A common site in your neighborhood auto garage is a mechanic tightening up the lug nuts on your car with an impact wrench. You hear the common screech of the impact wrench as it makes quick work of the lug nuts. You also probably rarely see that same mechanic actually use a torque wrench. Impact wrenches are great tools but they can and will over tighten the lug nuts on your car. At first that doesn’t sound like a bad thing. Tight is good, right? Not necessarily.
Most manufacturers recommend using a torque wrench when tightening lug nuts. They will specify a certain ft/lb to dial in on the torque wrench. This insures the nuts are tightened properly. Over tightening can damage the studs and possibly lead to a failure in the future. Here is what happens. When the nuts are tightened, the studs will stretch. This tension holds the wheels on to the rim. If you over tighten the studs you can damage them and they could fail.
The best approach is to use your impact wrench to snug up the nuts. Then go back with a torque wrench and tighten to the manufacturer specifications. Next time you are having your tires rotated or changed, make sure the mechanic uses a torque wrench and the correct torque. Having the proper tools makes all the difference and will extend the life of your car.