You broke the stud by constantly overtightening, you found out its limit. DON'T grease the studs! Just clean them with a wire brush or wire wheel.
Why did this wheel stud break? Metallurgy issue?
- Thread starter berniedd
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You broke the stud by constantly overtightening, you found out its limit. DON'T grease the studs! Just clean them with a wire brush or wire wheel.
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I use a little grease on the studs but I also use a quality torque wrench and back off the factory setting by 20%. I know, what I'm doing is guesswork, but it makes sense to me. Been doing this longer than some young ones been alive. My car, my wrench, my choice. I sleep well at night. Never had any issues. You have fatigued your bolt to the point of failure by your inaccurate method of tightening. As other posters have well spoken, replace them all and buy a good torque wrench, before bad things happen while you're driving. Not funny, and if the truth hurts maybe it needs to. The life you save might be yours. I wish you well and hope you heed the healthy warnings you've been given.
Edit: twice in my driving experience I've seen wheels fall off on another car at highway speed. Both times no collisions occurred because other drivers were at safe distances, but it wouldn't surprise me if the drivers needed to change pants.
Edit: twice in my driving experience I've seen wheels fall off on another car at highway speed. Both times no collisions occurred because other drivers were at safe distances, but it wouldn't surprise me if the drivers needed to change pants.
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How did those tires not blow up?
Absolutely- bought tires at Walmart about a month ago. Based upon my experience there, became suspicious of their competence. Got home and checked wheels. Took ALOT of force with a two foot long breaker bar to loosen some lugs. Not only that, but some of the lugs were rounded so that a socket would not grip well. Walmart replaced the lug nuts after alot of complaining.Most mechanics and tire shops overtorque the lug nuts
They zip it with an air gun 600 lb ft of torque or more, and usually torqued unevenly, too.
In general, I believe torque values assume a lightly oiled (not dry) fastener. IMO, lube is okay for wheel stud threads provided none is applied to the cone portion that contacts the wheel. My Porsche owners manual says to apply "anti seize paste" to threads but not to the cone. Porsche cars are built for serious racing and I think Porsche knows a thing or two about attaching wheels. Good enuff for me...
Porsche is unique in this regard.
For many other cars, Mercedes, Volvo, Toyota, to name a few, the torque values specifically state “clean, dry, unlubricated threads”.
You are right. I researched the lube on fastener topic and found that torque values are not affected if applied to the threads only. Values are affected if lube is applied under the bolt head. Seems counter intuitive. My can of Permatex anti seize says to apply it and use the specified torque values (no reduction in torque). Their web site says the same. Perhaps Permatex knows something? I think MB and others specify dry unlubed threads to avoid ppl slathering lube all over threads and cones to play it safe and avoid liability. I forget the company name of a lug nut manufacturer/supplier that says lube on the lug nut threads is okay but not on the studs themselves. I guess this is to avoid getting any on the cones?
Regarding the lightly lubed threads, tables of torque specs for various bolt sizes and grades state lightly oiled.
This is all too complicated for such a simple concept. I see both recommendations from reputable sources.
No reflection on your research but your source(s) is simply wrong. Makes no difference who says otherwise.
If the COF changes ( for any reason) then torque ( turning force) WILL be affected to a degree. That's simply physics and an engineering constant- that's an inarguable fact.
In fact, they do and here it is. "Torque" is a twisting force- a fastener requires TENSION to properly secure a joint. ( they are NOT the same)
PT knows that you don't reduce the TENSION by "fooling" a wrench because now it turns "easier" because of a drop of oil because that will affect the mechanical integrity of the joint.
It is relatively simple in concept but a bit more complex for "critical fasteners" but made confusing because of the (probably well meaning) misinformation out there.
Lubrication reduces the torque necessary to apply a given tension on the stud (clamping force). Lubrication combined with exceeding the recommended torque will greatly exceed the expected tension.
That said, sloppy workers in tire stores love to grossly overtighten wheel studs. Usually they survive that abuse, the safety factor is so large.
That said, sloppy workers in tire stores love to grossly overtighten wheel studs. Usually they survive that abuse, the safety factor is so large.
Thank you ABN- you always have good comments . I know all this from SOM class and agree, but the operative word is "degree". Yes, cof is reduced but how much? If you agree Permatex does know "something" and they say to apply their AZ wo reducing torque, what does this say regarding "degree" or "physics" ? Bottom line is - it doesn't matter
The discussion was about lubing wheel studs and I claimed it was ok to use lube but it went sideways. Not arguing physics although we can if you want. Even equations ...LOL
All 3 Permatex Anti-Seize products say "WARNING: Not for use on wheel lug nut or stud applications." in their respective TDS.
They do all say to 'use normal torque values', but that is very much at odds with what everyone else says, including a company owned by the same group (ITW) as Permatex:
A deeper understanding of Anti-Seize - ROCOL
In this article on anti-seize we talk all things gaskets, torsion-tension relationship, torque settings and get into the nitty gritty of the K factor and friction coefficient.
www.rocol.com
"Because the use of an anti-seize changes the torsion-tension relationship of a fastener system, torque settings need to be recalculated."
Last time I specifically visited Permatex site to check this out, it did not contain that "warning" or I missed it. Otherwise, I would not have mentioned it. Good to know. Thank YouAll 3 Permatex Anti-Seize products say "WARNING: Not for use on wheel lug nut or stud applications." in their respective TDS.
