I have a 91 Z 28 Since I am running slicks on a set of Weld Pro Stars rims I have to have extended Wheel Studs by NHRA Rules so I know they say they dont have them in the 12mm size so what is the size and knurl of the stud do i need The sizes that i can get is 7/16" x 2 7/8 long with a .486" knurl or one with a .580" knurl. And what is the size of drill bit so need to drill the new holes any info will be helpful thank you.

 

When you buy need studs they'll come with instructions as to the size of hole to drill. Go slightly smaller.

Don't use 7/16 on the rear. Buy some 1/2" x 3" studs.

 

Check out the link in the sig and see if the picture of the lugs are what you need. Drop me an email and I'll get you the GM part number for them. I have it at home.

 

ARP makes the studs you need,the part number is 070-100-7708.I have bought 4 sets of these for my Z,all 4 wheels have extended studs.They do need to be pressed in to the axles and rotors,but no drilling is required to get them to fit. go to http://www.jegs.com they carry them,that is where I, got mine from.They are $13 a set.

 

i just put in Moroso extended studs today, 7/16 x 2 7/8 with the smaller knurl for my 84 Camaro, didnt even have to remove the axles, used a small sledge hammer to extricate the old studs, then, find the deepest spot in the backing plate [by the emergency brake line] and feed the new studs in from there. [for the rear that is] The fronts i'll have done tomorrow while im getting new drag springs installed.

 

Whats NHRA rules for studs Stephen? Its like 3/4 way into the nut for IHRA.

-- Joe

 

The rules state that the stud must extend a minimum of the diameter of the stud into the hex portion of the nut.

Simpler terms.

A 1/2" wheel stud must extend at least 1/2" past the surface of the rim. If you have open ended nuts, the stud should stick out the nut.

Once you start getting into special rims like Weld Drag Lites, you need long studs and special nuts for the rims. Since the nuts are usually longer than the studs, the studs don't have to extend past the nut but must still extend into the nut far enough that there is enough thread holding on.

If in doubt, use longer studs than required. If you have capped nuts that you can't see the end of the stud, tech may ask to have a nut removed for stud inspection.