It Happens

[schmidjo]

Hadn't checked this thread in a while. Tempted not to say anything more, But what the hell, enjoy: It bugs me that there is some misinformation here. Mainly this is wrong: 1. Characterizing that "using-lubricate-on-lugnuts” is “dangerous” or “that it will cause the lug-nuts to work loose” is not correct. Generally the opposite is true. And 2. With regards to lubricated contact faces and threads: Under load, the pressure is so super-high that there is no “hydraulic film/barrier”, ok yes in the little valleys of the topography, but otherwise its Metal-on-Metal.

I am not making this stuff up, I am referencing the third edition of "Introduction to the design and behavior of bolted joints", by Bickford (to accurately write this post I went into the office to grab the book ). To quote “The subject is a complex one, which is why a text of over 900 pages can be considered only an introduction.” [As the author says in the prefaces, since the 1981 first edition there has been a lot of feedback (two-way learning) as his book and training classes have been the catalyst for interaction between him and engineers in aerospace, auto, marine, nuclear, etc, industries. I consider the info in this book to be the final word. Although Bickford admits we are still learning, and that any bolted joint can have its own unique challenges (if critical, test or for this situation, wheels, check), what he and colleagues have compiled, and present, is very impressive and comprehensive.]

Another quote "Note that most joint or bolt failure modes are encouraged by insufficient bolt tension and /or insufficient clamping force. Self-loosening, leakage, slip, separation, fatigue— all imply too little clamp.”

So this is why I use lubricate, with the correct torque, I then know I am probably tight enough, consistently, from bolt to bolt. (I also understand the safety factors already built in). Clean and dry, nice chrome or coated surfaces, correct torque, checked often, yes we’ll be OK. The problem is down the road, the range of friction is much higher with old dry maybe corroded fasteners. Yes, believe it or not, you can get a dry coated fastener that is every bit as slippery as a greased one, but you can also get a dry one (wore out coating etc) with too much friction and thus crap tension. And even worse if it galls. My recommendation: at least use some light oil or corrosion protectant spray. Since in addition to affecting friction, corrosion doesn’t do any favors when it comes to stress risers / fatigue.

Book Quote “Bickford’s little known First Law of Bolting: Most bolted joints in this world are providing less clamping force than we think they are”. And “If certainty you need in a clamp, Just make sure those bolts are damp”.

Comments about overtightening / over-torqueing. Look: that’s a separate issue. If a shop is using a rattle gun, from other posts its sound like they can go way overboard (3x to 5x is just stupid), and yes of course reduced friction will exacerbate the issue. In order to reasonably discuss this, we have to at least assume the correct torque is being used! [What this tells me though is that when I use a shop, I’ll have to warn them, try to wipe it off, tell them just to ‘snug it &park it’ and let me torque... Imagine trying to explain this information or pulling out a 900-page book, nope, not going to happen… It’s hard enough typing it up for this post.]

Some math to check the tension in my studs. From a table in Bickford ("to be used with caution /for information only") : the Nut factor for moly grease (from someone’s testing for their particular application) is .10 min, .13 mean, .18 max (black oxide dry is listed as .109, .179, .279). Tension-torque relationship: F=T/ (d*K) = 95 ft-lb*12 / (0.5 * .13) = 17538 lbf. Versus approx. max force limit: Min YS=130ksi * Area 0.16in2 = 20800 lbf. So I am Ok using the mean nut factor, but pretty damn tight. If I use a 0.10 nut factor, I get 22800 lbf. Ouch. So maybe I’ll drop the torque a bit, but I am still safe (because I also do this by feel, didn't break them but they've also stayed tight. Confession: I haven’t used a torque wrench yet on the trailer lugs). [I also checked Machinery’s HB, it lists nut factor 0.3 for non-plated black finish, 0.2 for zinc plated, 0.18 for lubricated, and 0.16 for cadmium plate. So, me using 0.10 is probably an unlikely low nut factor(~friction), and the actual tension is likely to be lower.]

Thus this Book quote: “A completely trustworthy nut factor (~coefficient of friction), therefore, is like the Holy Grail – something everyone yearns for, but which no one will ever find” and “the operator [of the wrench] can be a more important factor than all of the other factors combined” [for establishing preload with torque].

