What Causes Lug Nuts To Keep Coming Loose?by Casey Holmes
Keeping your tires on the road is the cornerstone to keeping you safe when you're driving. The lug nuts that secure the tires to your vehicle need to be checked routinely for signs of loosening to ensure safety. There are a variety of different reasons why your lug nuts may end up loose, and knowing what they are can help keep you and your passengers safe on the road.
Most wheels today are made of an aluminum alloy and are held to the hub with steel lug nuts. These two different metals expand and contract at different temperatures which can cause them to loosen as they heat up and cool down. This can cause lug nuts to loosen even if they are torqued to factory standards. It's a common occurrence after wheels have been removed and reinstalled. This can be caused by the temperature at application in contrast to the temperature outdoors. If the shop where the tires are installed is too hot or cold compared to the ambient temperature outdoors, it can lead to contraction or expansion.
Over or Under Torquing
Under torquing your tires is a simple explanation for loose lug nuts. If they are improperly tightened, then your tire security will be at a minimum. However, you may not realize that over torquing may also be just as bad in terms of securing your lug nuts. Over torquing reduces clamping force by stretching the studs or threads beyond the ability to be responsive. This is especially true when it's done repeatedly. Over torquing can also lead to other problems such as cracked, seized, or cross threaded nuts that cannot apply the same clamping force.
Improper Mating Surfaces
Improper mating surfaces can cause poor clamping force as well, including damaged and contaminated areas. Contaminants can include excess dirt, sand, rust, metal burrs or paint. Proper clamping force cannot be achieved with non-flat mating surfaces such as damaged or bent hubs. Clamping force can also be diminished with worn out or elongated bolt holes. When contaminants are present, they can also change the torque relationship and cause false torque. This is where torque applied to overcome friction is not converted into clamping force.
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