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Discussion summary
YOUR RESEARCH3 busted lugs on one wheel
Leading reported evidence
Install 15mm spacers
Performed · outcome unconfirmed
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Performed · outcome unconfirmed · Original poster
When I installed 15mm spacers, it seems at least possible that the lug nuts on the affected studs, when torqued, were at or near the flaw/stress/bad juju I caused/exacerbated at install time.
Leading evidence: 'Install 15mm spacers' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'wheel' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check calibration of your torque wrench' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
I haven't had those lugs installed for more than a couple of years.
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Performed · outcome unconfirmed
Over tightened your nuts.I know they are lugs but I know you prefer nuts.
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Performed · outcome unconfirmed · Original poster
When I installed 15mm spacers, it seems at least possible that the lug nuts on the affected studs, when torqued, were at or near the flaw/stress/bad juju I caused/exacerbated at install time.
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wheel
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Suspected cause · Original poster
I suspect there was a defect in a run of bolts, and that was the wheel that let go first (it's on the heavier axle, on my fat a$$'s side of the car - so it was the wheel with the most weight on it.
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Me thinks your good guys at Discount Tire or Tire Barn or Tires R Us or WTF Tires did one of two things...
1. Over tightened your nuts.I know they are lugs but I know you prefer nuts.
OR
2. Did not torque them enough
Either way that sucks. Have you thought of taking a lug from two other wheels and putting them on the nutless one? Just to get home?
I was waiting to see from whom the first discount tire remark would come.
I was the last person to take off and reinstall those wheels; they were torqued to spec when I put them back on and I re-torqued them less than 2 weeks.
I�m not a complete fsck-up; had I been able to just move a lug bolt from one wheel to another, I woulda.
3 of the lugs sheared off below shoulder level on one wheel; none of the others are busted.
Mice then. They are sneaky. They over-tightened your nuts.
Regardless, JI's curse continues. Your lights don't work, car sets itself on fire if you turn the light on, one wheel got penetrated by a "pointed object", another wheel almost fell off.
Sell the car Dallas.
The scratches are all from the stud remover I used to make sure I could get those out without breaking them off any lower.
None were loose; they all came out as expected. No indication on the hub that anything was moving until it was only running with two lug bolts.
Looks to me there may be some corrosion on the outer edges of that broken stud, indicating it was fractured for a while. No simple task to break one of these. From the shape of the displaced steel shown in the closeup, seems to have been a tensile failure( vs shear).
So, yeah, I'll be waiting for a nice new set of factory lug bolts to show up. That stud conversion set was from a reputable distributor, not eBay.
I've dodged two bullets with the 996 so far...while I love the simplicity of wheel changes with studs rather than lug bolts, the ones that don't break off unexpectedly are probably at least 20% cooler (confound those bronies...they drive me to insomnia).
Dunno if the distributor will want to do anything about it, but I'll let them know what happened.
Re: tensile vs. shear - until that third bolt popped off, the hub was still perfectly aligned with the wheel. There was some scuffing around the last two lugs (presumably because they were flexing, since the two remaining bolts were adjoining). I don't see HOW the first two lugs could have failed in any way except tensile. As far as corrosion, it's a CA car that has seen rain maybe five times since those studs went in.
I suspect there was a defect in a run of bolts, and that was the wheel that let go first (it's on the heavier axle, on my fat a$$'s side of the car - so it was the wheel with the most weight on it.
I haven't had those lugs installed for more than a couple of years. When I look back at some of the driving events and other drives I've done that could have ended in...well, let's just say I feel pretty damn lucky.
I'll take some better photos of the busted studs with my non-potato camera.
Tensile as in torsional load? Beckham's tazer tells me you may have inadvertently over-torqued the aftermarket hardware - not exactly your fault but unfortunately your problem.
A recent over-torquing is an obvious suspect, but I have another theory.
The stud kit I ordered was supposed to have a machined hex socket so an impact driver could be used for installation. These are just rounded on the end, so I had to use two lug nuts snugged up together to be able to drive the studs into the hubs (by hand, of course - I didn't use a rattle gun or anything stupid for installing the studs).