As long as I am making this post. A story from my Dad: late 1960’s he drove a welding delivery truck, always overloaded, and lugnuts would loosen; they would have to re-tighten them at every stop. At one of the stops an old mechanic (a WW1 era mechanic) came out with the grease. Same reaction some of you are having “OMG the grease will cause them to loosen”. The lugnuts never loosened again. The thread ramp is at a self-locking angle, lubricate or not. The higher danger (the main factor) to a loosening joint is not enough tension (preload). (note that Bickford has a whole chapter just on "Self-Loosening". ) But this also tells us that this same “discussion” was occurring 60 years ago.: )

Some History: although threading has been in use ~500 years, it is only been since ~ ww2 where they started rolling threads (better bolts and faster production) and thus really started being more common. The civil engineers were still using rivets into the 1950’s. Understanding Bolted Joints is a whole other issue, and is relatively new, considering mechanical engineering is a relatively new profession (only ~ 120 years old). Even now it is only touched on in engineering school, so probably 99% of engineers won’t know any more than a good mechanic. Like anything, the people that do understand are those that spend some time on it.

What’s been established / convention is not going to change; I know there is no way vehicle OEMs will start saying use grease or oil on your lugnuts. Hard chrome anti-gall coatings (as I see on my Highlander) that provide a consistent nut factor (~friction), are of course good, and thus to a degree make this discussion a moot point.

We can see that the common understanding, just based on the comments in this forum, is lugnut lubrication is bad. (And trying to convince otherwise is probably not going to happen : ) Where did this come from? Perhaps with the use of the rattle gun (with actual torque being way too high), maybe the speed and hammering (when dry) creates a ramping high friction and thus can get away with it, versus lubed: it just keeps turning. Rather than fix the issue (in-accurate torque), the “wisdom” that was passed down was to not use grease? Or more simply, grease is slippery so logically it's the culprit for loose nuts?

Perhaps a reason the OEM’s continue to provide dry torque values (or just “torque value” with no mention of dry or lubed), is that if lubricated, it’s still safe (or safer imho). But the opposite would be a disaster: Lubricated torque values, but a “dry” lugnut: that would be a guarantee for low preload.

By the way, when you regularly check your lugnuts and if they are often loose: 1) Stud tension is too low for the load. Get it with higher torque or less friction(lube) but get it you must. 2) Aluminum. Probably deforming / yielding (under the nut or washer face) and thus you are losing preload. Doesn’t take much. Might not even be visible. Aluminum work hardens to some degree, but just like snowshoes prevent post-holing, A bigger snowshoe (the washer) is a MUST to spread out the force (even if it’s only a bit bigger, every little bit helps, since the area increases ^2). Also since aluminum (the joint) is thicker you do need to keep the elastic interaction in mind, ie, the three passes is smart, I will add an initial ~5 % pass just to make sure I don’t cock anything and also a final check pass. Once again, I do recommend a light oil or protectant spray if nothing else. But maybe not if a rattle gun (extreme high torque 2x+ over recommended !) is going to be used. I guess the bottom line is to check them regularly especially when new or if any component is new, while embedment is occurring.

[Iowa Dave]

Thanks for your research and taking the time to report. Very Thorough
Iowa Dave

[HABBERDABBER]

I will read & re-read your post in detail. I have no opinion right now on the matter.


But what I do know is that a little bit of lubrication can make all the difference in devices and nuts & bolt things.



How that impacts lug nuts, ....I don't know.


But thanks for posting this info.

[WillyB]

I’ve been following this thread for awhile and maybe I’m just completely confused.

Is there something inherently different about aluminum rims on a travel trailer/Escape Trailers versus aluminum rims on cars and trucks?

I’ve driven multiple cars and trucks a few hundred thousand miles and have never had a wheel fall off. Including the ones I’ve put on with a 4 way in my garage un-torqued by a 157 lb skinny guy.

Can somebody explain the concerns and differences?

Thanks!

[HABBERDABBER]

I agree, I've not had a wheel roll off. But this is a fundamental notion of no lube vs lube, and possibly an ageless myth of no lube has been the response, and it may not be correct.


I dunno.


Got to read up.

[Mike G]

My son is a mechanical engineer, so I asked him what he knew about this. He said it's actually true that lubricating the studs will result in a far more consistent tension. But there are problems.


A very slippery lubricant in particular can cause over-tightening. One would need to know how slick the lube is, then reduce the torque by a certain factor to compensate. There are ways to calculate this based on the rating of a given lubricant, but one would have to know that rating and do the math to compensate.


