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RESOURCES IN TECHNOLOGY Figure 3. The Chrysler Crossfire is a high performance sports vehicle that emphasizes luxurious styling, speed, handling, and cornering capabilities. This product was designed and tested for speeds up to 150mph. The tire and wheel assemblies include forged alloy rims and ZR-rated tires. Additionally, this vehicle features different sized tires on the front and rear of the vehicle to improve handing and cornering with P225/40ZR18 on the front and P255/35ZR19 on the rear. The temperature ratings range from A, B, or C. They again are measured indoors in a controlled environment on a simulated road wheel test stand. The ratings are gauged on 30-minute successive runs. The temperature indication ratings measure the tire speed where heat from friction would cause the tire to fail. “A” ratings withstand the temperature generated on the wheel machine at 114mph. B ratings are gauged at 99mph, while C ratings are gauged at 85mph (www.1010tires.com/tiretech.asp). Other sidewall markings include season ratings (MS for all seasons, AT for all terrain, and M+S for mud and snow), tire manufacturing date, manufacturing site, and tire inflation pressures. NHTSA reported that the Firestone Wilderness ATX tires, the ones that led to consumer lawsuits of Ford Explorer and Firestone in 2001, were rated as B for traction and C for temperature (www.dot.gov/affairs/ nhtsa5101.htm). So, although price is important to consumers, understanding the numbers on the sides of tires might lead to longer-life tires and improved driving safety. Wheel and Tire Care There are many products on the market advertised to clean wheels. Besides road grime, brake dust also accumulates on the wheels. When you purchase specialty wheels, learn the metal (alloys) from which they are manufactured. When you purchase your wheel cleaning detergents they need to be appropriate for the metal used to manufacture the wheel. Usually the car washing soap you are using to wash your car will not cut the brake dust. Do not use extra strong household cleaners if the wheel manufacturer recommends against this. It could mar the finish of your wheels. Also, clean one wheel at a time, since the sun can dry cleaners and make them hard to remove. Car wax can be applied to nontextured wheels and it will assist in the cleaning process. Specialty sprays can be purchased from automotive stores that will also repel brake dust and road grime. Tires should be visually inspected to insure a safe ride. Some learn to look at their tires each time they enter their car. Others do this at regular maintenance intervals. Visual inspections can show excessive wear, puncture materials that may have lodged themselves in your tires, or low air pressures. Catching problems early can extend the life of tires and prevent flats from puncturing objects. Maintaining proper air pressure in tires is important for proper wear. A recent NHTSA survey found that about 30% of cars and light trucks have at least one tire under inflated by 8psi or more. (www.nhtsa.gov/cars/testing/utqg/) Tires do lose pressure over time from the changes in heat, both from driving and the atmosphere. Improper inflation of tires can cause excessive and irregular wear, poor vehicle handling, and decreased gas mileage. Improper tire pressures can result in tire failure. Visual inspection can usually identify problems. A quality air gauge should be used to check correct tire pressures. Tires should be checked when they are cold, since driving warms the tires and increases their pressure. The optimum pressures are located on the sidewall of the tires and also in the owner’s manual. Some newer models of automobiles have electronic sensors and circuitry, which display lights on the instrumentation if tire pressure is low. Also remember to check the pressure of your spare tire. Nothing is more irritating than having a flat tire and then finding the spare is also flat. Balancing of tires is undertaken when they are installed. They can come out of balance because of wear or in the original manufacturing process (tires can be heavier where the circular tread is cohered to complete the circle). Tires may be balanced on or off a vehicle. Two types of balancing are static and dynamic. Dynamic balancing is accomplished by spinning the wheel assembly on a balancing machine at highway speeds and then adding the necessary wheel weights to counteract any imbalance. Typically, out-of-balance wheels will “bounce” or “wobble.” A balancing machine marks the spot in the circular tire where it is the heaviest. The balancing weights are put on the opposite side from where the tire/ wheel is the heaviest. When you replace tires, this is when balancing usually occurs. Visual inspection should note if the weights used for balancing fall off and need to be replaced. If the tires do not have unusual wear or create vibrations felt in the steering wheel, they probably do not need rebalanced during tire rotations. Since tires wear differently in the front and rear due to weight 20 April 2005 • THE TECHNOLOGY TEACHER
