Lug nut lubrication?

[Selden]

This is something I have wondered about for decades. Is there a received wisdom regarding use of anti-seize lubricant on threads for wheel studs/lug nuts? I changed a flat tire on my father-in-law's Olds this morning, and noticed that the studs had been lubed with what appeared to be blue marine grease. The studs on my R1100 RT are bone dry. My inclination is to put a little bit of anti-seize compound on the threads, but I want to check for other experiences/opinions on this.

 

Also, I (finally) got my rebuilt rear shock back today. Although I have looked in the service manual, I didn't find anything about whether to use Loctite on the threads for the top and bottom shock bolts. Again, is there consensus on this? No Loctive was evident when I removed the shock, but since it's an Ohlins, I have no idea if Loctite was used with the OEM shock.

[Rob L]

The threads on your bike should be assembled DRY. NO LUBE! That is what BMW says. Clean the threads with a wire brush or whatever. Assemble dry. Torque to the first setting in a cross pattern, then increase to the final torque setting and again us a cross pattern. I believe the torque settings are 30ft/lbs. and then 72 ft/lbs.

 

I know dry seems wrong, but the torque settings are for a dry thread. Lubing them would allow them to be over stressed and possibly cause a broken stud. Not a good situation

[johnlt]

Be aware that some of the shock mounting bolts or nuts are "single use" only and should be replaced after removed. You can probably get away with re-using them but BMW says "replace" them with new ones.

[Selden]

Thanks for the replies -- I figured there was a reason for dry threads on the wheel studs. The nuts on the rear shock bolts look like generic nuts, but they do have added resistance on the last turn.

[Mike05]

Selden,

 

Limecreek posted an excellent series (pictures included) about installing Ohlin's on an R1200RT back in July of '06. In it, blue loctite is used on the bottom shock nut.

 

Also, if I remember correctly, BMW does recommend replacing the top shock nut.

 

I used blue loctite on the bottoms of both front & rear Works ESA replacement shocks when I did mine.

[GordonB]

The bottom shock bolts replaced as recommended by BMW will come with a stripe of loctite on the bolt. The top nuts are 'pinched' to act as locknuts and are also recommended to be replaced. I found the nut for the top front shock a bit loose after re-use.

[Smoky]

I know wheel bolts are supposed to go on dry.

 

However I have added the tinyest amount of antisieze, they stay tight, and remove smoothly.

[Joe Frickin' Friday]

This is something I have wondered about for decades. Is there a received wisdom regarding use of anti-seize lubricant on threads for wheel studs/lug nuts?

 

The wisdom is received from the Holy Handbook of BMW, i.e. the owner's manual. If the manual doesn't specify lubed or dry, then you can safely insert your own judgment. But in this case, I believe the spec is dry.

 

The issue has of course been beaten to death here in the past. Here's something I wrote about 3 years ago:

 

Here is a pretty basic formula that relates applied torque, bolt diameter, and bolt tension/preload:

 

T = K * F * d

 

Where

T = applied torque (the torque spec)

K = torque coefficient

F = bolt tension (preload)

d = bolt diameter

 

Just make sure you get your torque and diameter in compatible units. IOW, either the torque is expressed in N*mm and the bolt diameter in mm, or torque in N*m and bolt diameter in m.

 

The torque coefficient, K, accounts for thread surface condition, geometry, pitch, and lubrication. The math is pretty ugly, but the fact is that because of friction, thread pitch differences don't matter much until you get to ludicrous thread pitch angles; IOW, where torque vs. preload is concerned, UNC or UNF really doesn't matter.

 

But lubrication does. Here's a table, from Shigley & Mischke's "Mechanical Engineering Design:"

 

Nonplated, black finish: K = 0.30

Zinc-plated: K = 0.20

Lubricated: K = 0.18

Cadmium-plated: K = 0.16

Anti-seize: K = 0.12

 

As you can see, the torque coefficient can vary widely with conditions. Heck, just replace your original black-finish bolt with cad-plated, and you could nearly double the bolt tension for a given torque. Likewise with going from zinc-plated to slathered with anti-seize. "Lubricated" is pretty ill-defined; it's not clear whether they're talking about WD-40, sewing machine oil, or bearing grease. And that's the problem: you just don't know what kind of K-factor you're getting when you deviate from what the manual says.

 

As Ed points out, excessive preload may plasticly distort the bolt, in which case you're not even getting the expected preload. OTOH, the bolt may take it without a problem, but you just don't know unless you know what the bolt grade/class is, and have crunched the numbers. And even if the bolt can take it, the over-spec preload may distort sealing surfaces or damage parts. One guy may get away with it ("been using lubed bolts for XXX miles now"), but may be within a hair's breadth of catastrophic failure and not know it; the next guy may use a more slippery lube or torque it a smidge tighter, or hit a slightly bigger bump, and have his overstressed wheel hub crack to pieces at 80 MPH.

