Well, it’s been more then 24hrs and no comebacks in Scott’s excellent thread. I’m posting a new thread to not go too sideways in his, but this is a subject I can’t see getting much traction ‘cause it’s so easy to get lost in the weeds.


It’s been more then 24 hours so I don’t remember all I wrote in the deleted post. Something about inconsistency in bolt tension when using nut torque for the guidance, issues with gaskets and that my head goes numb when I ask my former director and good friend about things like bolt tension. He’s a mechanical engineer with a masters from MIT. It all becomes a very deep rabbit hole because all the published data is based on assumptions.

But the real issue is friction, my career. Friction of the ramps we know as threads, the machine quality of the threads, the lubrication method and how that particular lubricant actually performs under the intense pressures bolted (nutted is the term), and the most critical, the bearing surface under the nut, bolt head, or whatever.

To show how deep the rabbit hole can be, due to the frictional forces of surfaces, in actuality if you are going to use tightening torque to achieve proper bolt stretch the torque value should be different if the head or nut is flanged or not, different surface areas. That’s not listed in most of the tables produced about torque values.

And if you want a real headache, start talking to a structural engineer who works in the field of bridge design and building. Which is why I posted the first vid where thread lubrication was shown to have such an impact. And the ways they deal with insuring those bolts are at proper tension, squirting washers.

In the automotive field bolt tension is critical in almost everything. From engines, suspension, and even electrical connections. The majority of the time everything is listed in rotational torque values, but because it is field convenient, not necessarily best practice. A better method of ensuring proper tension is a preload torque to set the baseline of non-stretch, then turning a specific amount of rotation, be it 90°, 365°, or what ever. And that’s been adapted by the auto industry for the most critical applications so the fasteners can be utilized to their maximum potential. It’s more of a headache for the person doing the work, but it’s been documented that the varying conditions of the friction forces (thread consistence and lubrication) bolt tension can vary 25-35% using rotational torque.

I’ll write more later about ARP.

 

I watched the videos in the other tread. It's one reason on many critical fasteners that I reuse I clean them on my bench grinder wire wheel as best as possible. I could probably use a lube of some sort but never been comfortable with the torque adjustments in doing that unless the spec originally calls for it.

I'm not entirely sure I am right in my thinking so this is a good thread to see what others think.

 

I think your right. In-field changes like different lubes will alter the frictional values and stretch the bolts in tension more, possibly to failure. We actually did that once in the facility.

I was going to bring it up later but ARP came out with a new lube for their head studs and had to lower the torque value. It is a lower friction formula under intense pressure and with less friction under the nut the same torque will over tension the studs.

Varying the friction of rotational force alters the clamping load, so you can get into trouble. Measuring rotational degrees or how much the stud orbit has stretched is better. But a PITA in the field. And if it's conventional head bolt, how do you measure the stretch externally?

Since I was a wheel end guy, many people believe that the warning to not lube lug nut threads was due to the possibility of loosening. Actually it was not. Lubing the threads and contact faces can over stretch the lug bolts causing either an immediate fracture within the thread root, or later down the road due to cyclic loading. The newer design like we have on our trucks, a captured bevel washer, is designed and rated for the nut frictional face to be lubed, with one drop of oil. The original torque value was 165lbft, but later in production years was reduced to 150lbft. Within the facility I developed part of our vehicle PM to replace lug nuts and studs after X amount of tests. Each test we would pull the wheels two to three times, so you could remove wheels 18 times in a month. Everyone you stretch a fastener it loses a little. Nuts more so. We extended that with the new style lug nuts as it was more controlled.

 

Took a bit to find but I remember this from years ago. If this doesn't show the importance of using the ARP lube then I don't know what will.

 

That is a good vid, Pete.

And it shows how their product with the right species eye of newt is consistent hit after hit (Hey, Halloweens coming up). And they are showing adding lubricant not only to the threads but to the contact face of the nut, or bolt.

