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UP CLOSE Tire Basics - Tire Forensics ARTICLE SUMMARY The tire inflation that prevents sudden fail- ures. The tire repairs that maintain speed ratings. Why nitrogen protects the TPMS. What valve stem caps really do. The miss- ing step in tire mounting. The secrets to long tire life and better gas mileage. The "Rick and T.J. Show" has it all. MORE INFORMATION www.goodyear.com www.bfusa.com S Goodyear's Rick Wendt points out the width of the inner belts. The patch/plug combo must engage these belts. Under inflation is the leading cause of tire failures. By Police Fleet Manager Staff O ne of the most popular sessions of any Police Fleet Expo is the Tire Basics – Tire Forensics presenta- tion. The class is taught by the tag team of Goodyear's Rick Wendt, backed up by engineering support from Joe Dancy, and Firestone's T.J. Tennent. Tis PFE session is not a simplistic, "how-to read tire sizes" and "this is what aspect ratio means" kind of presentation. Instead, it is a hard and focused look at police pursuit tires in actual police use: how to get the best tire wear; how to get the best fuel economy; how to prevent a "blow-out." Leading Cause of Failure Te single most important aspect of tire use and 46 Police Fleet Manager Jul-Aug 2012 maintenance is also the simplest: proper infla- tion pressure. For almost all police and special- service package vehicles, that means 35 psi, cold. And "cold" means first thing in the morning, or not driven for the past two hours, or driven for less than 2 miles. Heat builds up while the tire is being driven. Tis heat raises the air pressure inside the tire. For example, 35 psi (cold) may be 40 psi (hot). Check the tire pressure cold. Proper tire pressure is so important that it is the very first diagnostic step when any tire concern whatsoever is raised. Under inflation reduces the load carrying capacity of the tire. Tink 450 pounds of cargo in the trunk of your Ford CVPI and tires inflated to only 30 psi, which is just 15 percent under inflated. Under inflation increases the sidewall flex as the vehicle is being driven. Tat causes exces- sive internal heat build-up. Heat is the number one enemy of any tire. Under inflation also in- creases the rolling resistance of the tire, which greatly reduces fuel economy. Under inflated tires greatly affect the handling and driving dynamics of the tire. Tat also means braking ability. Under inflated tires produce longer stopping distance in emergency situations. You reduce fuel economy by 33 percent running on 20 percent under inflated tires. You reduce tread life by 50 percent by running on 20 percent under inflated tire. Tires lose 1 psi of pressure every month. Tires lose 1 psi of pressure for every 10 deg F drop in ambient temperature. Today's 17- and 18-inch police tires have such low profile sidewalls, not even a tire expert can tell if they are under inflated just by looking at them. You must use a tire gauge. Rotate tires every 3,000 miles. When you change the engine oil, check the tire pressure. When you check the oil level, check the tire pressure. Regardless, check the tire pressure at least once a month.