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COVER Michigan State Police Tire Tests 1 2 1. The Firestone Firehawk GT Pursuit generally came in first or second place in performance on the three vehicles it was tested. 2. The Goodyear Eagle RS-A generally came in second or third place in performance on the five vehicles it was tested. 3. The Nokian WR G2 turned in a solid second place performance, often ending up between the Firestone and Goodyear. in a turn on wet asphalt. The tires were tested in both new condition and in half-worn condi- tion. Half-worn, in this case, means after being driven 100 laps around a one-mile road course simulating pursuit or emergency driving con- ditions. All vehicle tests were also conducted with the original equip- ment (OE) tires for comparison purposes. A Ford CVPI with new tires was used as a "control vehicle" for the purpose of monitoring any changes in the test surfaces over the course of the two-week testing program. 3 The dry asphalt stopping distance testing evaluates the com- patibility of various replacement tires offered for police service with each vehicle's brake and chassis control systems. Likewise, the wet Jennite stopping distance tests simulate the compatibil- ity of the replacement tires in lower coefficient road conditions. The braking-in-a-turn (BIT) testing on wet asphalt provides the basis for evaluating the compatibility of the various replacement tires with the vehicle chassis control systems including anti-lock brake system (ABS) and stability control. Finally, the steady-state, static circle, turning test addresses the ultimate, lateral traction and stability of the vehicles fitted with the various replacement tires. This same set of four test- ing protocols was also conducted on the tires after 100 laps of simulated pursuit or emergency driving to evaluate these same tires in a worn condition. This testing protocol permits comparative assessments of var- ious replacement tires offered for police service in each vehicle configuration evaluated, and also permits similar assessments of these same tires in a new versus worn condition. Therefore, relevant comparisons of performance between tires offered for the same vehicle will be addressed. In addition, comparisons of performance of the same tire in a new versus worn condition were compiled to assess the significance of this aspect of tire performance. Measurements of tire wear at each vehicle wheel position were also quantified. Although not specifically relevant to 'nor- mal' tire-wear life estimates, a directly comparable measure of tire wear by tire position and vehicle model was compiled from the testing program results. Results, Not Recommendations The MSP does not make recommendations, or even offer an as- sessment of the results for any of the tire, brake pad or patrol vehicle testing they do in conjunction with the NIJ. Instead, they publish all of the results of all their testing in exhaustive detail. It is up to the individual police and sheriff's departments across the U.S. and Canada to review the results, make an evaluation as it pertains to their unique needs, and then make decisions based on that agency-specific evaluation. The tires from Cooper, for example, were run on three differ- ent police sedans – and they were disqualified in each case. They simply could not complete the test sequence. They wore past the trend blocks on the Impala and wore all the way into the cords on the Charger and CVPI. The Cooper tires may be available in a size that fits the police vehicle, but it failed the tests that more police-oriented tires easily passed. Two very different tires from Pirelli performed quite well. The Pirelli P6 Four Seasons beat the Goodyear tire in every new tire test category (dry, wet, wear) on the Impala. In the half-worn condition, the Pirelli continued to either beat or tie with the Goodyear. It makes you wonder about the decision by GM to switch from the Pirelli P6 Four Seasons to the Goodyear Eagle RS-A on their police package Impala. The other Pirelli tire, the PZero Nero, did well on the Ford CVPI. It performed midway between the Firestone and the Goodyear in nearly every test phase. On the other hand, the PZero Nero is a much more expensive tire than the comparable police tires from Firestone and Goodyear, and arguably less available. 24 LAW and ORDER I May 2012