I need to buy a socket so I can check the torque on my lug nuts. I have the 18" wheels.

Is the size 13/16" or is it metric? I assume I'll need a 6-point deep socket?

 

It's a 13/16". I use a 12-pt standard depth with a short extension but a 6-pt deep would work too.

 

I started to use my 13/16" standard 12-point socket but it wouldn't go on all the way and it started marring the lug nut.

 

21mm socket

 

21mm = .8268 in.

13/16" = .8125 in.

Looks like 13/16" would be the tighter fit.

 

I can't get SAE sockets here and the 21mm fits the lugs with no movement.

 

They are 21mm for sure. All fasteners are metric on cars now have been for a long time.

 

I use the 13/16 no problem. But hey a back up is always handy....

 

And that's why the wheel studs and the internal thread of the lug nuts are 1/2"-20, correct?


The proper size socket for the lug nuts is 13/16".


A 21mm 6-point is a sloppy fit but will work if you want to mar your pretty lug nuts.

 

I have two 21mm sockets that fit perfectly, and 3 13/16th sockets that kinda-sorta fit.

 

Whatever floats your boat is fine with me. Just telling you how it really is.


Try shopping for some Mustang replacement or custom lug nuts. They're all listed as 13/16" on a 1/2"-20 stud. It's been that way since at least the 70s and continues through 2014.


You can use a 21mm socket (0.827") and I have myself, but the 13/16" (0.813") is correct.


Just like your wheels are 18" (457.2mm) or 19" (483.6mm) or whatever, not everything is metric as redmsgt said.

 

I'll vouch for you. They're 13/16".

 

13/16" 6 point deep welll 1/2" socket here.

I test fit the 21mm and man, that is going to round off them lug nuts. Don't do it unless you have to.

 

Are the lugs a chromed steel nut or are they the other style dressed up plain old lug nuts with a stamped stainless steel cover for dressup? Are the nuts "beat up" any at the corners like an air wrench does when the guy at the tire shop hammers on it? If the corners are misshaped due to loose fitting sockets or pneumatic wrenches, a 21mm might seem to fit better, but likely will aggravate the situation under torque loads with a torque wrench.

Our Mustang and all our other FoMoCos with 1/2-20 studs use 13/16" very well and on wheel lugs, I always always use 6 point deep well sockets (the two Thunderbirds use 3/4 but they have 12mm metric studs) and a torque wrench for tightening.

 

I agree with tbear853. If they're the nuts with the stainless cover on them they can be distorted by using a shallow socket, which doesn't normally reach to the bottom of the stainless where the actual shorter inner lug nut is. A deep 6 pt. socket is the best choice to keep distortion to a minimal.