My son wrote:
So, if lubrication is better, why don’t the automotive companies specify it that way? Because there is more room for people to screw it up in real life application. If someone has to change a tire in the middle of nowhere, they probably don’t have a fresh batch of lubricant with them. Or, they would forget to apply it. They could apply it incorrectly, such as only putting it on the threads and leave the nut face dry. The wrong kind of lubricant could be used. Who might be held liable for a screw up? So, they go with the KISS method and settle for inconsistent stud tension in exchange for simplicity. Proper use of lubrication with fasteners is definitely a good thing, but it is also not necessarily a good idea for mass public consumption.


My conclusion: lubricating fasteners is not for the laypeople; it's best reserved for those who are trained to work with that sort of thing all the time (the engineer types).

[Brian B-P]

Originally Posted by WillyB

Is there something inherently different about aluminum rims on a travel trailer/Escape Trailers versus aluminum rims on cars and trucks?

I’ve driven multiple cars and trucks a few hundred thousand miles and have never had a wheel fall off. Including the ones I’ve put on with a 4 way in my garage un-torqued by a 157 lb skinny guy.

Can somebody explain the concerns and differences?

Yes, but the difference is the vehicle, not the material. Modern cars and trucks have hub-centric wheels, so the wheel is always properly centred on the hub and it's not difficult to get it rotated to the right position so that the nuts seat properly (although some people still manage to mess this up). Trailers still have lug-centric wheels so the cone seat nuts can be tightened with the wheel slightly off-centre (so the nuts are not fully seated into the wheel); as soon as the wheel rolls under load it moves a bit and loosens up. If the slight thermal expansion difference of aluminum alloy makes the problem a bit worse the aluminum wheel will be blamed, but in fact most car and truck wheels are aluminum (with cone seat nuts) and loosening is not an issue with even moderately competent installation.

[Iowa Dave]

Originally Posted by Mike G

My son is a mechanical engineer, so I asked him what he knew about this. He said it's actually true that lubricating the studs will result in a far more consistent tension. But there are problems.


A very slippery lubricant in particular can cause over-tightening. One would need to know how slick the lube is, then reduce the torque by a certain factor to compensate. There are ways to calculate this based on the rating of a given lubricant, but one would have to know that rating and do the math to compensate.


My son wrote:
So, if lubrication is better, why don’t the automotive companies specify it that way? Because there is more room for people to screw it up in real life application. If someone has to change a tire in the middle of nowhere, they probably don’t have a fresh batch of lubricant with them. Or, they would forget to apply it. They could apply it incorrectly, such as only putting it on the threads and leave the nut face dry. The wrong kind of lubricant could be used. Who might be held liable for a screw up? So, they go with the KISS method and settle for inconsistent stud tension in exchange for simplicity. Proper use of lubrication with fasteners is definitely a good thing, but it is also not necessarily a good idea for mass public consumption.


My conclusion: lubricating fasteners is not for the laypeople; it's best reserved for those who are trained to work with that sort of thing all the time (the engineer types).

Thank your son for his straight ahead, easy to understand explanation. As I posted earlier I am not a lubricate the threads person and doubt very highly that I will change now or in the future. Which by the way, is in the hands of our sons and daughters.
Iowa Dave

[WillyB]

Originally Posted by Brian B-P

Yes, but the difference is the vehicle, not the material. Modern cars and trucks have hub-centric wheels, so the wheel is always properly centred on the hub and it's not difficult to get it rotated to the right position so that the nuts seat properly (although some people still manage to mess this up). Trailers still have lug-centric wheels so the cone seat nuts can be tightened with the wheel slightly off-centre (so the nuts are not fully seated into the wheel); as soon as the wheel rolls under load it moves a bit and loosens up. If the slight thermal expansion difference of aluminum alloy makes the problem a bit worse the aluminum wheel will be blamed, but in fact most car and truck wheels are aluminum (with cone seat nuts) and loosening is not an issue with even moderately competent installation.

Perfect!

Thanks Brian!

[75thRanger]

I've never heard of lubing nuts and bolts but I've never heard of many things. It appears it has been done both ways with no problems.

I have never read about an accident where a person had 'failed to lube his lug nuts', nor have I read about someone lubing the bolts and losing a wheel.

Seems to be an answer to a question no one has asked until now.

