Findings and methodology are reported for the evaluation of the pursuit-rated winter performance of the following police vehicle tires: Nokian WRG3, Goodyear Ultra GRIP, Firestone Firehawk, and Firestone Firehawk PVS.
In order to be eligible for testing, a tire had to hold a W speed rating (capable of speeds from 150 to 168 mph); must come in all sizes required by the Michigan State Police patrol fleet; and must be rated as a snow or all-season tire. The Firestone Firehawk was found to be a V -rated tire, but it was still tested, since it appeared to have an aggressive tread pattern. Since the rear-wheel drive of the Dodge Charger was experiencing the most complaints from officers, this vehicle was used as the testing platform. It is capable of 152 mph, requiring a W speed-rated tire. The tires were tested in P225/60R18 size on the rear-wheel Dodge Charger and in P245/55R18 size on the all-wheel drive Dodge Charger. Given the number of complaints on tire traction from the northern most posts of the Michigan State Police, the testing directive required testing the tires in the winter conditions of the Upper Peninsula of Michigan. Arrangements were made to use the Keweenaw Research Center in Hancock, MI. January 2015 was the test date. The tests developed were acceleration, braking, steady state turn, and hill start. The conditions and requirements for each test are described. Figures present test results.