Wheel studs are the

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s that hold on the

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s of many

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s. They are semi-permanently mounted directly to the vehicle hub, usually through the

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

brake disk A disc brake is a type of brake that uses the calipers to squeeze pairs of pads against a disc or a "rotor" to create friction. This action slows the rotation of a shaft, such as a vehicle axle, either to reduce its rotational speed or to hold ...

Lug nut A lug nut or wheel nut is a fastener, specifically a 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 nut fastener wi ...

s are fastened onto the wheel stud to secure the wheel. When a wheel is removed for tire changes etc., the stud remains in the hub. Many automobiles instead use bolts to do this, where removable bolts screw into the wheel hub. Wheel studs can be either factory equipment or aftermarket add-ons.

Benefits of studs vs. bolts

The primary advantage of wheel studs over wheel bolts is greater ease for tire changes by creating the ability to lift both the wheel and tire onto the studs creating the ability to hold and locate the assembly during tire changes rather than trying to hold up the wheel and tire while lining up the holes to insert a bolt. Many wheels that use bolts also have one or more small locator pins to assist this: the wheel is lifted onto the pins, then the bolts inserted. Once the bolts are tightened and the wheel is fully installed, the pins have no further function whilst the vehicle is being driven. Another advantage of using wheel studs is that they are replacable and usually require fewer parts for replacement in case of stripped threads. With lug bolts, on the other hand, the whole hub usually has to be replaced in case of stripped threads in the hub. One motivation for using lug bolts instead of wheel studs and nuts the number of parts that needs to be attached to the wheel hub. Wheel studs and lug nuts consist of two parts, while the lug bolt is a single part. This leads to one less part when using lug bolts, which can save manufacturing costs. Andreas Mikkelsen's Car at Service in Gap (4), Rallye Monte-Carlo 2019.jpg, Car with wheel studs for use with lug nuts TSM350 - 2015 - Stierch 19.jpg, Five yellow lug nuts for use on a car with wheel studs Give me a... yeah, alright. (15694589508).jpg, Car without wheel studs for use with lug bolts Kugelbundschrauben-92154.jpg, Four lug bolts, from left: Three M12x1.5 mm bolts with different length and one M14x1.5 mm bolt

Types

Wheel studs are replaceable and come in two basic kinds: press-in and screw-in. Welded-in studs are possible but unlikely to be encountered.

Screw-in

Screw-in studs simply screw into the existing threaded bolt hole in the hub. The end that screws into the hub is usually either threaded with a smaller tolerance (tighter fit) or installed with a chemical

thread-locking fluid Thread-locking fluid or threadlocker is a single-component adhesive, applied to the threads of fasteners such as screws and bolts to prevent loosening, leakage, and corrosion. Most thread-locking formulas are methacrylate-based and rely on t ...

to keep it from backing out from the hub when the lug nut is removed.

Press-in

Press-in studs are installed from the back side of the disk or drum hub and may require removal of the hub from the vehicle for installation or removal. They consist of a threaded portion and a larger diameter section, called the knurl, that is splined to prevent rotation. The diameter of the knurl is larger than the hole in the hub requiring a press fit to seat the stud. The stud is prevented from being pulled through the hub by a larger diameter stop on the end. Most press-in studs are designed and recommended to be installed with a mechanical or

hydraulic press A hydraulic press is a machine press using a hydraulic cylinder to generate a compressive force. It uses the hydraulic equivalent of a mechanical lever, and was also known as a Bramah press after the inventor, Joseph Bramah, of England. He inven ...

to ensure proper seating without damage. It is possible, though not advised, to install a press-in by using a

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and

nut Nut often refers to: * Nut (fruit), fruit composed of a hard shell and a seed, or a collective noun for dry and edible fruits or seeds * Nut (hardware), fastener used with a bolt Nut or Nuts may also refer to: Arts, entertainment, and media Co ...

to "draw" it into the hub. In doing so, the installer must ensure that the stud is fully seated and that no damage is done to the threaded portion of the stud. While a common installation method by many garage mechanics, this method puts excessive strain on the stud, and can cause it to stretch and fatigue, which could lead to premature failure.

Aftermarket wheel studs

Aftermarket wheel studs offer the ability to mount a wheel that is not factory supplied to that vehicle. Screw-in studs with a larger than original threaded diameter portion permit mounting of wheels with larger diameter holes. Wheel studs of longer length allow the use of wheel spacers to move a wheel further out to compensate for rubbing or backspacing issues, to make the wheel look like it is larger than factory standard, or to increase the track width of the car.

References

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