 

Bottom line: if you haven't done preload-versus-torque testing for the thread conditions you're working with, then it's a shot in the dark. BMW has determined the optimum preload and the thread/torque conditions that are most likely to get you close to it; if you deviate from those conditions, you're not likely to hit the desired preload. I'm not saying you will crash/burn/die, but you definitely are adding an unknown factor into things.

 

If you have a concern about excessive corrosion, I'd recommend simply buying new bolts.

 

Additional material:

 

Loctite has some K-factors for their products, here on page 5. Depending on which of their products you choose, the K-factor varies from 0.11 to 0.18. They don't offer a representative K-factor for dry threads.

 

Another list of K-factors here, ranging from 0.12 to 0.35, the latter for dirty/rusty threads. This brings up an interesting point: there's no indication that the manual's torque spec was not chosen with slightly rusted (but dry) threads in mind. No one has shown me a compelling reason why I should deviate from what the original design engineer has spec'd for these bolts. Can't loosen the bolts a couple of months later? That's what breaker bars are for. Riding on salt-crusted roads in mid-February? Wash your bike with cold water when you get home, just like the owner's manual says.

 

 

Those of you who don't believe in lubricating fasteners are increasing chance of failure, in my opinion.

 

If the design engineer gives a torque spec and indicates that the spec is for lubed threads, then yes you should lube it, and you're likely to underload the fastener if you don't lube it.

 

If, OTOH, the design engineer gives a torque spec and indicates that the spec is for dry threads, then you're most likely to load the fastener correctly if you don't lube it.

 

Yes, joints loaded beyond spec may or may not fail, but I'm not sure why you'd think that following the directions (the manual is pretty explicit about providing several "CAUTION" bullets in the procedure regarding not lubing the threads) would give unsatisfactory results.

[mbelectric]

OK, now that we know EVERYTHING there is to know about lug nuts and the scientific and mechanical application thereof,

 

may we get back to a decent oil thread now???

 

 

MB>

 

 

[Selden]

Good god, Mitch -- as my daughter used to say when she was a teenager: TMI, although I think you managed to avoid making a recommendation. I cleaned the threads with brake parts cleaner, and tightened to feel, as I usually do, based on the feel when I used a torque wrench. I mean, realistically, if you have to pull a wheel on the road, how many people travel with a torque wrench? In 46 years of riding and wrenching, I think I have a pretty good feel for how tight things should be in this situation. I have a big gripe with most tire shops, which almost always over torque lug nuts on alloy wheels. I'm a little more anal when it comes to torquing cylinder head bolts, and use a torque wrench there.

[Paul Mihalka]

On my previous bikes I did it like you, Selden, by feel, and never had a problem. On the R1200 I use a torque wrench because the bolts are much smaller and use less torque. If I'd do it by feel I would over-torque.

[T__]

Selden, obviously BMW has it’s own reasons for not lubricating the threads on the wheel bolts..

 

The motor company I work for had a rash of wheels coming loose back in the late 80’s & we really couldn’t figure out why as none of our test vehicles had any wheel loosening issues.. We tried to capture some customer vehicles that had loose wheel issues but by the time we captured the vehicles the damage was already done,, or repaired in the field.. Most if not all the problem vehicles had aluminum wheels so that was the focus at first..

 

Seeing as we couldn’t find any valid customer vehicles that were (pre) loose wheel we decided to do some testing to see if we could duplicate the customer in-field problems..

 

Our first try was just lightly greasing the wheel studs then running heavy acceleration & braking coupled to high G lateral forces.. Nothing really showed up with that test so we moved on to greasing the lug nut taper to wheel taper interface.. That showed some promise as the wheel lug nuts were regressing (sinking) into the tapered aluminum seats enough to allow retention torque loss.. Still it took a lot of harsh treatment to get a wheel to come loose.. Then we tried greasing the tapered lug nut & wheel seats as well as greasing the interface between the wheel & the brake drum or brake rotor (depending on vehicle brakes).. That was the key as we just couldn’t keep those wheels tight as they would work on the hub as well as work the nuts deeper into the aluminum wheels & a loose wheel resulted..

 

We (think) what was happening was that tire shops & repair facilities were slopping some grease on the wheel studs & wheel pilot where the wheel seated on the hub & it migrated up between the wheel & rotor or brake drum from heat & was pushed into the nut taper a the nut was run down the threads..

 

We turned the data over to our legal & warranty department so I’m not sure if letters were sent out or not.. My engineering team only identified the problem so didn’t so a field failure follow up..

 

 

Twisty

 

[Selden]

We (think) what was happening was that tire shops & repair facilities were slopping some grease on the wheel studs & wheel pilot where the wheel seated on the hub & it migrated up between the wheel & rotor or brake drum from heat & was pushed into the nut taper a the nut was run down the threads.

As always, very good information. I think tire shops is the explanation for the blue grease on the studs of my father-in-law's car. Yet another reason why I like doing my own maintenance whenever possible.

[Peter Parts]

Interesting to read Mitch's in-depth tech piece. Seems there is no inherent advantage to grease vs no-grease.

