I was changing out my DRs for winter driving today, when I noticed there's about 2 threads less engagement of the lugnuts on the rear wheel studs compared to the front. I have Superior aftermarket stock replacement axles and it looks like the wheel studs are shorter than stock. I have stock wheels and stock lug nuts.

I've been driving it this way for over 5 years - just noticed it today - question: is this a safety problem? Should I have the rear wheel studs replaced with ones that are longer?

 

The requirement for safe thread engagement is that the length of the thread engagement, in the hex portion of the lug, should be "one diameter" of the stud. In other words, with 12mm or 1/2" diameter studs, you want 1/2" of thread engagement. More is OK. Less is not good. If you have at least 1/2" of threads on the stud engaging 1/2" of threads in the lug, you are OK. That requirement includes some sort of "safety factor".

 

Thanks, Fred. In my mind's eye, it seems like there was less than 1/2 inch of thread engagement. I'll go out tomorrow and measure it.

 

Do your replacement axles have press-in studs or threaded?

 

I don't know. Would it be obvious when I get a wheel off, or is there some other way I could tell? (haven't had a chance yet to measure it)

 

If they are knurled/press-in, the heads will be flat and round. If they are screw-in, the heads of the studs will have a hex head so you can tighten them into the axle hub flanges with a wrench. One reason for asking - the threaded ones will sometimes back out a little when you tighten the lugs, leaving them a bit shorter than they should be. A little lock-tight and periodic tightening helps with the screw-in studs.

 

Great info, thanks again. Looks like I will have a chance tomorrow (going to be in the 60s) to check it out.

 

Well, this certainly doesn't bode well... the studs are press-in, and the amount of thread engagement is 0.31 inches (measured pretty carefully with calipers).

Time to replace the studs?

 

Seems very short. How long are the studs? I'll measure the factory ones when I get home.

 

Stock press-in stud is 2.14" overall length.

Unthreaded end: 0.34"
Threaded length: 1.15"
Shoulder: 0.19"
Knurl: .30"
head: .16"

Assuming the knurl fills the thickness of the hub flange, the projection of the stud would be 1.68"

 

This does not look too good...

The total projection of the stud is 1.09". The unthreaded part is approximately 0.38". This leaves the length with actual threads of approximately 0.71" -- this is a full 0.40" shorter than stock! I wonder how these "stock replacement" axles (from a reputable company) could have wheel studs this short?

I am quite certain that the stud is fully pressed in from the back.

 

Just get a set of ARP 3" studs, I think they are $8 a side. Just poound the current studs out with a hammer, and pull the new ones on with a lug nut and some washers stacked behind it (note an impact wrench helps alot). I would however get a couple of extra lug nuts, you will probably start chewing up the threads in the lug after 10 studs.
Good Luck.

 

I think you're right. It's worth changing them out just for the peace of mind. If the current studs are so marginal, I'm thinking why take any chances...