Most experts agree, however, that changing the make or style of tires can impact negatively on vehicle performance; it is more advisable to replace tires with the exact stock factory tires. Not only will better performance be assured, but, by replacing a tire with original equipment, agencies will avoid potential liability problems. Often police departments buy different makes of replacement tires because of budgetary concerns, new safety standards, a local tire lobby, or a willingness to trade off some other area of performance against the tires. Following a General Accounting Office report in the 1960's indicating that tires are generally purchased on a low bid which may lead to serious safety and wear problems, most State and municipal agencies are now required to purchase only tires on the Qualified Products List. This article describes recommended tires produced by major manufacturers including Bridgestone, Cooper, Dunlop, Firestone, General, Goodyear, Hercules, Pirelli-Armstrong, and Uniroyal-Goodrich.