Lug wrench
Encyclopedia
Lug wrench is the U.S. name for a type of socket wrench
Socket wrench
A socket wrench is a wrench with interchangeable heads called sockets that attach to a fitting on the wrench, allowing it to turn different sized bolts and other fasteners. The most common form is a hand tool popularly called a ratchet consisting of a handle with a ratcheting mechanism built in,...
used to turn lug nut
Lug nut
A lug nut is a fastener, specifically a nut, used to secure a wheel on a vehicle. Typically, lug nuts are found on automobiles, trucks , and other large vehicles utilizing rubber tires.-Design:...
s on automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...
s. In the UK it is commonly known as a wheel brace or wheel wrench.
Socket wrench
A socket wrench is a wrench with interchangeable heads called sockets that attach to a fitting on the wrench, allowing it to turn different sized bolts and other fasteners. The most common form is a hand tool popularly called a ratchet consisting of a handle with a ratcheting mechanism built in,...
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 (sometimes known as a spider) is made in the shape of a cross, with different sized sockets on each of the four ends.
Ideally, the nuts (or bolts) should be tightened with a torque wrench
Torque wrench
A torque wrench is a tool used to precisely apply a specific torque to a fastener such as a nut or bolt. It is usually in the form of a socket wrench with special internal mechanisms. It was invented by Conrad Bahr in 1918 while working for the New York City Water Department...
. Lug wrenches are much less expensive because they lack the ability to measure or limit the force used. Installing a wheel 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
Brake
A brake is a mechanical device which inhibits motion. Its opposite component is a clutch. The rest of this article is dedicated to various types of vehicular brakes....
rotor if the car is equipped with disc brakes. For this reason, impact wrench
Impact wrench
An impact wrench is a socket wrench power tool designed to deliver high torque output with minimal exertion by the user, by storing energy in a rotating mass, then delivering it suddenly to the output shaft.Compressed air is the most common power source, although electric or hydraulic...
es should properly be used only for removing lug nuts, not for tightening them, although in practice this rule is often ignored for convenience's sake, even by professional mechanics.
When re-fitting a wheel, the nuts (or bolts) should be tightened in a criss-cross pattern (to even out the forces) and initially should only be tightened 'finger tight' on all nuts. In this context 'finger tight' is tight enough to reach the point where free play is taken up and proper tightening is about to begin, say, the tightening force using the lug wrench/wheel brace like a screwdriver. This should be repeated twice, to ensure the wheel is properly centred and restrained by all nuts (as often the first nut(s) that is tightened will be slightly loose after completing the set for the first time), then the wheel should be lowered to the ground and the criss-cross tightening pattern repeated to modest torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
(say few fingers force on the lug wrench/wheel brace arm), and then finally repeated to full hand force.
Rarely, and more often with large trucks and lorries, 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 finally tighten the wheel lug nuts to the proper torque specification as soon as possible after using a lug wrench to affix a wheel. At the very least, the lug nuts should be checked for tightness after 50–100 km/miles when things have been subject to some vibration and thermal cycling.
Lug wrenches are known for their use as weapons in cases such as road rage
Road rage
Road rage is an aggressive or angry behavior by a driver of an automobile or other motor vehicle. Such behavior might include rude gestures, verbal insults, deliberately driving in an unsafe or threatening manner, or making threats. Road rage can lead to altercations, assaults, and collisions...
, as they are readily available in most cars, made of metal and heavy enough to cause injury.
Lug wrenches are occasionally mistaken for tire iron
Tire iron
A tire iron is a specialized metal tool used in working with tires that have inner tubes.Tire irons have not been in common use for automobile tires since the shift to the use of tubeless tires in the late 1950s...
s, due to the relative rarity of the tire iron, another metal tool of similar size which is not often needed by those who do not work with cars.
External links
- Wheel Nut Wrenches Commercial site of tool manufacturer (shows several types of wheel/lug wrench).
- Appropriate Tightening Sequence Bolt-Science's example and explanation of using a criss-cross tightening sequence.