Even if you don't have any intention of doing work on your vehicle yourself, it is still important to know how to use a torque wrench. If you ever have to change a flat tire yourself, you'll be especially thankful that you know how to properly use the tool.
Torque is a rotation force applied around a point, and the amount of force you need to apply depends on the length of the torque wrench. The main difference between a torque wrench and a regular one is that the former can be set to let you know when you've reached the optimal tightness. One end of the tool will have a dial where you can set the pressure level that you want to achieve. Some wrenches may provide measurements in both imperial and metric units, so it is important to make sure you're adjusting the wrench for the correct measurement.
Once you've set the wrench to the proper settings, it's time to use the wrench. Gradually turning the wrench will be easier than trying to apply too much pressure all at once. Plus, it will allow you more control so you don't accidentally over-tighten the bolt. When it gets harder to turn the wrench, you are getting close to the optimal tightness, and once this has been reached, the torque wrench will make a cracking noise and give way a bit. Stop tightening the bolt when this happens.
When it comes to changing a tire, the amount of force you will need to tighten the lug nuts depends on the type of vehicle you drive, and this information can be found in the owner's manual. Getting this measurement right is especially important, because over-tightening the lug nuts on a wheel can damage the thread on the bolts and make it difficult to remove them. Leaving them too loose can cause of the wheel coming clean off of the vehicle, which will drastically increase the risk of a crash.
When removing or tightening lug nuts and any bolts that are placed in a circular pattern, you should always tighten then in a criss-crossing pattern. In most cases, the owner's manual will provide a sequence for you to follow.