I'd love to use it on all fasteners, but when charts give oiled torque spec's it's the Wild West unless they did like Ford in the Service manual for the lugs nuts as there is no spec for the underside of the head/nut, the highest frictional force.

I still have the bottle I put out in the shop back in '99.









And in the Ford service manual it mentions crisscross to minimize runout ..... of the rotor from stress distortion. It's no different then a crossing sequence for a head or manifold. However, unlike the manual we would the least amount of rotor distortion in stepped torque sequence. Every third lug clockwise to 60ftlbs until all complete, then 130lbft, then 165lbft. We never got the 150lbft memo.

 

I hear you. Something to think about from the video, did you see how on the 2nd torque the "peanut butter lube" went OVER spec when the same torque value was reached?
My take: The importance of the ARP lube is consistency even after 4 cycles unlike other conventional lubes. Though a conventional lube (motor oil) torque value may be all over the scale among many fasteners, the ARP delivers the even clamping force across all the fasteners so they all are sharing the load the same making the pieces more unitized.
The question to me that MAY cause concern is how a manufacture comes to the actual torque value spec? If it is based strictly on the fasteners, then I'm not concerned.
I wonder if ARP has a conversion chart of recommended torque values based on oem spec values using say, motor oil?

 

So for years I've been wrongly putting anti-seize on my wheel studs, as in any I've touched??! I was after: eliminating rust since the rusty lug nuts were harder to turn than clean ones, and getting uniform torquing.

I'll make you shake your head even more: since I swapped more wheels more times than I could ever count on the race car, and the torque was in the sub 100 lb range; I just developed a feel for how tight using my breaker bar only.

Now your brain will start to hurt from the shaking: I ONLY use a Torque wrench on lugs that need to go over 120lbs or so...

Call me a lucky guy. Dumb, but I guess lucky...
Scott

Cripes, wait until we start talking brake pads and me almost never letting a rotor get turned...

 

I always did lugs in at least two stages. On the F250s I was doing it in three stages (100, 125, 150) but since reduced it to two (100, 150). I do a crossing sequence. Never heard for a staggered sequence for lugs. It's an interesting approach. What is the science/math behind it vs the typical crossing approach that would lead to less rotor distortion?

 

I've always crossed as well. I must be reading it wrong, but it sounds like you and Jack do the same thing... (ramping up the torque in steps and cross-torquing)

 

It's not my thread but I almost wish lug nuts were never mentioned. They're just not as critical to me as long as they are ALL even. Most applications give you a window, like 90-110. That showing, to me, it is not as critical as say, head bolts.
Yes related, but not as technical as a quality fastener such as head bolts.
Just my opinion, carry on!

 

You are absolutely right -- should keep this thread cleaner as I believe Jack was just using an example and I jumped down that rabbit hole. Whereas his original intent (I'm assuming) was exactly that: critical torque and how it can vary, and because it is critical it should Not!

Fire the spokesman, Jack!

 

Good video. I remember watching it before on TV but it's still a good refresher and shows well the importance of using the proper lube.

I would assume in the case of a head stud that clamping force is the primary concern and from that a torque value specified and from that material and a fastener is designed. That's why the lube is so important in achieving the proper and consistent clamping force since that is all we (people installing the studs) really can go by is a torque value. The lube allows a repeatable torque to reach the desired clamping force.

 

Well I consider lugs pretty critical to going down the road properly. Haha! But I get your point. I would still like to hear more about the staggered sequence Jack was talking about. Mainly for my own curiosity.

 

One thing that I did not see anyone bring up was the finish of the fastener. Smooth zinc,
the ruff zinc and then onto the black oxide finish. There are a lot other types out there and
each one would have it's own rating.

Jack I think this is correct wouldn't you say?

 

May be it's me but the start of this thread I thought is for head fasteners.
Sean, I haven't seen stock bolts or ARP studs offered in any other finish.