View source for Lug nut

{{short description|Fastener, specifically a nut, used to secure a wheel on a vehicle}}
{{Other uses|Lugnut (disambiguation)}}
{{use mdy dates|date=November 2015}}
[[File:Wheel Nuts All Details.png|thumb|300px|From left: 9 lug nuts and 4 lug nut attached to screw-in [[wheel stud]]s.]]
[[Image:lug-nuts.jpg|right|thumb|300px|A [[bolt circle]] with four lug nuts on an [[Acura]].]]

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 [[automobile]]s, [[truck]]s (lorries), and other large vehicles using rubber [[tire]]s.

==Design==
A lug nut is a [[nut (hardware)|nut]] fastener with one rounded or conical (tapered) end, used on steel and most aluminum [[wheel]]s. A set of lug nuts is typically used to secure a wheel to threaded [[wheel stud]]s and thereby to a vehicle's [[axles]]. Some designs (Audi, BMW, Mercedes-Benz, Saab, Volkswagen) use lug [[Screw|bolts]] or wheel bolts instead of nuts, which screw into a tapped (threaded) hole in the wheel's hub or brake [[drum brake|drum]] or brake [[Disc brake|disc]].

The conical lug's taper is normally 60 degrees (although 45 degrees is common for wheels designed for racing applications), and is designed to help center the wheel accurately on the axle, and to reduce the tendency for the nut to loosen due to [[Precession (mechanical)|fretting induced precession]], as the car is driven. One popular alternative to the conical lug seating design is the rounded, hemispherical, or ball seat. Automotive manufacturers such as [[Audi]], [[BMW]], and [[Honda]] use this design rather than a tapered seat, but the nut performs the same function.{{dubious|date=September 2014}}{{Citation needed|date=September 2014}} Older style [[alloy wheel|(non-ferrous) alloy wheel]]s use nuts with a {{cvt|1/2|to|1|in|mm|order=flip}} cylindrical shank slipping into the wheel to center it and a washer that applies pressure to clamp the wheel to the axle.

Wheel lug nuts may have different shapes. Aftermarket alloy and forged wheels often require specific lug nuts to match their mounting holes, so it is often necessary to get a new set of lug nuts when the wheels are changed.

There are four common lug nut types:

# cone seat
# bulge cone seat
# under hub cap
# spline drive.

The lug nut [[Screw thread|thread type]] varies between car brands and models. Examples of commonly used [[ISO metric screw thread|metric threads]] include:<ref name="boltsirkel.no">[http://www.boltsirkel.no/ Boltsirkel.no]</ref><ref name="floorjackshop"/>

* M10×1.25&nbsp;mm
* M12 (1.25, '''1.5''' or 1.75&nbsp;mm [[thread pitch]], with M12x1.5&nbsp;mm being the most common<ref>[https://cartreatments.com/lug-nut-sizes-types/ Lug Nut Sizes (w/ Chart For All Car Manufacturers through 2020)]</ref>)
* M14 (1.25, '''1.5''' or 2&nbsp;mm pitch, with M14×1.5&nbsp;mm being the most common{{citation needed|date=September 2020}})
* M16×1.5&nbsp;mm

Some older American cars use inch threads, for example {{frac|7|16}}″-20 (11.1&nbsp;mm), {{frac|1|2}}″-20 (12.7&nbsp;mm), or {{frac|9|16}}″-20 (14.3&nbsp;mm).<ref name="floorjackshop">[https://www.floorjackshop.com/lug-nut-sizes/ Lug Nut Sizes for All Car Manufacturers (with Chart)]</ref>

<gallery widths="200px" heights="155px">
Andreas Mikkelsen's Car at Service in Gap (4), Rallye Monte-Carlo 2019.jpg|Car with [[wheel stud]]s for use with lug nuts
TSM350 - 2015 - Stierch 19.jpg|Five yellow lug nuts for use on a car with [[wheel stud]]s
Give me a... yeah, alright. (15694589508).jpg|Car without wheels studs for use with lug bolts
Kugelbundschrauben-92154.jpg|Four lug bolts, from left: Three M12×1.5&nbsp;mm bolts with different length and one M14×1.5&nbsp;mm bolt
</gallery>