They do all say to 'use normal torque values', but that is very much at odds with what everyone else says, including a company owned by the same group (ITW) as Permatex:
A deeper understanding of Anti-Seize - ROCOL
In this article on anti-seize we talk all things gaskets, torsion-tension relationship, torque settings and get into the nitty gritty of the K factor and friction coefficient.
"Because the use of an anti-seize changes the torsion-tension relationship of a fastener system, torque settings need to be recalculated."
I believe that quote regarding recalculating torque settings probably rightfully applies to anti seize applied under the fastener head, not the threads themselves. I would like to know.
Permatex's list of recommended uses could easily include lug nuts. In my opinion, that warning was probably added for liability, not because of technical unsuitability. Every page in the my Porsche OM has multiple warnings about this or that and for them not to forbid use of "anti seize paste", but instead recommend it, on lug nuts must indicate Porsches confidence in lubing lug nuts.
Please follow the manufacturer recommendations for your vehicle, not what people on these forums think. These are all just everyone's opinions.
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Do Porsches uses special or proprietary wheel studs and lug nuts ? I'm confident that they don't so from a mechanical standpoint, lubing a Honda, Ford, etc won't be any different.
You're welcome.
"Proper bolt torque is required to achieve appropriate bolt tension and elongation. Torque must over come all sources of friction before elongation can occur. Thread and bolt-head friction can be reduced and made consistent by adding a lubricant.
Required torque calculations for proper bolt elongation are made based on threaded fastener geometry and friction of thread and load-bearing surfaces. The friction factor applied to torque calculations is referred to as K-Factor. Both thread and bolt-head friction coefficients are used to calculate K-Factor, so it is through lubrication that friction and K-Factor can be controlled to ensure proper bolt tension and elongation are achieved for a derived torque value.
In assembly, the torque energy is first consumed by overcoming friction. The remaining energy is consumed by bolt elongation (which provides the clamping force). Without proper lubrication, too much torque is used to overcome friction, resulting in insufficient bolt elongation."
Italics mine, from the Molykote folks in this PDF:
Agreed.
If Porsche says to apply anti-seize to lug nuts then recommended torque would be derived accordingly, not using anti-seize could result in under-torqued lug nuts!
Well, I use just a tiny wisp of anti-seize on clean threads. And my Bonney...
Thank you, here is the plain simple truth. The much vaunted "K" factor is virtually impossible to properly calculate in the real world because of the shear number of potential variables and even if you do magically calculate it, its meaningless- see next comment.
Oh it certainly DOES matter and here is the "unwritten" part of what they know.
A bolted joint ( critical fastener obviously but then again if it wasn't "critical" then they wouldn't go to the length too publish a torque spec) is comprised of 4 distinctly different and NOT related parts in relation to a CLAMPING FORCE. ( the word/ action of torque is nowhere in this calculation)
The strength of the fastener ( grade, coating, wet /dry etc)
The physical mechanical properties of the joint materials ( density, geometry, hardness, compressibility etc.)
The class fit ( thread and hole)
The forces the joint must withstand.
Failure of any one of those will "negate' the magic torque ( even if it was correct) and it is COMMON ( since the fastener is normally but not always the single strongest part of the joint) that the "torque' rating of fastener will DAMAGE the joint if maxed out. ( this can also lead to wear/deformation/stress of parts of the joint rendering the "torque spec' meaningless)
"Torque" ( and the ever "bigfoot like" "K" factor- always sighted but never captured) doesn't even factor into any of them.
The only reason a torque specification even exists is because engineers design enough into a joint to where ( all things being to design spec) that a torque wrench can "realistically" tension a fastener if it hits that magic number.
Real critical fasteners do not even ALLOW for torque and either UT or thread count/indicator has to be used.
That's the other part companies like PT "know' so they wont risk legal liability for loss/damage/injury by publishing clear concise wording that could hang them if specifically followed. They don't know what type/grade fastener you are using nor do they know the joint design or condition.
They sell their compounds as anti-galling/corrosion products- not to influence fastener tension.
Hope that cleared it up better
They could just be spec'ing a low torque number, expecting to get the same clamping force. Or using a yet larger stud that is capable of taking the higher clamping force.
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Was surprised (just a few days back) when DT said you have bought x number of tires for that car (130k) … the studs look good but showed me the lug nuts, not so much. They sold me a set for no more than I could get them across town.
There are quite a few posts here suggesting that shops are not properly torquing wheels. I always see them spin them on with a low impact air driver then finish off with a hand torque. Every single tire shop I have been to since I remember in the early 90's has done this. When I get the vehicle back I go around it and check each nut with my fingers and drive home. I check a few at random and they are always in spec.
As far as lubricants on the threads, simply reduce torque by about 25% and you are golden. There is no magic science to it. Repair Engineering has a comprehensive chart that is very useful for just about any fastener you come across:
As far as lubricants on the threads, simply reduce torque by about 25% and you are golden. There is no magic science to it. Repair Engineering has a comprehensive chart that is very useful for just about any fastener you come across:
Bolt Torque Chart
Bolt Torque Chart showing suggested torque values and corresponding bolt clamping forces for various sizes and specifications of fasteners.
www.repairengineering.com
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