When you buy new tires and wheels, lug nuts are probably the last thing you think about. Honestly, they aren’t very exciting. You know what is exciting though? Having one of your wheels pass you as you drive down the road! Lug nuts and the corresponding lug studs are the critical link between your vehicle and those big, heavy tires and wheels that we love so much.
The basic factors related to wheel fasteners are:
• Thread diameter
• Thread pitch
• Thread length/thread engagement
• Seat type
• Proper torque
Increasing the number of lug studs generally requires an axle swap, but installing larger studs is one way to increase the clamping force and strength of the connection between your axles and your wheels. Additionally, having the right lug nuts for your wheels is absolutely critical. Most (but not all) aftermarket wheels use a conical seat, but many factory wheels (such as those found on Ford Super Duty) use a flat seat. When switching from an OEM wheel to an aftermarket wheel, always purchase the lug nuts that match your new wheel type. Otherwise you might be in for more excitement than you want.
Typically, you want the thread engagement of a lug nut to be at least equal to the diameter of the stud. So if you have a 1/2-inch stud, you want at least half an inch of thread engagement. This is one situation, though, where more is better.
The “seat” refers to the shape at the base of the lug nut where it contacts the wheel. The most common seats for aftermarket wheels are conical, although there are some radius seats. Flat seats are common on factory wheel offerings and can sometimes be found on aftermarket wheels as well. The reason conical seats are the most common is because they are less dependent on hub register and lug stud size, allowing one wheel to fit a larger number of applications.
Lug studs and the corresponding nuts can be found in SAE and metric sizing, with metric gaining in popularity and not just limited to foreign brands. In SAE sizing, a 1/2x20 size has a 1/2-inch diameter and 20 threaders per inch. In metric sizing, a 14x1.5 has a 14mm diameter with 1.5mm between the threads. So a larger number for thread pitch means a finer thread with SAE sizing but a courser thread pitch for metric sizing.
We are guilty of using an impact gun on our wheels. We always turn the gun down though and just run the lug nuts on until they’re barely tight, then we perform the final tightening with a torque wrench. Proper torque is a function of the lug size, as shown in the chart.
Splined lugs are popular with the tuner crowd, and they are showing up on more truck wheels as well. Many new wheel styles have small opening for the lug holes. This is done for aesthetic reasons, but it makes it difficult to fit a normal lug nut and socket on the wheel.
The wheel must be centered to the axle hub in order to run true. This can be done via the lugs or the hub. If the wheel registers via the center bore, it is considered “hubcentric.” Hubcentric wheels are more common in OEM wheels than aftermarket wheels designed to fit a variety of applications. Lugcentric wheels, where the studs are used to center the wheel, are far more common in the aftermarket. With lugcentric wheels, the size of the lug holes in the wheel should closely match the lug size on the vehicle to ensure the best fit.
Lug nuts with a tapered or stepped sizing allow you to run a smaller socket. This is beneficial because you can run a thicker socket (such as an impact socket) before concerns about the socket fitting inside the lug opening of the wheel.
We prefer to run lug nuts that are open on the top, allowing us to see exactly how far the studs are engaged. While you might not consider these as visually appealing, they make it easy to perform a quick visual inspection and see if anything is amiss.