Lug wrench

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A lug wrench is the USA name for a type of socket wrench used to turn lug nuts on an automobile wheel. In the UK they are commonly known as a Wheel Wrench (used to turn wheel nuts/bolts).

The form commonly found in car trunks is an L-shaped metal rod with a socket wrench on the bent end and a prying tip on the other. The prying tip is mainly intended to remove hub caps or wheel covers that may be covering a wheel's lug nuts. Another common type is made in the shape of a cross, with different sized sockets on each of the four ends.

Ideally, a mounted tire should be installed with a torque wrench. Lug wrenches are much less expensive because they lack the ability to measure or limit the force used. Installing a tire with a lug wrench thus requires a bit of rough guessing about proper tightness. Excessive force can strip threads or make the nuts very difficult to remove. Also, uneven torque between the various lug nuts, or excessive torque, can lead to warping of the brake rotor if the car is equipped with disc brakes. Rarely, insufficient force can lead to the nuts coming undone while in use. Because of this, it is best to use a torque wrench or similar tool to tighten the wheel lug nuts to the proper torque specification as soon as possible after using a lug wrench to affix a wheel.

Lug wrenches are known for their use as weapons in cases such as road rage, as they are readily available in most cars, made of metal and heavy enough to cause injury. They are also increasingly referred to as tire irons, due to the relative rarity of the tire iron, another metal tool of similar size which is not needed on modern tubeless automobile tires and so has not been in common use for several decades.