RESOURCES IN TECHNOLOGY distribution, turning, and traction, they should be rotated at regular intervals. A good way to build this into your maintenance schedule is to have the tires rotated at every other oil change (6000 to 7500 miles). When you have a new set of tires installed on your vehicle, wheel alignment should be checked. The vehicle is aligned at manufacture, but it can get out of alignment (wheels running parallel to each other) by the wheels hitting other cars, curbing, or deep holes. When the wheels are out of alignment they cause unusual tread wear and handling and can damage the suspension of the vehicle. So to increase the life of your tires, it is important to get the alignment corrected if you notice unusual tire wear or driving handling. Using a proper maintenance schedule, tires can last for the mileage at which they are rated. It is not uncommon to get 50,000 miles on a set of tires that are rated for this mileage by keeping the tires properly inflated and rotated on a schedule. Government Involvement in the Tire Industry Safety ratings are important to consumers. As with all technology, consumers cannot be knowledgeable on all topics. Technology education is the school subject that should provide much of this knowledge and a consumer attitude that you can learn about new technologies by conducting consumer research. Governments assist citizens in many technical areas. Tire technology is one such area. Because of potential injury to consumers and others, the U.S. government established the National Highway Traffic Safety Administration and its Uniform Tire Quality Grading (UTQG) rating system. It is involved in the rating of new tires and also follows up if drivers are reporting incidents with current tires and other vehicle system failures. It is important that there are “watchdog” government groups, because the proper research may not go into the post-manufacturing performance of consumer products. Many tires and other consumer products are being manufactured in other countries. What are the driving conditions and automotive requirements in these countries? How do they align with what is needed in your country? Today many tire manufacturers are partnering with Chinese companies because of lower material and labor costs. Chinese companies are also trying to produce their own lines of internationally accepted tires. They may succeed. However, as increasing automotive products enter the market, countries and/or companies may not be responsible for the performance quality of their manufactured products. This is why we need the government involved— consumer protection. Government is also involved in the proper disposal of tires. Because of their composition, it is hard to recycle tires. Many have been dumped and catch on fire. This causes toxic fumes and carbon black smoke. Disposal fees are imposed by the government and passed onto consumers by the tire retailers. These fees are used to aid in research to find better ways to dispose of the tires. Learning Lab Activity Research and discussion of wheels, tires, and their maintenance can be a valuable learning experience. Following are some viable technology literacy activities. 1. Have students bring in the sidewall information from their primary vehicle’s tires. Determine speed, load, tread wear, traction, and temperature ratings. Discuss if any students were surprised with the tire performance indicators as compared to the car/truck model. Write vehicle models and tire markings on the board for comparisons. 2. Shop online for tire pricing ads. Remember to look into the overall tire ratings and compare prices. Students might have to visit the Web pages of the tire manufacturers to check on details of the tire performance criteria. 3. Have students research wheel cleaners by visiting automotive departments and stores. Discuss the cleaner information they found. 4. Use Car Builder or Truck Builder computer software programs to design a car or truck. Explore how changing wheel and tire sizes can increase or decrease vehicle performance, such as speed, handling, and ride comfort. Summary Automotive wheels and tires require knowledge to understand their specifications and use. While the durability and useful life of tires have increased substantially over the last several decades, in all probability you will purchase a number of vehicle tires over your lifetime. Knowing how they are made and what the numbers mean will assist you in making informed and intelligent consumer purchasing decisions. Basic tire maintenance such as tire air pressure, balancing, and rotation can extend the useful life of tires and maintain their safety, performance, and handling features. References 10 10 Tires.Com (2004). Tire & wheel tech. Retrieved December 20, 2004, from www1010tires.com/tiretech.asp Tyson, R. (October 2001). NHTSA announces initial decision that additional Firestone wilderness AT tires have a safety defect; Firestone agrees to recall those tires, NHTSA 51-01. Retrieved January 6, 2005, from www.dot.gov/affairs/nhtsa5101.htm Wikipedia. (2004). Tire. Retrived December 20, 2004, from http://en.wilipedia.org.wiki/Tire National Highway Traffic Safety Administration. (2004). Tire ratings database lookup results. Retrieved January 9, 2005 from www.nhtsa.dot.gov/cars/testing/UTQG/ pages/TireRatings.cfm National Highway Traffic Safety Administration. (2004). Tire safety. Retrieved January 14, 2005 from www.nhtsa.gov/cars/testing/utqg/ John M. Ritz, DTE is professor and chair at Old Dominion University, Norfolk, VA. He can be reached via e-mail at jritz@odu.edu. THE TECHNOLOGY TEACHER • April 2005 21
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