[T&J]

Originally Posted by Centex

IMO you make the mistake of failing to recognize that the underlying and ultimately critical objective of a fastener torque specification is to achieve an intended design tension on the fastener itself. It is tension on the fastener that dictates the actual performance of the assembly (along with friction of all of the assembly interfaces in consideration of certain loading conditions such as shear).

Fastener torque, when measured under proper conditions (i.e. CLEAN AND DRY unless otherwise specifically directed), is a good and well-established surrogate (proxy indicator) for the actual tension imposed on the fastener; a surrogate that's useful and necessary in the actual practice of assembling components because there is no practical tool for directly measuring actual fastener tension in the real-world setting of component assembly (though measurement of fastener tension is certainly practical in the laboratory setting).

For any given torque-wrench reading (the value of the surrogate) the actual tension imposed on the fastener will differ between lubricated and dry conditions. It is in that critically important sense that the torque value can be rendered "false" - that is to say that the torque value expressed on the measurement device (the torque wrench) is no longer a "true" ("valid", if you prefer) surrogate expression for the tension imposed on the fastener. Again, it is the actual tension on the fastener that dictates the stresses on the assembly, on the fastener itself, and thereby the actual performance of the assembly.

The long and well-established standard for fastener torque specifications is based on CLEAN AND DRY fasteners (unless specifically and explicitly stated otherwise); that's the condition that yields the intended fastener tension, the the underlying critical performance factor for the assembly. The surrogate is not 'perfect', but the imperfect correlation between a properly measured fastener torque value and the actual tension imposed on the fastener of interest is well-established and considered in the derivation of those fastener torque specifications.

So yes, it may be more accurate to say that lubricating a fastener can yield "over-tensioning of the fastener" rather than saying it yields "over-torqueing" as expressed on the torque-wrench. But regardless of the semantics the point is that lubrication (or anything other than CLEAN AND DRY) can lead to imposing stresses on the assembly that it is not intended to manage and failure of the assembly to perform as intended. And those are potentially property and life-endangering conditions when it comes to road-wheels.

Well said. I believe you have it exactly right.

[75thRanger]

To lube or not to lube? Got me worried sick! ) Probably won't do anything different.

[Greg A]

Agreed, very confusing.
One thing is for sure though, I am not lubricating my nuts...

[Ron in BC]

Originally Posted by 75thRanger

To lube or not to lube? Got me worried sick! ) Probably won't do anything different.

At least I don't have to be worried sick about oiling the lead screw on my ancient wood vise. They're pretty clear about that. I guess they discovered pretty early on that an oiled screw would let someone put too much force on the handle and snap the casting.

Ron

[Hawkeye Ed]

Now that I've read all this and am ready to check the torque on my 5.0's lug nuts:

What's the best way of getting those darn while plastic hubs off the white painted wheels?

I've resorted to kicking them off because twisting a screwdriver in the little side slot scratches the paint. But that's not very elegant and besides leaves black shoe scuff marks on the hubs.

[Ron in BC]

Originally Posted by Hawkeye Ed

I've resorted to kicking them off

By far the simplest way to get them off is to have a small pry bar, similar to a brake adjusting tool. Narrow enough to fit in the recess that you've been putting the screwdriver in.

You could also make one by taking a cheap screwdriver and bending a 90* turn in it about a 1/2" to an inch from the end. Definitely twisting a screwdriver is the kiss of death for the paint.

Ron

[Tom&Joan]

Originally Posted by Ron in BC

At least I don't have to be worried sick about oiling the lead screw on my ancient wood vise. They're pretty clear about that. I guess they discovered pretty early on that an oiled screw would let someone put too much force on the handle and snap the casting.

Ron

I had to check to make sure I still had my wood vise! Yup, It is identical to Ron's. I had to take it apart once to see how the ingenious design worked. Very clever.

[Tom&Joan]

If only I were as articulate as Mike G and Centex. Spot on guys, just plain good logic.
Tom

[Rossue]

Called CHP near the accident to ask what the cause of the tire coming off and killing someone was. Did the tire come off after all the lug nuts did too- or was the tire still attached to the hub/drum. They won't say- only "interested parties will know". To me that is wrong; there should be public awareness to this, especially now with the large number of pandemic newbies out there towing trailers.

[Iowa Dave]

Originally Posted by Greg A

Agreed, very confusing.
One thing is for sure though, I am not lubricating my nuts...

In hot weather with new blue jeans there can be a problem with galling. And commando
Is definitely not an option.
Iowa Dave