 

Interesting to read Twisty1's piece although I struggle to apply his nicely researched findings to my bike wheels.

 

This is strictly a minority opinion and one based on my experience in human-factors... which is a crucial aspect of systems performance often ignorned:

 

1. You should aim for the right tightness - whether grease or no-grease or converting when a manufacturer says the opposite.

 

2. In many respects, makes more sense to use grease on the filthy wheel lugs and to check your wheels from time to time (duh). I think of lot of us have gone from being fans of Loctite to anti-sieze fans (esp. after becoming BMW boxer riders).

 

BTW, it isn't apples-to-oranges to compare your quantity grief in removing rusted-on wheels (every few thousand miles and sometimes during a rain storm) with your quantity of grief in having a wheel come loose (profoundly rare and if you check once in a while, never). And tasks which are a PIA tend to treated off-handedly and over time, not done "by the book" properly.

 

 

[Joe Frickin' Friday]

...although I think you managed to avoid making a recommendation.

 

My unspoken recommendation on the lube issue was to do whatever the manual says; if the manual doesn't spec one way or the other, it's not critical, and you can do whichever suits you.

 

Missed the shock issue. My recollection on my 1100RT was that the shock mount nuts were upset nuts that provided their own locking friction; no Loctite required. If you've replaced these nuts with something else, then all bets are off.

[Joe Frickin' Friday]

Interesting to read Mitch's in-depth tech piece. Seems there is no inherent advantage to grease vs no-grease.

 

As Twisty's anecdote suggests, it may be that BMW doesn't want to take the chance that someone will overlube the bolts and end up slicking the wheel/hub interface, which could result in a wheel coming loose over time.

 

In some circumstances the lubing of threads is unavoidable, and is accounted for by the engineers who wrote the torque specs in the manual. Installing a cylinder head is a good example.

[Peter Parts]

Interesting to read Mitch's in-depth tech piece. Seems there is no inherent advantage to grease vs no-grease.

 

As Twisty's anecdote suggests, it may be that BMW doesn't want to take the chance that someone will overlube the bolts and end up slicking the wheel/hub interface, which could result in a wheel coming loose over time.

 

In some circumstances the lubing of threads is unavoidable, and is accounted for by the engineers who wrote the torque specs in the manual. Installing a cylinder head is a good example.

 

Ah... getting closer to a basic truth. To make a long story shorter, no way to ensure threads (esp. in heads, as you point out) are grease-free. So, in light of this human truth obvious to all except BMW engineers, best to simply grease 'em all and go from there.

 

Another "truth," relates to readers of this forum. There are cases where BMW (and other engineers) design in order to prevent real stupid people from doing real stupid things (as per your first paragraph and Twisty1's concept). Often that's wise and I do it myself... if better solutions are hard to achieve.

 

But if you and typical readers of this forum check say, at least 3 out of 4 wheel lugs from time to time, that design logic isn't applicable and other factors (such as your ability to remove your rear wheel at night in a rainstorm in the woods) becomes more important.

 

For sure one "truth" repeated in this thread isn't always true: "The Factory knows best."

 

Footnote: at my website, see below, is a related POV for not using the angle torque method on the heads.

[Peter Parts]

About loose rear lug nuts, there is another very important design feature. Unless you ride around drunk all the time, you really ought to be able to feel when the wheel is getting loose long before it falls off. Also true of cars but not our Paralever rear wheels, you can easily eyeball a stud nut that is coming undone.

 

Can't say as I know this from personal experience, but that is my guess.

 

Good engineering recognizes there are humans in the system with their strengths and failings.

[T__]

From the BMW service manual.. BMW engineering obviously had a reason to go to all the trouble of including this in the service manual..

 

 

Twisty

[Peter Parts]

Where did you buy a manual with red underlining?

[tallman]

Twisty.

Is that synthetic marker by any chance?

I switched to synthetic at 10,000 posts.

[tomk99r11]

Lube away Peter.

[Haynes]

I'm a luber. This is partly because the 1150 had some problems with rusting studs and I also find removal easier with a trace of anti-seize.

If removal is easier then I expect the risk of them coming loose is slightly higher. I live dangerously.

[EddyQ]

Unless you ride around drunk all the time, you really ought to be able to feel when the wheel is getting loose long before it falls off.

 

Peter, I have no experience with a lug nut coming loose on my BMW. But, many years ago, I forgot to tighten all the lug nuts on one rear wheel of VW car after a tire rotation. I drove 200ft down the street and stopped immediately due to the noise that reminded me of my blunder. My speed was likely 25mph or slower max. It was frightening how far all the nuts were back out with that very short distance. One nut had maybe one revolution left! Now, lubes vs dry, with all torqued on a motorcycle would likely be much different situation. One will likely loosen first, followed my some movement that likely will quickly loosen the rest. But I'm just speculating. But it may be possible to get very little warning. Especially if zooming down a highway. I wouldn't want that kind of failure. Just sayin . .