Wheel Nut Thread Size & Thread Pitch
The thread size and thread pitch of a lug nut, lug bolt, or wheel lock will determine whether or not the lug will screw on to your wheel stud. You can identify your thread size and pitch with a thread pitch gauge available at any hardware or auto parts store. You can also take one of your lugs to your local hardware or auto parts store and spin it onto the bolts they have on hand.
What is Thread Size?
The thread size is the measurement taken across the outside diameter of your wheel stud threads measured in either standard (1/2", 9/16", etc.) or metric (M12, M14, etc.) dimensions. The most common thread sizes are 10mm, 12mm, 14mm, 7/16", 1/2", 9/16", 5/8". You can usually find your factory stud size in your vehicle owner's manual.
What is Thread Pitch?
The thread pitch is the measurement of threads per inch for US standard wheel studs or the distance in millimeters between the threads for metric applications. US lugs specify threads per inch (TPI), commonly called thread count, so 20 would represent 20 threads per inch. While metric lugs specify a thread pitch which is the distance between the threads. Therefore, a 1.5 pitch would have 1.5 millimeters between each thread.
When searching for lugs you will see the thread size followed by something like -20 (1/2"-20) or x1.5 (M12x1.5). This is the pitch and it's just as important to get right as the thread size. If you get the wrong thread pitch the lugs will pinch when tightening and not fully engage.