Use of Anti Seize on Vehicle Lug Nuts

Problem is how do you know who to trust? I had new tires put on at a major brand tire shop and one was left a 45 pounds. At oil change shops they often put in the wrong pressure when checking the tires. My attitude these days is trust no one and check them yourself.

Even the good shops often have the minimum wage guys doing the tire work. How much do you really trust them?

I have also posted this question at some engineering forums and other newsgroups. The general consensus seems to be that the use of anti seize on vehicle lug nuts that are properly torqued, is not going to contribute to the lug nuts loosening. It seems wherever I posted, more people reported using anti seize on lug nuts for years without any problems, than people advised against it.

It also seems to be considered that the application of lubricants in general to properly torqued fasteners will not contribute to their loosening. It is generally considered that traverse movement is what causes fasteners to loosen

However, it probably makes good sense that the anti seize be very sparingly applied to *only* the lug stud thread and *not* the contact or interface point between the end of the lug nut and the rim. The question of whether or not to decrease the manufacturers torque specifications to account for the application of anti seize is debatable, but if you can keep the anti seize off of the contact point between the end of the lug nut where it seats in the rim, you are probably better off staying with the manufacturers specified torque. The following information will explain why.

I found some info regarding wheel stud failure here...

  The link directly below goes to a page with some interesting information regarding the difference in axial loads (preload) obtained when coating *only* the threads with anti seize, and when coating both the threads *and* under the bolt head or nut. Apparently, if the information is reliable, there is a huge change in axial load when you coat both the threads and under the bolt head or nut, as compared with hardly any change in axial load when you apply anti seize to *only* the threads and not under the bolt head or nut.

If you look at the table / charts provided near the bottom of the page at the link directly above, using anti seize on the *thread only* shows slightly less axial load than using no lubricant at all. This is probably due to the wide variation in friction of identical bolts with dry un-lubricated threads, which can be as much as +/- 25% to +/-

50%.. See the following links for more information?

(some more articles here)

They say that about 90% of the input torque of the torque wrench is consumed by friction, with 50% of the friction being between the bolt head and mounting surface, 40% of the friction being in the threads, & only 10% being the stretch of the bolt which produces the axial force or preload.

The article at mechanicsupport.com references another article titled "Failure of bolts in helicopter main rotor drive plate assembly due to improper application of lubricant" by N. Eliaz, G. Gheorghiu, H. Sheinkopf, O. Levi, G. Shemesh, A. Mordecai, H. Artzi, Published in Engineering Failure Analysis #10, pages 443-451

Here is a link to the article published in engineering failure analysis?

Regarding the article at the link directly above, it seems it was not the use of anti seize that was causing failure of the helicopter rotor bolts, but rather the improper application of anti seize that was causing failure, namely applying anti seize under the bolt head or nut instead of only applying it to the fastener threads. Applying anti seize under the bolt heads and/or nuts increased axial loads substantially. It also appears Tightening by turning the bolt instead of, as specified, the nut, resulted in more torque going into bolt tension rather than being absorbed by bolt head friction.

Would it be unreasonable to require engineers to design all *critical* threaded joints & related components (wheel lugs, helicopter rotors, etc. anything where a life may be at stake) to be able to withstand the maximum axial loads produced by torquing lubricated threads to specs with a torque wrench ? The lubricants vary, so they should design for the lube that produces the lowest friction.

It seems anti seize and/or lube on threaded joints is a good idea in most cases, plus applying the lube produces more consistent and accurate transmission of torque, so it would appear to make sense to always design for a lubricated joint.

I have also read that research has shown that not lubricating the thread and nut face will result in the friction value increasing on re- tightening which subsequently reduces the preload for a given torque value. This would be especially important regarding lug nuts, which are being removed & re-tightened frequently for tire rotations.  

It seems all torque specifications should specify both dry and lubricated threads for reference, & if lubrication or anti seize is required or recommended, it's exact application method should be specified. Although ideally the joint would be designed to withstand a worse case scenario application of lube on both the threads and under the bolt head.

At the

website, they say that it is actually transverse joint movement that causes loosening of threaded fasteners. In the case of a wheel, friction between the wheel and the hub prevent traverse movement. The friction is generated by the axial force generated by the torqued lug nuts. Because of traverse movement causing joint loosening, it's probably best to not use anti seize or any lube on the back side of the rim where it contacts the rotors, hub, or brake drums.

My feeling is the benefit of using anti seize on lug nut studs outweigh any concerns of problems it may cause. I do think it is a good idea to apply the anti seize very sparingly to the lug studs, and to try to not get any anti seize on the contact point between the end of the lug & where it seats in the rim lug recesses.

The last time I used anti seize on lug nuts, I think the way I did it was to smear a small dab of anti seize on the end of the lug stud, then run a lug nut on the stud by hand back and forth until a thin film of anti seize covers most all the stud (almost up to the rim). I ran the nut back and forth on the stud enough times so that it did not push a glob of anti seize between the end of the lug and where the lug seats in the rim when I was ready to finally tighten the lugs down. I wiped off any anti seize at the lug end as required.

If anti seize is used however, it seems wise to be extra careful to make sure that any shop you take your vehicle too only uses a hand torque wrench to tighten the lugs to the correct torque.

The main question that remains is whether to torque the lugs to manufacturers specs or reduce the torque by a percentage to compensate for any increase in axial loads due to the anti seize. Based on the information given above, & my experience, my guess is to just torque the lugs to manufacturers specs, especially if you use the anti seize very sparingly and can keep it off the end of the lug nuts where they seat with the rims.

This has worked for me and I think the fact that it did not warp my rotors is a clue that the axial loads are not too outrageous. Shops warp rotors all the time with power impact wrenches, and they might turn or replace your rotors, but they don't replace the lug studs as a precaution for the possibility of them being overstressed by the impact which warped the rotors.

This reasoning may not apply to all vehicles, especially larger tucks, but for most pickups and cars, I would think that if you have not warped the rotors and you do not feel any break pulsations, then you probably have not overstressed the lug nuts & studs to a point of any real concern. Impact wrenches break lug studs off all the time, I doubt anyone has broken a lug stud off with a hand torque wrench, whether coated with anti seize or not. I doubt any rotors have been warped with a hand torque wrench, anti seize on lug studs or not.

John

Months after a franchised Ford dealer replaced a lug on one hub, the local garage operator who put on my winter wheels reported all nuts had been torqued wrongly, worst on the wheel on which the Ford dealer had worked.

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I just removed some lugnuts from a Camry which had been subjected to a local tire shop.

Originally, this shop put new tires on the car, and kept the lugnut lock "key". When she had to return to have the tires rotated, they couldnt remove the locks and cut them off, resulting in extra expense and worry to the client.

She was worried about someone stealing the tires and brought it to me to install new locks. When I removed the necessary nuts from the four wheels, I couldn't believe it....some were so tight, it was hard for me, with a breakover bar, to get them off. Others were little more than finger tight.

I installed the new locks and cross tightened all nuts up to specs with a torque wrench.

This kind of work from a "professional" shop should be a warning to everyone.