Wheel studs are the securing point between the rotors and wheels of your vehicle. Knowing the size of your vehicle's wheel studs ensures that new wheels will fit, replacement wheel studs will work with your current lug nuts or that replacement lug nuts will thread onto your existing wheel studs. One measuring method requires no difficult-to-read machinist tools.
Set the vehicle parking brake.
Turn each lug nut of one wheel 1/2 turn counterclockwise with a lug nut tee-handle.
Jack up the vehicle with a floor jack. Place one jack stand on each side of the lifted vehicle to keep it stable. Leave the floor jack in place.
Turn each loosened lug nut counterclockwise by hand to remove the lug nuts from the wheel studs. Remove the wheel from the vehicle.
Place the flat face of a bolt gauge against a wheel stud. Move the bolt gauge until a wheel stud slips tightly into a hole. When the bolt sits in the hole and does not allow the gauge to move from side to side, you have the correct-sized hole. Read the size of the hole to determine the stud diameter.
Slide the bolt gauge off the wheel stud. Move the bolt gauge to align a threaded hole with the wheel stud. Turn the bolt gauge until the gauge threads onto the wheel stud. Read the numbers near the hole to determine the thread count of the wheel stud.
Set the zero end of the bolt gauge against the surface of the rotor. Read the number where the stud ends. This shows the stud length.
Replace the wheel. Thread the lug nuts onto the wheel studs. Remove the jack stands from under the vehicle.
Lower the vehicle with the floor jack. Tighten each lug nut with a lug nut tee-wrench.