Flat, Ball, and Acorn Lug Nuts: Seating Styles Explained

Reviewed by

Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Written by CarParts.com Research Team - Updated on September 3rd, 2024

Reading Time: 4 minutes
Summary
  • The seat is the part of the lug nut that sits flush against the wheel surface. Different wheels have varying lug nut hole sizes and shapes. If the lug nuts are of the correct seating style, each lug nut will sit properly flush against the side of their hole.
  • If the lug nut’s seating style doesn’t suit the hole exactly, the lug nuts will damage your wheels and axles.
  • The types of lug nut seating styles include acorn lug nuts, ball lug nuts, and extended thread lug nuts. Most lug nut seating styles also come in long, short, closed, or open types, depending on the lug nut’s cap.

What you might not know is that there are different types of lug nuts on the market, and each of these types is designed to suit a specific application. In this article, we’ll be taking a look at the different kinds of lug nuts out there and why you should make sure you’re using the right ones on your wheels.

How Important Are Lug Nut Seating Styles?

The seat is the part of the lug nut that sits flush against the wheel surface. It slots inside the lug nut hole, which varies in size and shape. The different lug nut seating styles are designed to fit into these holes accordingly. The correct style will fit into the corresponding hole in such a way that the lug nut sits flush against the sides of the hole. Some lug nuts aren’t tapered, but have big washers attached.

If the lug nut’s seating style doesn’t suit the hole exactly, the lug nuts will damage your wheels and axles, stripping the wheel and leaving the lug nut holes unusable. The wheels will also grow unstable and loose. Always buy lug nuts with the correct seating style for your wheels.

In this illustration, one type of standard OEM aluminum wheel lug nut is pictured, and one type of lug nut for steel wheels. Using the wrong lug nuts can and will cause a wheel to come off. Some have 60 degree tapers, some 90 degrees. Some lug nuts have “ball” shaped tapers and some have flanges, so be careful that you’re using the right nuts for your application. | Image Source: Richard McCuistian

Lug Nut Seating Styles

There are four main types of lug nut seating styles. We’ll go into them in detail in this section. Remember that these lug nut types only cover seating styles. Most lug nut seating styles also come in long, short, closed, or open types, depending on the lug nut’s cap.

Acorn Lug Nuts

Acorn lug nuts, which are also known as conical seat lug nuts or tapered lug nuts, are the most common seating style. They’re easy to work with because they can self-center when tightened. One end of an acorn lug nut is tapered like a cone to account for the taper on the wheel’s lug nut seat. Acorn-style lug nuts are available with 60- or 45-degree tapers. The 60-degree acorn lug nut seating style is more common than the 45-degree one.

Most aftermarket wheels use the 60-degree acorn lug nut, while Circle Track and NASCAR race wheels typically require 45-degree acorn lug nuts. In addition, 45-degree acorn lug nuts tend to have larger, wider surfaces to engage the wheel more securely.

Ball Lug Nuts

Ball lug nuts have a rounded or spherical end. They look similar to acorn lug nuts when installed, but they lack the cone shape of true conical lug nuts. They aren’t as common as acorn lug nuts, but they serve similar purposes.

Extended Thread Lug Nuts

Extended thread lug nuts, also known as ET lugs, have a conical seat similar to acorn lug nuts. They also have an extra shank, which gives them more thread engagement. In other words, extended thread lug nuts seat deeper into the wheel’s lug nut holes than other lug nut types.

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Mag Lug Nuts

Mag lug nuts also have an extended thread design, but what makes them special is the flat washer that usually accompanies each lug nut. This washer allows them to sit flush against the flat surface around the lug nut hole. They’re not as common these days, having been popular back when aluminum tires were originally released.

Flat Lug Nuts

Flat lug nuts are similar to mag lug nuts in that they sit flush against the flat surface surrounding a specific type of lug hole. However, these lug nuts have built-in washers and lack the extended thread design of mag seat lug nuts. It’s more difficult to torque flat lug nuts down compared to mag lug nuts, but they’re definitely more convenient to use. You’ll commonly find that semi-truck wheels and other industrial vehicles need this type of lug nut seating style.

As you’ve learned, there are a whole host of different lug nut seating styles out on the market. Choosing from these types of lug nuts can be a bit daunting, which is why it’s best to consult a professional if you aren’t sure what type your wheels need. After all, the last thing you want is to get them wrong and ruin your wheels in the process.

Reviewed By Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com 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 CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

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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Published by
CarParts.com Research Team and Richard McCuistian, ASE Certified Master Automobile Technician
Tags: lug-nut