit of operating temperature when combined with given air temperature, track moisture content, and racing conditions. In other words, the tire temperature is self-limiting. A tire will heat up to a certain temperature and then stay there for the duration of the race. However, any change in air temperature, track moisture content, or racing conditions will cause an almost immediate change in tire temperature. As a tire heats up, its tread gets softer and will adhere (stick) to the racetrack better than when cold. However, if a tire heats up beyond its normal operating temperature the tread will “give out,” that is, the tire will no longer “stick” to the track surface. When a tire “gives out,” it does so almost immediately after reaching its critical temperature. During the running of the Battle of the Bluegrass Late Models last June 11, Michael Luna was racing a strong se cond behind leader Tyrel Todd with only four laps to go. Suddenly, one or more of Michael’s tires “gave out,” and within only three laps Michael went from 2nd place to 5th place. Fortunately for Michael, the race ended when it did. The 6th place car was on his bumper. In this instance, the track surface continued to dry during the race and the heat continued to build in one or more of Michael’s tires. If the track had not dried out, Michael’s tire(s) probably would have lasted the entire race. The length of the race then is of lesser importance than is the air temperature or track moisture conditions when a race crew decides which tire compound to use for a race. The two exceptions to this degree of importance occurs during qualifying or trophy dashes when there is not sufficient time for the tire to heat up, and, when the race is long enough that tire wear becomes an issue. The next time you are in the grandstand cheering for your favorite driver and he/she suddenly goes from the front of the pack to near the back, you can assume that a tire “gave out.” Yes, there are other reasons for this to occur, but in most cases overheated tires are the culprits. Trying to out guess the weather and track moisture conditions is difficult. Sometimes even the most experienced race crew will get it wrong. As a race fan, all you can do is repeat the words of Chicago Bear fans, “Wait till next week.” There’s only one speedway with a track of smooth clay, (both tires and shocks run cooler on a smooth track), you ain’t seen nothin’ till you’ve been to Clinton County Speedway! As a reminder, on Friday, July 30, will be Fan Appreciation Night at the super track. The price of admission to the grandstand for that night has been reduced so low you will not have to borrow from your piggy bank. There will be a full program of Open Wheel cars, Road Hogs, and Chevettes. Be there! Actors dislike playing Hamlet to an empty theatre, ball players dislike hitting home runs into an empty bleacher, and racecar drivers dislike winning when the grandstand is not full. So please wear your seat belt. We need you! Sources • Furney, C.P. Jr., P.E. Selection & Application of Late-Model Dirt Racing Tires. Tennessee Valley Publishing, 2001 • Bolles, Bob. Stock Car Setup Secrets. The Berkley Publishing Group, New York, 2003 • Smith, Steve. Stock Car Dirt Track Technology. Steve Smith Publications, California, 1995 Add a comment |
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