I can imagine the stress concentrations in that specific scenario like I'm staring at the plot. This concentrated a butt-ton of strain onto what, a single turn of exposed thread. I think I screwed the pooch on day one.
Hmm, I can see that scenario playing out. Jamming the two nuts together puts a tensile load on the bolt section between them. On top of that, the load is very concentrated oblong a short section of the bolt. Probably easier to cause yield than we think.
This was a very near miss, lucky! Looks like the OEM bolts are the way to go.
Don't the studs usually have a female hex so you can install them to the correct torque? Interesting that this set didnt.
I will never use rennline studs (or equivalent) on any of my cars. Far too many reported failures.
All of the systems I deal with at work require specialized fasteners. Rennline states their fasteners are all black zinc 'coated.' This is rather misleading as it's not a coating, but rather a plating. During the plating process, high carbon steels are susceptible to a phenomenon called hydrogen embrittlement. Simply put, the material absorbs the hydrogen and it separates/invades the grain structure (small cracks) of the material. This makes it very weak - typically failing via fatigue...the failure analysis should just state, "cad jockeys/mechanics who thought they were engineers."
WowOuch! Just glad the wheel didn't leave the car at high speed. That could have been...not good.
"You picked a bad time to leave me Loose Wheel..."(My apologies. It's late.)
Assuming these are class 10.9 fasteners, you can produce 16,000lbs of clamping force with a zinc plated M14x1.25 fastener torqued to roughly 125ft-lbs.
The nominal stress area for a m14x1.5 thread is about 0.194in^2.
σ=F/A = (16,000/0.194)
σ = 82.5ksi
For a fastener to be certified to grade 10.9, its minimum proof strength needs to be about 136ksi and its tensile strength to be about 150ksi.
This is quick and dirty hand calc that is very conservative, but still proves the scenario you are suggesting is very unlikely.
A good torque vs clamping force look up table btw.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.fastenal.com/content/feds/pdf/Torque-Tension%2520Chart%2520for%2520Metric%2520Fasteners.pdf&ved=0ahUKEwj--63lkrrVAhVK7GMKHbkKB9EQFggxMAE&usg=AFQjCNHQtnuC59iH2tMnGLQSUZ-fT21g_w
That's the same one I used as reference in my post.
In practice, my group uses Abaqus for our FEA. A majority of our systems fall under grade A shock items under MIL-S-901D so all of our torque specs are based on the system meeting customer requirements.
You Tube
After staring at the parts for a while, I think I created or aggravated an issue with my wheel studs when I installed them. This wasn't an issue at the time; the broken studs failed further outboard from the point where the lug nuts were originally snugged. It wouldn't have been an issue, but then...
When I installed 15mm spacers, it seems at least possible that the lug nuts on the affected studs, when torqued, were at or near the flaw/stress/bad juju I caused/exacerbated at install time.
Or, you know, totally not my fault, man.
See my post above regarding the stress you induced vs the material strength. Not your fault.
Glad to hear that you will live to post another day though!
You and...a small handful of other folks on RL.
If I hadn't had the car up on jack stands in the driveway just 2 weeks ago, I'd be wondering how long one or two had been broken off like that. I _almost_ waited to check until I got to a more convenient location, but the sensation was REALLY unsettling. Still makes me a little anxious to think about...
For what it's worth: I went back and reviewed the product info for those studs. They are listed as a "wear item," recommending replacement every 2 years or as needed based on examination for wear. I wasn't even close to the 2-year mark yet.
I should have taken the disclaimer included in those instructions a little more seriously.
It turns out that many things are self-tightening, especially when you hear a stud break and feel the wheel wobbling on the hub. One or two items have yet to un-clench.
The documentation that came with the studs did not mention any limitations or recommendations beyond the 2-year replacement cycle. For the record, even that's a stretch for my car given the guidelines in the install notes...