==Removal and installation==
[[Image:Callipers Twin Pot.jpg|thumb|Disc brake with five wheel studs sticking out]]

Lug nuts may be removed using a [[lug wrench|lug]], [[socket wrench|socket]], or [[impact wrench]].  If the wheel is to be removed, an automotive [[Jack (device)|jack]] to raise the vehicle and some [[wheel chock]]s would be used as well.  Wheels that have [[hubcap]]s or wheel covers need these removed beforehand, typically with a [[screwdriver]],<ref>{{cite web
| publisher = NSX Prime
| url =http://www.nsxprime.com/FAQ/DIY/remove_wheels/removing_the_wheels.htm
 | title = Removing and Installing Wheels
| year = 1997
 |access-date = October 4, 2007
 }}</ref> 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.<ref>{{cite web| first = Matthew | last = Wright | publisher = About.com | url = http://autorepair.about.com/od/quicktips/ss/lugtight_order.htm | title = What Order Do I Tighten My Lug Nuts? | access-date  = April 22, 2010}}</ref> 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.

The tool size needed for removal and installation depends on the type of lug nut. The three most common hex sizes for lug nuts are 17&nbsp;mm, 19&nbsp;mm, and 21&nbsp;mm, while 22&nbsp;mm, 23&nbsp;mm, {{frac|11|16}} inch (17.5&nbsp;mm), and {{frac|13|16}} inch (20.6&nbsp;mm) are less commonly used.

==Detecting loose nuts==
In order to allow early detection of loose lug nuts, some large vehicles are fitted with [[loose wheel nut indicator]]s.  The indicator spins with the nut so that loosening can be detected with a visual inspection.

==Anti-theft nuts or bolts==
{{Multiple image | width=140 | image1=Kugelbund-Felgenschloss und Felgenschloss-Adapter-92162.jpg | image2=Kugelbund-Felgenschloss und Felgenschloss-Adapter-92163.jpg | footer=Spherical wheel lock bolt and associated key, the latter with stepped 17&nbsp;mm and 19&nbsp;mm AF hex drive}}

In countries where the theft of [[alloy wheel]]s is a serious problem, locking nuts (or bolts, as applicable) are available — or already fitted by the vehicle manufacturer — which require a special adaptor ("key") between the nut and the wrench to fit and remove.  The key is normally unique to each set of nuts.  Only one locking nut per wheel is normally used, so they are sold in sets of four.  Most designs can be defeated using a hardened removal tool which uses a left-hand self-cutting thread to grip the locking nut, although more advanced designs have a spinning outer ring to frustrate such techniques. An older technique for removal was to simply hammer a slightly smaller socket over the locking wheel nut to be able to remove it. However, with the newer design of locking wheel nuts this is no longer possible. Removal nowadays requires special equipment that is not available to the general public. This helps to prevent thieves from obtaining the tools to be able to remove the lock nuts themselves.{{dubious|date=September 2023}}

==History==

In the United States, vehicles manufactured prior to 1975 by the Chrysler Corporation used [[Screw_thread#Handedness|left-hand and right-hand screw thread]] for different sides of the vehicle to prevent loosening.  Most Buicks, Pontiacs, and Oldsmobiles used both left-handed and right-handed lug nuts prior to model year 1965.<ref>{{cite web 
| first = Steve
| last = Magnante
| work = Car Craft Magazine
| url =http://www.hotrod.com/articles/ccrp-0607-junkyard-crawl-lefthand-lugs/
| title = Junkyard Crawl—Left Hand Lug Nuts Not Just for Mopars
| date = Nov 6, 2006
| access-date = December 8, 2016
 }}</ref>  It was later realized that the taper seat performed the same function.  Most modern vehicles use right-hand threads on all wheels.

== See also ==
* [[Center cap]]
* [[Wheel sizing]]

==References==
{{reflist}}

== External links ==
* {{commonscatinline|Lug nuts}}
* {{commonscatinline|Wheel locks}}

{{Nuts (hardware)}}

{{DEFAULTSORT:Lug Nut}}
[[Category:Nuts (hardware)]]
[[Category:Vehicle parts]]