We have all seen our local mechanic tightening lugnuts with a pnumatic wrench. You hear the screech of the impact wrench as it tightens the lug nuts quickly. You will probably rarely see a mechanic actually use a torque wrench. Torque wrenches are good tools but they can and will over tighten the lug nuts of your auto. So why is that a bad thing? Its good to make them ti? Not necessarily. Many manufacturers recommend using a torque wrench when tightening lug nuts. The manufactureres specify a certain ft/lb  on the torque wrench. This insures the nuts are tightened to just the right amount. if you tighten a lug nut too much you can damage the studs which leads to a failure in the future. When you tighten the nuts, the studs stretch. This is what holds the wheels on to the rim. If you over tighten the studs you can damage them. When you have your tires rotated or changed, make sure the mechanic uses a torque wrench and the correct settings.