The Michigan State Police's precision driving unit has released the results of an intensive battery of tests measuring the ability of aftermarket tires to meet the often-punishing demands of law enforcement driving.
Troopers in the unit tested six tire brands -- Cooper, Firestone, Goodyear, Nitto, Nokian and Pirelli -- on various law enforcement vehicles to rate the durability of aftermarket tires for agencies. During two weeks of testing in June, tires were studied in three major areas: braking, endurance and steady-state turning.
In addition to the four individual tests, troopers also measured tire wear after two 50-lap runs. Tires were run counterclockwise for 50 laps and clockwise for another 50 laps. The percentage of wear for each tire was then then measured.
The police tested the following tires:
* Goodyear Eagle RS-A on the Dodge Charger, Ford Crown Victoria Police Interceptor (CVPI), Chevrolet Caprice, Chevrolet Impala and Chevrolet Tahoe;
* Firestone Firehawk GT Pursuit on the Charger, CVPI and Tahoe;
* Cooper CS4 on the CVPI, Impala and Charger;
* Nokian WR G2 on the Caprice and Impala;
* Nitto NT 850 Plus on the Caprice, Impala and CVPI; and
* Pirelli P Zero Nero on the CVPI and Pirelli P6 tire on the Impala.
Tire evaluators purchased the tires from a retail store to ensure each tire was an actual production version.
The results? On the Caprice, Nitto performed best in the wet and dry test, while Nokian performed best in the braking and turning test.
On the Charger, the Cooper performed best in all three tests combined, but was too worn to be tested in the "worn" tests. Goodyear came out on top in the dry test, while Firestone was first in the wet test. When braking during a turn for the worn tires, Goodyear came in first.
On the Tahoe, Firestone performed better in three out of the four "new tire" tests, but was too worn to be tested against the Goodyear tire in the "worn" tests.
On the Impala, Cooper had the best performance in the four "new tire" tests. On the CVPI, Cooper performed best in two of the four tests but came in fourth in the braking-during-a-turn test, and third in the lateral acceleration test, while Nitto performed best in three of the four "worn" tire tests.
To read more about the tests, check "Michigan State Police evaluate aftermarket tires" on www.policemag.com. The Police magazine blog by Paul Clinton and Greg Basich also contains a link to the complete 352-page report.
Police is a sister publication of Modern Tire Dealer.
