Jawnathin

Just got a set of open ended lugs and I understand one of the key benefits is that you and/or tech inspectors can do a quick visual 'test' to ensure there is proper thread engagement with non-OEM wheels, especially in circumstances where spacers are required.

I believe the 'rule' for ideal thread engagement should be equivalent to the diameter of the wheel stud. So for our cars, its 12x1.5. 12mm diameter wheel stud with 1.5mm of thread per rotation. Now since we have 1.5mm of thread per rotation, in order to get 12mm of thread engagement, we need at least 8 full rotations.

8 rotations x 1.5mm = 12mm of engagement

Okay, so with that out of the way, when a tech inspector does the quick visual test, at what point should it pass, fail, or be considered questionable?

Someone I consider to be very reputable, but to their credit wasn't 100% sure, thought that the wheel stud needed to stick out beyond the open lug. Many of the cars in the pits had that. Not sure if that was because it was required or they ended up with wheel studs way longer than they needed, or had 'thin' lug nuts.

And frankly, I'm not sure what benefit protruding studs will serve over a wheel stud that was 'flush' with the end of the open wheel stud. After all, if the wheel stud was near the end of the open end of the nut, then all of the threads would be engaged anyway.

I've attached photos of both my front and rear of my setup along with a photo of the lug nut that I use. For anyone who has done tech in the past, how would you rate this?

FWIW, I get about 12 rotations up front (18mm) and 8 rotations in the rear (12mm) of thread engagement with this setup.

Thanks.

froggy47

I would pass those.

chetly

Yeah, I don't see any racing sanction not passing those... But just to be sure, we should see the whole car with wheels installed.

Jawnathin

Thanks both of you for the feedback. I don't see why it would be a problem, just the information I got from a friend gave me second thoughts. Was looking for a second opinion on the forum about the topic.

Not sure how a picture of the whole car will help, but here you go. Thanks.

Black89Z51

Do your studs have missing threads at the very end? I prefer that part to be sticking out of the lug nut, but that's just me.

Jawnathin

The rears have the 'blank' part without the threads. Its about 1/4" of an inch. This is how OEM is setup.

On the fronts I've got the DRM 1/2" longer studs (1/4" longer, 1/4" blanks are 'filled'). They are filled to the very end.

That is why I have 12 rotations up front and 8 rotations in the rear.

Kubs

The rule of thumb for ANY fastener is 1.5 times the diameter for thread engagement (18mm in your case). I also would not count the turns, but measure the length of the threads. Put a marker on the threads before you put the wheel on and then when you install the lugs it should wipe away most of it. Take the wheel off and measure how much was taken away and that is your thread engaement.

Based on a visual check they look at least as good as OEM, but OEM is not always the best for track conditions.

Jawnathin

You can measure thread engagement based on the number of turns. Our studs are 1.5mm per rotation, so 12 rotations would give you 18mm of thread engagement.

Thanks.

froggy47

Many gm oem are missing threads at the end because, who knows, seems stupid to me.

Point being, as quoted above, if they don't stick out a little you don't know.

hklvette

It makes it easier to get the lug nuts on properly instead of sideways.

Jawnathin

I also figure there is less wear/damage to the threads when mounting wheels too.

UstaB-GS549

A standard M10x1.5 nut is 10 mm high which translates to 6.7 revolutions of thread engagement. You don't need any more than that to tension the wheel stud.