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Lug Nuts

Thanks to Buford

Factory lug nuts are 12mm x 1.5 thread (60 degree cone). They use a 19 MM wrench but a 3/4" will work in a pinch. McGuard locking lug nuts are a dealer installed option. (19 MM ~ .7480") Using a true 19 MM will eliminate some lug nut rounding especially if you use a quality socket.

The factory uses what is called a two piece Safety Nut. It only looks solid. A thin sheet medal cap covers the end so that even if you had a small stone or something in the closed lug nut it would seat on the cone and not the top of the stud. Under torque a "tall" stud will rupture the end cap.

Mr Lug Nut makes nice lug nuts that have a larger cone (Part No 5455) that will not gouge the wheel, a set of 4 costs $9.50 at NAPA. They are not safety nuts but they don't seat on the stud top or rust out so easy. 

I keep a 24" 1/2" drive breaker bar in my trunk along with a 1/2" drive torque wrench, 6" extension and 19 MM socket. The factory rims have little room for thick-wall 4 way wrenches. 

I use a cheap 2.5T floor jack at home to rotate tires. Putting a short section of 4x4 under the rocker panel protects the paint and adds lift. Using the forward lift point located under the A-pillar you can lift the whole side of a car at a time to make rotating tires easy to do.

The factory jack is a toy with a tiny base. It will work IF you are on firm and level ground and remember to set your parking brake. It's like surplus parachute, pray you never have to use it. I have dropped my SHO off this Piece of synt jack so the moral is if conditions are not right call AAA or carry a better jack. Either is cheaper than dropping a SHO.

Early SHOs have a reputation for warping rotors. This problem can be all but eliminated if you do 3 things.

  1. Torque lug nuts to 90-105 Ft-Lbs in a star pattern.
  2. Check lug nut torque again in a week. 
  3. Anytime someone else removes your wheels check their work. They can over-tighten, under-tighten, or just get "most of them" like they did on mine last time.

These simple steps can eliminate a lot of expense and trouble.

My summer aftermarket rims hide the lug nuts so I can use open end nuts. Again the larger cone lug nuts from Mr Lug Nut called "3/4" Bulge Conical"  (part no 5355 - 12mm x1.5) are much kinder to wheels and give more reliable torque values. If you can use them I recommend them.

The wheel studs I got were M12-1.5R. Same for SLO & SHO.

13.35 Knurl Diameter, 48.0 Length but that is probably more than you need to know.

-Ron Childs  '91


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