Wheels studs used in competition are considered wear items and should be replaced on the following intervals
o Street/DE car with less than 10 events a year – Replace every two years
o Race Car with or DE car with over 10 events a year – Replace every year
o Pro level racing – twice a year
The car is not going to be operated until the replacement bolts are here. I wouldn't let my worst enemy drive the car with the remaining studs installed.
Other than the three that were f****g broken completely off, there were no anomalies during disassembly. The broken studs - and the two remaining good studs - all backed out of the hub with the expected amount of effort given the installation method (30 lb-ft plus Loctite 272). Those suckers were certainly not loose.
See, now you're getting into the spirit of scarring other peoples' minds through Google. You need to be a little less restrained, though - 2 girls, one cup is memorable, but not permanently etched into the Interweb's unconscious like Goatse.
When your hand is stocked with sh*t like Goatse, pink socking, space docking, and the occasional rolling brownout, just throw 'em down and watch the dealer lose his job...
I use these wheel guides when changing the wheels. It takes a little longer due to the extra steps, but it makes the process much easier.
http://www.maxspeed-motorsports.com/...Jack_Pad_.html
Check the calibration of your torque wrench. Make sure you were looking at Ft-lb, if it has another unit on the other side. The only time I see stuff like that is when they are not to spec.... then as one breaks loose, it has a domino effect.
Studs aren't the problem. Low quality fasteners made by ****ty companies are. Fasteners are not created equally - everything from how to manufacture them, inspect them, and the spec you certify them to.
I made some prototypes for myself a while back. Age hardened and tempered nickel-copper. (Grade 500 per MIL-S-1222H)
Of the many responses I anticipated possibly getting from the vendor, here's something I didn't anticipate:
"The images did come through this time. It appears that the studs backed out rather that actually failing. I will contact [manufacturer] for their opinion as to the possible cause."
Wut? How can you look at those photos and see "they backed out" rather than "they f****g broke! Holy sh*t!"
Tall gray aliens were bored, so they translocated a tiny yet massive black hole to each stud one-by-one. I don't understand the mechanism by which the studs were slaved to the black hole, but the immense inertia of the black hole temporarily locked the linked stud, preventing it from turning, at the same instant the wheel on which that stud was affixed mysteriously assumed a cycloid orbit with an axis of rotation relative to the stalled stud. So they fell out.
Or I used a stud puller.
Public service announcement: using absinthe in lieu of bong water - and then doing dirty bong absinthe shots - might be a bad idea.
Also with the new non rusting bolts to counter the added spacer weight
Saved the box expecting one day to ship to a member in need.
That the case until a sobering conversation with a salesman
after a Panamera test drive.
Their trade in value offer for the car they sold me 9000$ less than
the purchase price two years and 12 thousand kms later.
"As you please" his response when I told him I'd keep all the
accessories and bits.
Good fortune 5CHN3LL that your stud shear wasn't tragic.
Time to buy a handful of lottery tickets.
I couldn't agree more. When I look back at the various things I've done with the 996 since installing those studs, there are very few I think, "well, I could have done THAT on three wheels."
The guys at Black Forest here in San Diego continue to impress me. On my way to run another errand, I stopped by Black Forest to ask Jeff if I could borrow a wheel's worth of lug bolts for a few days so I could get the car off the jack stands and in the garage. He was even more freaked out than I was when i showed him the photos of the broken studs, and he sent me on my way with a bag of lug bolts to use until I figure out which direction I'm going with the 996 (sourcing alternate studs or running screaming back to the safety of bolts).
TonyTwoBags, thanks again for the offer of the set of bolts. I owe you one.
Just recently purchased a set of new GT3 +5mm wheel bolts, can't really see the advantage in studs. That being said I don't remove my wheels all that often.
Interesting to see people using bolts without a floating collar.
Dont forget the castrol Optimoly TA paste! Which is now called Castrol molub-alloy TA.
Yet another email from the vendor, this time stating that neither they nor the manufacturer have ever seen a stud back out. Apparently, the fact that the studs are actually BROKEN continues to elude these f*******s.
