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  • Lug nuts are metal fasteners that attach the wheel to the vehicle and keep it in place.
  • Swollen lug nuts appear scuffed, rusty, or warped.
  • The common reasons for swollen lug nuts are rust, galvanic corrosion, and applying excessive force with bad impact sockets.
  • Swollen lug nuts can prevent you from removing a flat tire.

A lug nut is a metal fastener that secures and positions a wheel on a vehicle. It can become swollen over time due to moisture and corrosion. Swollen lug nuts can become difficult to remove using standard tools. You might not be able to change a flat tire if you have a swollen lug nut, and that’s a situation you don’t ever want to find yourself in.

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Find out about the dangers of swollen lug nuts and why you should replace them as soon as possible.

What Does a Swollen Lug Nut Look Like?

Two-piece lug nuts are nice and shiny because they’re made from two kinds of metal. Steel is used to make the lug nut. Then a chrome sheet metal covering is added to make it shine. Rust can form in between the two layers of dissimilar metals over time, causing them to expand and warp.

The lug nut on the left is an example of a normal lug nut, while the one on the right is an example of a swollen lug nut. Swollen lug nuts tend to look rusty, warped, or scuffed from being taken on and off.

normal and swollen lug nu
Swollen lug nuts tend to look rusty, warped, or scuffed from being taken on and off.

What Causes Lug Nuts to Swell?

Steel can corrode and push against the nut’s chrome cover, causing it to enlarge. This can happen naturally through galvanic corrosion. When two dissimilar metals are exposed to one common electrolyte, one of the metals can corrode. Force can also accelerate the swelling of a lug nut. Removing lug nuts with cheap impact sockets can cause the top chrome layer to loosen and create an opening for water, salt, and corrosion. This problem is prevalent in some Jeep, Toyota, Ford, Chrysler, and Dodge models.

Are Swollen Lug Nuts Dangerous?

As an example, a twenty-one-millimeter lug nut can grow to twenty-two millimeters when it swells. This becomes a problem when you have to change tires on the fly and your lug wrench doesn’t fit around the nut anymore. Severe corrosion can cause the chrome cover to fall off and expose the steel nut underneath. You can end up stranded on the side of the road if you can’t remove the lug nuts to change a flat tire.

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removing lug nuts
A swollen lug nut becomes a problem when you have to change tires on the fly and your lug wrench doesn’t fit around the nut anymore.

How to Remove Swollen Lug Nuts

A standard lug wrench might not be enough to remove a swollen lug nut. To avoid damaging the wheel, we recommend asking your mechanic to remove the lug nut for you. They have the tools and know-how to extract this part safely.

When to Replace Lug Nuts

Lug nuts are designed to last the life of the vehicle, but they can fail prematurely due to rust and swelling. You’ll want to replace swollen or damaged lug nuts as soon as possible.

About The Authors
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Contact Center Manager and Technical Reviewer at

William “Bill” Guzenski has produced hundreds of how-to videos for the automotive community. He’s an ASE Certified Master Automobile Technician, and is affiliated with the Specialty Equipment Market Association (SEMA). He loves attending race events and car shows throughout the country, as well as traveling in his 40-foot motorhome, exploring abandoned mines and ghost towns.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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