Those hard to undo wheel nuts!

[Tony LEE]

"no worries, lube em up"

Hard to argue against technical advice given by a bloke that fits tyres.

[engineer]

Hard to argue against technical advice given by a bloke that fits tyres.

What's that supposed to mean?
They do more wheel nuts than I'll ever see in my life, I believe they have a good amount of knowledge to contribute.

[Tony LEE]

What's that supposed to mean?
They do more wheel nuts than I'll ever see in my life, I believe they have a good amount of knowledge to contribute.

At least you figured out that it was dripping with sarcasm.

I eat lots of peanuts but that doesn't mean I know the slightest thing about their nutritional value, health implications or how to grow or market them. I'm good at eating them though.

It means exactly what it implies - that a tyre changer is not the best person to rely on for advice on engineering aspects of the relationship between lubrication, nut torque and bolt strain. It also means that someone who has a mate who is a tyre changer is more than a little irresponsible in passing on such misinformation as if it were accepted procedure.

My experience of tyre changers leads me to believe that unless you stand over them and direct that part of the operation, most of them will grab a rattle gun, spin the nuts up in any sequence that is convenient and declare the job done. If the tightening operation involved any sort of impacts then it is just not possible to rely on any rattle gun setting to give you accurate torques.
If you insist and they do figure out where the boss keeps the torque wrench, they spin the nuts up as above, grab the torque wrench, grunt with satisfaction as they hear the click and declare the job done. The "I told you so" smirk covers up that they are completely oblivious to the fact that unless the nut moves with the torque wrench, the nut was too tight to start with.
Too bad if the driver hasn't got two or three metres of pipe to slip over the handle to get them undone out on the road somewhere.

Hence the title of this topic "Those hard to undo wheel nuts!". I know the problems. My bigrig specifies 550ft-lbs and the last thing I need is a couple of hundred extra ft-lbs chucked in for good measure.

[engineer]

just for the record, my tyre fitter does my wheel nuts up with one of the most expensive torque wrenches money could buy. He wont even let me use it!!
I feel sorry for you that you have such a low opinion of such people.

[michaelgroves]

The problem with using any form of lubrication on any part of the nut (thread or face) is that using the recommended torque to tighten them must result in greatly increased stretch of the stud and this makes them more likely to break.

You're technically correct. However, I suspect there's not greatly increased stretch, and nor does it make the stud much more likely to break. General experience seems to be that studs breaking is not a real-world consequence of lubricating wheel-nut threads and faces, (even when some idiot also then uses a rattle gun to tighten them). But nuts seizing is a very real and common problem.

So, lubricate and tighten to the correct torque seems to be the best overall advice.

(I wouldn't worry about the accident investigator story too much. I can't see the presence of lubrication being useful prosecution evidence. The useful and obvious evidence is that the wheel came off! It wasn't torqued up correctly. What does a trace of lubrication add?)

[ntsqd]

If y'all want to play around with what the different K values do to the torque here is a place to start, click on "torque" and enter the pertinent info:
http://www.riverhawk.com/boltloading.php (NOTE: The bolt/stud diameter is entered in Meters, not millimeters.)

As an example I chose a 16mm stud torqued to 135 N-m and then entered the two extremes in K value. A 0.27 value resulted in a 31,250 N bolt load. A 0.1 value resulted in a 84,375 N bolt loading. That is a rather large difference in loading. Granted, I did use the extremes available (raw steel on steel vs. the slipperiest lubrication) but the point is that the type of lubrication can make a large difference in the stress in the bolt or stud.

Note that the high value is slightly above 95% of an 8.8 rated bolt or stud. My own references generally recommend only 75% of yield be the maximum torque.

[michaelgroves]

Interesting little calculator!

If it's coming that close, I'd have expected to hear of many stud breakages though, especially from those like me who lubricate their threads and mating surfaces. And I'd have thought many workshops would put way more than 135Nm of torque on an M16 lugnut, using their windy guns (though many recommended specs are probably a bit below 135Nm).

Then again, many wheel studs are 10.9 grade (my Land Rover ones certainly are, and so are the ones on my trailer).

It's interesting, though, that the slipperiness makes that much difference. I'll certainly be more careful not to over-tighten oiled wheel-nuts in future, even though I still think lubrication is a good trade-off.

[kerry]

I think lubrication is a reasonable course of action because it is much easier to check and tighten a loose lug nut that 'might' occur from lubrication than it is to try to break loose a lug nut that is frozen.

[Bandicoot]

In terms of simple cheap indicators that show if a wheel nut is coming loose, I see this type on mining equipment (including light vehicles) all the time on mine sites. See http://www.cpsafety.com.au/ but there are probably others that make similar plastic caps that are just as effective.
Bandicoot

[ozzyfishaman]

Ya know guy,s we worry about the extra torque load we are applying to the wheel studs when we tension the nuts up with anti-seize,What do think happens when you have to apply a 6' long socket bar or a huge rattle gun to the stud when you apply them to undo a seized nut !!