I have gone out of my way to anonymize my dealings with them - it pisses me off when people don't give a vendor an opportunity to make something right. I don't want anything other than for them to look at the damn parts and say "nope, you're the idiot...everyone else will be fine" - but this seems to be asking too much.
If you are running aftermarket studs with your 996 and this thread concerns you, please PM me and I will share the details of the studs I was using (brand, length, spacers, and other details)...
NONE OF THE STUDS BACKED OUT OF THE HUBS.
I know the caps seem extreme, but I've restated this two or three times now.
The studs did not back out.
They FAILED in an incredibly alarming way, and frankly I'm getting a little irritated that I have to keep explaining this.
What did happen, though: Because of an as-yet-undiagnosed equipment failure, 60% of the available clamping force holding my rear wheel onto its hub disappeared; it was lost unexpectedly while I was driving the car.
Had I not felt and heard the studs break WHILE I WAS DRIVING the car, any jolt or even an abrupt corner could have resulted in losing the rear driver-side wheel.
In a car with well over 60% of the weight on the rear wheels, losing a wheel with the car in motion could have been very serious. Had it happened at speed on the highway, the outcome could have been deadly.
Had I not removed all 10 rear studs with two different stud extractors (because I'm probably overreacting about not wanting to die in a fire due to equipment failure), all ten of them would be very securely installed in the rear hubs on my 911. And three of them would also be significantly shorter than they're supposed to be. Because they BROKE OFF.
The lack of any sort of "holy crap, glad you didn't die...sorry the product you bought from us failed in a way that could potentially have ended your life" is disheartening.
Update: After a phenomenal phone call from a Pelican VP (this dude should teach seminars on how to un-f**k customer relationships), it appears that the gentleman with whom I was corresponding earlier (I had written "toolbag," but that's probably inflammatory) was not necessarily treating the situation with the degree of care Pelican might have otherwise preferred.
There are still a lot of questions up in the air. Whatever the cause, assuming it's determined and shared with me - I'll pass it along. At least the vendor appears to be on-board and - as far as I can detect with my finely calibrated BS detector - acting in good faith.
MM, thanks for noticing this thread and putting 2 and 2 together.
I got a credit for the wheel studs, and I continue to run factory lug bolts (5 years later) because they don't break unexpectedly.
Also, necrothread smells like Gnat's mom
[Image-only post; no author-written text. Original image references:]
https://cimg5.ibsrv.net/gimg/rennlist.com-vbulletin/320x240/giphy_31_1c9a2f730da312eaf926751e8cf8a2fab670853a.gif
B3 recently said he�s ok but life is keeping him too busy to spend so much time bailing our asses out of trouble. Or words loosely similar to those. I�m waiting to ambush him with about 3 years worth of questions if he pokes his nose back on our little RL soir�e. Hmmm, yup that�ll learn�m.
Yea, since he took classes from the Knowledge Gruppe, I had his contact information. I reached out to him and he responded very quickly. He told me that since the pandemic that his work schedule and demand have changed. He didn't have the spare time to come on RL, but wishes us all the best!
Here is cc from his email:
[snip]
Thanks for checking on me and hope my email finds you well! Yeah, I've been very busy with life and couldn't spend much time wrenching and checking the Porsche forums. I've been working from home since the COVID hit hard on the states and expect to WFH for at least the coming half a yr.
Please help me say "Hi" to them when you have a chance.
Best regards,
Duncan
[snip]
lol. That picture was taken March 18, 2020. I remember it well because it was the very first day of what is now 18 months of telecommuting for me.
I don't live in LM but I'm there several times a week for work and I have a rental at Smoke Tree by Baltimore & Lake Murray.
Sorry for what might be a stupid question, but what is the motivation for switching from the stock lug bolts to studs and nuts? I've never heard of any problems with the original bolts and it seems like the studs and nuts have a lot of issues.
I think the "wear item" comments apply only to non-stock studs and nuts, not to the original lug bolts that came in the 996.
This is a source reference. Confirm exact model applicability in the original material.
