Lug nut
Encyclopedia
A lug nut is a fastener
, specifically a nut
, used to secure a wheel
on a vehicle
. Typically, lug nuts are found on automobile
s, truck
s (lorries), and other large vehicles utilizing rubber tire
s.
with one rounded or conical (tapered) end, used on steel and most aluminum wheels. A set of lug nuts are typically used to secure a wheel
to threaded wheel stud
s and thereby to a vehicle's axles.
Some designs use lug bolts
instead of nuts, which screw into a tapped (threaded) hole in the wheel's hub or brake drum
or disc
. This configuration is commonly known as a bolted joint.
The lug's taper is normally 60 degrees (although 45 is common for wheels designed for racing applications), and is designed to center the wheel accurately on the axle, and to reduce the tendency for the nut to loosen, due to fretting induced precession
, as the car is driven. Honda
uses a spherical rather than a tapered seat, but the nut performs the same function. Older style alloy wheel
s have a 1/2 to 1 inch shank slipping into the wheel to center it and a washer that applies pressure to clamp the wheel to the axle.
Lug nuts may be removed using a lug
, socket
or impact wrench
. If the wheel is to be removed then an automotive jack to raise the vehicle and some wheel chocks would be used as well. Wheels that have hubcap
s or hub covers need these removed beforehand, typically with a screwdriver
, flatbar, or prybar. Lug nuts can be difficult to remove, as they may become frozen to the wheel stud. In such cases a breaker bar
or repeated blows from an impact wrench can be used to free them. Alternating between tightening and loosening can free especially stubborn lug nuts.
Lug nuts must be installed in an alternating pattern, commonly referred to as a star pattern. This ensures a uniform distribution of load across the wheel mounting surface. When installing lug nuts, it is recommended to tighten them with a calibrated torque wrench
. While a lug, socket or impact wrench may be used to tighten lug nuts the final tightening should be performed by a torque wrench, ensuring an accurate and adequate load is applied. Torque
specifications vary by vehicle and wheel type. Both vehicle and wheel manufacturers provide recommended torque values which should be consulted when an installation is done. Failure to abide by the recommended torque value can result in damage to the wheel and brake rotor/drum. Additionally, under tightened lug nuts may come loose with time.
s, which spin with the nut and highlight misaligned nuts.
Fastener
A fastener is a hardware device that mechanically joins or affixes two or more objects together.Fasteners can also be used to close a container such as a bag, a box, or an envelope; or they may involve keeping together the sides of an opening of flexible material, attaching a lid to a container,...
, specifically a nut
Nut (hardware)
A nut is a type of hardware fastener with a threaded hole. Nuts are almost always used opposite a mating bolt to fasten a stack of parts together. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts...
, used to secure a 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,...
on a vehicle
Vehicle
A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....
. Typically, lug nuts are found 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...
s, truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...
s (lorries), and other large vehicles utilizing rubber tire
Tire
A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...
s.
Design
A lug nut is a nutNut (hardware)
A nut is a type of hardware fastener with a threaded hole. Nuts are almost always used opposite a mating bolt to fasten a stack of parts together. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts...
with one rounded or conical (tapered) end, used on steel and most aluminum wheels. A set of lug nuts are typically used to secure a 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,...
to threaded wheel stud
Wheel stud
Wheel studs are the threaded fasteners that hold on the wheels of many automobiles. They are semi-permanently mounted directly to the vehicle hub, usually through the brake drum or brake disk. Lug nuts are fastened over to the wheel stud to secure the wheel...
s and thereby to a vehicle's axles.
Some designs use lug bolts
Screw
A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...
instead of nuts, which screw into a tapped (threaded) hole in the wheel's hub or brake drum
Drum brake
A drum brake is a brake in which the friction is caused by a set of shoes or pads that press against a rotating drum-shaped part called a brake drum....
or disc
Disc brake
The disc brake or disk brake is a device for slowing or stopping the rotation of a wheel while it is in motion.A brake disc is usually made of cast iron, but may in some cases be made of composites such as reinforced carbon–carbon or ceramic matrix composites. This is connected to the wheel and/or...
. This configuration is commonly known as a bolted joint.
The lug's taper is normally 60 degrees (although 45 is common for wheels designed for racing applications), and is designed to center the wheel accurately on the axle, and to reduce the tendency for the nut to loosen, due to fretting induced precession
Precession (mechanical)
Precession is the process of a round part in a round hole rotating with respect to that hole because of clearance between them and a radial force on the part that changes direction. The direction of rotation of the inner part is opposite to the direction of rotation of the radial force. Fretting...
, as the car is driven. Honda
Honda
is a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...
uses a spherical rather than a tapered seat, but the nut performs the same function. Older style alloy wheel
Alloy wheel
Alloy wheels are automobile wheels which are made from an alloy of aluminium or magnesium. They are typically lighter for the same strength...
s have a 1/2 to 1 inch shank slipping into the wheel to center it and a washer that applies pressure to clamp the wheel to the axle.
Removal and installation
Lug wrench
Lug wrench is the U.S. name for a type of socket wrench used to turn lug nuts on automobile wheels. In the UK it is commonly known as a wheel brace or wheel wrench....
, socket
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,...
or 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...
. If the wheel is to be removed then an automotive jack to raise the vehicle and some wheel chocks would be used as well. Wheels that have hubcap
Hubcap
A hubcap, wheel cover or wheel trim is a decorative disk on an automobile wheel that covers at least a central portion of the wheel. Cars with stamped steel wheels often use a full wheel cover that conceals the entire wheel. Cars with alloy wheels or styled steel wheels generally use smaller...
s or hub covers need these removed beforehand, typically with a screwdriver
Screwdriver
A screwdriver is a tool for driving screws and often rotating other machine elements with the mating drive system. The screwdriver is made up of a head or tip, which engages with a screw, a mechanism to apply torque by rotating the tip, and some way to position and support the screwdriver...
, flatbar, or prybar. Lug nuts can be difficult to remove, as they may become frozen to the wheel stud. In such cases a breaker bar
Breaker bar
A breaker bar is a long non-ratcheting bar that is used with socket wrench style sockets. Breaker bars are used to 'break loose' very tight fasteners because their additional length allows the same amount of force to generate significantly more torque than a standard length socket wrench. The use...
or repeated blows from an impact wrench can be used to free them. Alternating between tightening and loosening can free especially stubborn lug nuts.
Lug nuts must be installed in an alternating pattern, commonly referred to as a star pattern. This ensures a uniform distribution of load across the wheel mounting surface. When installing lug nuts, it is recommended to tighten them with a calibrated 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...
. While a lug, socket or impact wrench may be used to tighten lug nuts the final tightening should be performed by a torque wrench, ensuring an accurate and adequate load is applied. 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....
specifications vary by vehicle and wheel type. Both vehicle and wheel manufacturers provide recommended torque values which should be consulted when an installation is done. Failure to abide by the recommended torque value can result in damage to the wheel and brake rotor/drum. Additionally, under tightened lug nuts may come loose with time.
History
Some cars made up to about 1960 used left-hand and right-hand threaded lug nuts for different sides of the vehicle to prevent loosening, until it was realized that the taper seat performed the same function. In order to allow the easy detection of loose lug nuts, some large vehicles are fitted with loose wheel nut indicatorLoose wheel nut indicator
Loose wheel nut indicators are small pointed tags, usually made of fluorescent yellow plastic, which are fixed to the lug nuts of the wheels of large vehicles. The tag rotates with the nut, and if the nut becomes loose, the point of the tag shifts noticeably out of alignment with the other tags...
s, which spin with the nut and highlight misaligned nuts.