Foot-pounds

Foot-pounds is a unit of torque, meaning it measures rotational force rather than straight-line weight or pressure. It answers the question of how hard a fastener is being twisted, which matters because both too little and too much torque can cause problems. A bolt tightened too loosely can work its way free, while one tightened too much can stretch, strip, or snap.

Lug nuts are the most common place a home mechanic runs into a foot-pound spec, since automakers publish an exact torque value for wheel fasteners and overtightening them by hand or with an impact wrench can warp brake rotors or make lug nuts difficult to remove later. Many other fasteners on a vehicle, from oil drain plugs to suspension bolts, have their own published torque specs as well.

A torque wrench is the tool that lets you hit a specific foot-pound number instead of guessing by feel, and it is worth checking a wrench's calibration periodically since repeated use and drops can throw off its accuracy. A common mistake is using an impact wrench for final tightening on critical fasteners instead of finishing the last stage with a calibrated torque wrench.