Tech inspection should be visual only. If they want to check the torque on my wheels I have required them to use my torque wrench

Peter

 

I've stayed with the factory bolts (with the dish washers that match the curvature of the wheel), so I have no first hand stud data, but I'm an engineer, and my best guess is that the studs are getting significant scratches in them, perhaps caused when mounting or removing the wheel. Scratches are stress risers, and they, coupled with a bit of overtorquing, might be the root cause.

 

Agree with Peter. I do NOT let them torque my wheels anymore. Mine are torqued to 96 and then you pull up in line and they have their torque wrench (that has probably never been calibrated) and instead of checking for the "click" they actually apply force with a fast rotation (since they are in a hurry) which gets you the "click" as well as more rotation of the nut resulting in a higher torque value.

 

I agree that a scratch or some surface impact could create a stress concentration that could lead to failure. However in my case, the stud broke a couple of threads inside the hub, so there was no way for a scratch to be inflicted and propagate. I'm starting to think that a couple of over torquing events contributed, but also suspect that there was a flaw in the stud given that it had apparently been cracked for a while.

 

This has been discussed before here. I broke 2 apex studs on my left rear wheel last Fall. They broke just below the surface of the wheel carrier. I used red high temp loctite, but they were easy to extract. I am the only one who mounts my wheels, and I tighten them by hand, although I use an electric gun to loosen them. However, they buggered the threads of the wheel carrier. Eventually, had to replace the wheel carrier. Now, I'm back to lug bolts..PITA, different lengths with different wheels, but none have broken. The Apex (Bilden) studs I used were rolled. Also used their cut ones, which also broke.

 

1- Studs break within the wheel carrier, so scratches are highly unlikely
2- Most seem to break on the left rear... WTF?
3- Sorry John, but you'll have to get in line for the wing
4- Except for my second failure, which had been overtightened (but may not be relevant?), I am very careful when mounting the wheels. Always breaker bar to start the loosening, always the torque wrench to finish the tightening, impact driver strictly used to speed up the process in between

5- Major difference between bolt and stud, as pointed out by plima, is that bolt has the spherical dish washer/spacer under the head. Wouldn't this contribute to reducing the twisting force that is applied to the bolt? IOW, the bolt is then only subject to a pulling/stretching force, whereas the stud would also be subject to a twisting moment on top of the pull???

 

John, aren't there only two types of nuts? Spherical and conical. I doubt that many owners are using conical nuts?

 

From an earlier discussion:

"When I get home I can post which studs I had to run on the GT3 that worked with stock, Fikse, and BBS E88. I am 100% certain they were BBS studs but I'll get the exact dimensions when I get home (BBS 65mm 14x1.5mm). For 2 studs to fail on one hub, sorry Chuck, but that would almost certainly point to user error or possibly a bad batch.

Not trying to single you out Chuck but the studs can fail very easily from the torque generated by the wheel against the bolt and if there is not enough thread engagement at BOTH sides (wheel and hub) it can get ugly quickly. It could also be something as simple as forgetting to torque them down.

To think that bolts are safer than studs is anecdotal. Think about how the stud engages the hub the way a bolt does. The length it goes into the hub, and the way it is secured. Very little difference.

When ordering studs you need to make sure that not only is there enough thread engagement with the nut (so longer would be better) but also enough engagement at the wheel and hub. Some bolts shoulder is longer than others. For example, there were certain studs I could not use with Fikse that I could with BBS and vice versa because of the way the wheels are made and the thickness of the wheel centers.
__________________
Cheers,"

After hearing about so many other people having the same problem, I feel vindicated...

 

To say you feel vindicated is like the guys in the 996 forum that have an IMS failure call the entire line plagued.

I have run studs on multiple cars with countless wheel changes and all cars were 100% hard track duty with not a single stud ever failing.

As the quote you referenced stated, you need to make sure that the depth the stud goes into the carrier, the engagement of the threads at the face of the wheel, and the length of the stud are all the proper dimension. In addition, torque values, gaps, metal fatigue, etc, etc, etc, all come into play.

To move entirely from studs to bolts because you had 2 bolts on one hub break is 100% irrational without knowing all the factors that led to it. And truth is you do not.

 

My asking what the OP torqued the studs to was not asking what they should be torqued to. I was curious if he may have went over the correct setting. 15-17lbs is all it takes to snug these into a hub. Also, I hear people all the time at the track torquing lugs to 95-100lbs because they think the additional beating the car will take on the track warrants tighter wheels. This is not true. While stock specs may be 95, 85-90 should be more than enough to do the job from a physics standpoint.

Also, I have seen terrible things come from people putting anti-seize on lugs. Never ever ever do this. It will keep you from getting any sheering force on the studs and seating surface and not show an accurate load on the bolt, causing severe over-torquing and inevitably a failure.

 

Not to be argumentative (if that is possible), I feel vindicated because I was told that it was "almost certainly user error". I made sure of all of the things that you mention. It would be 100% irrational to experience a near catastrophic failure and continue with the same practice because I am not certain of the root cause, when with an alternate method, I have not experienced the failure.
Sometimes, I don't know the answer. In those cases, I don't claim to have the only explanation.

 

Not to be argumentative (if that is possible), I feel vindicated because I was told that it was "almost certainly user error". I made sure of all of the things that you mention. It would be 100% irrational to experience a near catastrophic failure and continue with the same practice because I am not certain of the root cause, when with an alternate method, I have not experienced the failure.
Sometimes, I don't know the answer. In those cases, I don't claim to have the only explanation.

 

You can say that again Not argumentative at all. Just a healthy debate to try and get a resolution for all of us if that is possible.

My 2 questions to you would be:
1. Was that your first set of studs or did you run studs before on the car?
2. Did you immediately go to bolts after the stud failure?

 

Oddly enough, I've had an IMS failure requiring a new engine and multiple stud failures

As for the bolts, I can remember 4 in the last year. 1 was a front, and 3 on the rear (2 on the same wheel at the same time). The front simply snapped when changing the wheels out. One rear seemed loose in the wheel carrier, but it turned out that it was starting the shear, so I replaced it. I noticed the other two were broken when the car felt like it war driving on cords so I came in to notice that 2 bolts were sheared at the hub. That was scary as it was just a lap or two and I would have lost a wheel for sure!

Unfortunately, these things do break, just hope yours last as long as Dell's or if they do break, hope that it happens in the paddock.

-td

 

Damn! Your bad luck quota is done. Got it out of the way early