Axle studs-stock length or 3"

The
thread engagement on all wheel studs to the lug nut, or lug bolts to
wheel hubs, must be equivalent to or greater than the diameter of
the stud/bolt. Length of the stud/bolt does not determine
permissibility. (Example: A 7/16-inch stud must be thoroughly
engaged through the threads in the hex portion of the lug a
minimum of 7/16-inch.)


as per NHRA 2012 rule book...