A lug wrench, also colloquially known as a

tire iron A tire iron (also tire lever or tire spoon) is a specialized metal or plastic tool used in working with tires. Tire irons have not been in common use for automobile tires since the shift to the use of tubeless tires in the late 1950s. Bicycl ...

, is the name for a type of

socket wrench A socket wrench (or socket spanner) is a type of spanner (or wrench in North American English) that uses a closed ''socket'' format, rather than a typical open wrench/spanner to turn a fastener, typically in the form of a nut or bolt. The most ...

used to loosen and tighten

lug nut A lug nut or wheel nut is a fastener, specifically a nut (hardware), nut, used to secure a wheel on a vehicle. Typically, lug nuts are found on automobiles, trucks (lorries), and other large vehicles using rubber tires. Design A lug nut is a ...

s on

automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...

wheel A wheel is a rotating component (typically circular in shape) that is intended to turn on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machin ...

s. In the United Kingdom and Australia, it is commonly known as a wheel brace.

Forms

Lug wrenches may be L-shaped, or X-shaped. The form commonly found in car trunks is an L-shaped metal rod with a

on the bent end and a prying tip on the other end. 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 called a spider wrench, is made in the shape of a cross with different sized sockets on each of the four ends. Other names are ''four way wheel wrench'', ''spanner'', ''brace'', or ''cross''.

Technique

Ideally, the nuts (or bolts) should be tightened with a

torque wrench A torque wrench is a tool used to apply a specific torque to a fastener such as a nut, bolt, or lag screw. It is usually in the form of a socket wrench with an indicating scale, or an internal mechanism which will indicate (as by 'clicking', ...

. 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 A brake is a machine, mechanical device that inhibits motion by absorbing energy from a moving system. It is used for Acceleration, slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of ...

rotor ROTOR was an elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers. To get it operational as quickly as possible, it was initially made up primarily of WWII-era syst ...

if the car is equipped with

disc brakes Disc or disk may refer to: * Disk (mathematics), a two dimensional shape, the interior of a circle * Disk storage * Optical disc * Floppy disk Music * Disc (band), an American experimental music band * ''Disk'' (album), a 1995 EP by Moby Other ...

. For this reason,

impact wrench An impact wrench (also known as an impactor, impact gun, air wrench, air gun, rattle gun, torque gun, windy gun) is a socket wrench power tool designed to deliver high torque output with minimal exertion by the user, by storing energy in a ro ...

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 centered and restrained by ''all'' nuts (as often the first nut 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 In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). The symbol for torque is typically \boldsymbol\tau, the lowercase Greek letter ''tau''. Wh ...

(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. This tool also has a secondary usage: it can be used to remove vehicles that are stuck in the snow by breaking up ice so it can be easily shovelled away from the drive wheels.

References

External links

Appropriate Tightening Sequence
Bolt-Science's example and explanation of using a criss-cross tightening sequence. {{Hand tools Tires Wrenches