If you’re planning on putting new(er) aluminum or other modern wheels on an older vehicle, especially from the early 70s or older — wheel stud length can be an issue.
What Is Wheel Stud Thread Engagement?
These older cars usually have shorter wheel studs because they only came with thin steel wheels.
The thickness of a wheel can differ from original equipment wheels to aftermarket wheels. For that reason, it’s critical to verify that the wheel nuts or lug nuts will properly engage the threads.
The rule of thumb for lug nut thread engagement of a wheel stud into the lug nut must be equal to at least the diameter of the stud.
For example, a 7/16-20 stud would need 7/16 in. engagement, or about 9 full turns of the lug nut; a 1/2-20 stud would need 1/2 in. engagement, or 10 full turns of a lug nut, and so on. See the table below for all sizes.
Lug nuts, lug bolts, and wheel locks should always be tightened to the recommended torque specifications found in your vehicle’s owner’s manual.
Refer to the chart below to determine the number of turns, or the depth of engagement, typical for your stud or bolt size.
| Bolt/Stud Thread Size | Minimum Number of Turns |
|---|---|
| M14x2.0 | 7 |
| M14x1.5 | 9.5 |
| M14x1.25 | 11 |
| M12x1.75 | 7 |
| M12x1.5 | 8 |
| M12x1.25 | 9.5 |
| 1/2″-20 | 10 |
| 5/16″-18 | 6 |
| 7/16″-20 | 8.5 |
| 9/16″-18 | 10 |
Even with ET Style lug nuts, be sure to check for sufficient thread engagement.
What Are ET Style Lug Nuts?
“ET” = Extended (or Extra) Threads
If your wheel studs are too short, pressing longer studs in is always an option. But, an easier solution for wheels with conical seats would be to use ET Style lug nuts.
These lug nuts have the same 60° conical seat plus a small 0.300″ long shank that will fit into most aftermarket wheels. This equates to about 6 additional full turns of thread engagement, which will usually allow for the safe installation of the wheels.
ET lug Nut Use With Wheel Adapters and Spacers
ET lug nuts can also be instrumental in a wheel adapter installation for the same reason mention above; older vehicles generally have shorter studs.
To make up for the thickness of the adapter or spacer, ET lug nuts with a 0.300″ extended shank, good for roughly 6 turns of engagement.
Shop Wheel Adapters and Spacers
Extended Thread ET Lug Nut Sets
Safe and proper installation requires using the correct tools and procedures. This will prevent over-tightening the wheel fasteners, stripping the fastener threads, and stretching the studs.
