when do you replace wheel studs?
 

Yes, I'm sure this has been asked before, but my search didn't turn up much. I was just curious what most guys conisder the safety cutoff point where you should replace your wheel studs after adding wheel spacers. I'd been using some really slim 3.3mm spacers, so I really didn't think much of it. but I finally decided I needed to go a little bigger on the rear because, somehow I started going faster, and I guess the tire is flexing more and it's starting to rub an oil line... which is not good.

Lol, 3.8mm probably would have done it, but they aren't easy to find, and I haven't bothered having some machined down. I managed to find the smallest pair of 6.5mm spacers I could, they're both right around 6mm dead on. I know most people say a 6.5mm spacer is perfectly safe to use with stock studs, but... there's something a little disconcerting about only getting like 8 full turns out of the lug nuts. Good?, bad?, unsafe?, safe? Specifically when tracking the car. What do you think?

The first 3 threads carry over 90% of the load, but regardless of that what I think you should do is get some open steel lug nuts and make sure all of the threads on the nut are engaged, then you'll be in good shape for the track.

Yeah, I very much agree about the open steel lug nuts. I'd ordered a set that never came and then just didn't think about it until recently. Lol, it's a little late for this track event, but next time...

The general rule of tumb is that you should have as much thread engagement as the nut is wide. I assume the pitch of the thread is probably 1.5mm (can someone verify?) so that would mean 8 full turns is 12mm of engagement.

You should have as much thread engagement as the STUD is wide.

I would not feel safe with less than 6-7 turns of a lug nut, but anything more than that is probably OK.

Could you get those spacers shaved down perhaps?

Uh, Terrh

Wouldn't the I.D. if the but pretty much be equal to the width of the stud? :D

BTDT.
When I went to 7mm spacers & steel nuts, the stud didn't protrude the 1.5 threads I like for any nut....in fact, they were about the same amount below the top of the nut. 6 turns IIRC.

The conventional wisdom that I have heard is nine turns for aluminum lug nuts......but were I a track rat, I wouldn't use them at all.

Steel, as mentioned is 1x hole diameter. Aluminum is 2x.

In a strict engineering sense, you are probably right.

In the real world, any fastener that is recessed into it's nut is gonna be questioned and well may be thrown out .....unless you have documentation to back you up and a way to measure it. If I were the tech guy, I'd want to see it all.....sorry, in a sense, it's what do for a living. :D

Where I work, there are thousands of pages of fastener specs. To the best of my knowledge, none allow recessed
or flush threads. Most have minimum allowable protrusion...some have maximum also. *This may be just to make it easy to tell at a glance if the installation is correct.*

"Best Shop Practice" is 1 1/2 threads in a non controlled enviroment and has been since Christ was a corporal.
Guys working the tech line know that. It's good to keep them happy.