So after some reading on this and other forums, it seems that a lot of people have an issue breaking or stretching lug studs with the recommended ft lb. I had the pleasure of dealing with this myself today, 13 times. Yes, 13 times. Discount Tire broke a lug on my truck yesterday, so they paid for a shop to replace it. Little did the shop know what they were in for. Long story short, I am fairly certain that we have found a very plausible scenario for these broken lugs. Toyota uses a lugnut with a permanent washer in place. If any oils, road grime, etc get into the space between the lugnut and this washer it makes it act as a bearing. When this happens, the tq wrench now will not see the 83ft lb when it is reaches it. Instead, this "bearing" will allow the lug to continue to spin without ever hitting the desired tq, thus causing the bolt to be stretched and/or broken. Be sure to spray some brake cleaner or something on your lugnuts if you are using anything other than german tq (gooodentyte).

I don't thing that contamination can affect the torque. The torque reading is neither based on friction between the bolt, nut or wheel nor the length of the bolt. the wrench will reach a certain torque it would click.

It didn't, and it does. Trust me, I dealt with this for almost five hours. Cleaned the lugnut in question and clicked on the first try. Skeptical, sure, but believe me.

In the other thread about this there was more info that I see I did not post here. In my situation when we put the lugnut on without a wheel on and tightened it down it torqued to 83ft lb without an issue, put the wheel back on and on the dirty lugnut stretched the stud immediately. Seems stupid, I know, but doesn't make it any less true.

I think brockeverly is correct here. I'm not 1engineer- but to say torque isn't based on friction between the wheel/nut/stud relationship is just plain silly. It takes friction to allow the torque to occur in the first place, right?

Errr- just hold on a minute until he shows to 'xplain everything. Ooooh- 1engineer! Bail me out here...

Take a bolt, oil its threads and try to torque it; it will be torqued to almost the same number of turned as non-oiled bolt.

Good point- however, take the same setup that's rusted and corroded and torque it. How will the extra friction effect the torque? It will give a false reading most certainly.

A properly calibrated torque wrench will always show the correct value, regardless of the bolt condition.
If the bolt is very rusted and corroded, there may be a case that it get stuck prematurely and the torque value will be reached when the bolt is not all the way in.
Friction will somewhat affect the point where the torque is achieved, but to break a lug that designed to withstand 83 ft-lb you have to exceed this value.

What you are saying makes sense...but

I think brockeverly's OP makes sense too. I'll wait till the experts chime in.

Lubrication, and conversley, grit, most certainly affect torque on a bolted joint. Adding lubrication when it's not specified can reduce torque between 15 & 25%. This isn't speculation; it's an accepted engineering rule of thumb.

A capscrew/nut combination, or stud/nut combination is designed to be stretched. Lubricating a fastener that is designed to be dry could over-tighten it. This can damage the threads or over-stretch the capscrew or stud past its elastic limit. If you do, you weaken the fastener system appreciably.

In other words, lubricating = easier turning = more bolt stretch before torque wrench "feels" it, and clicks or shows on an indicator.

It happened to me too the tire shop said they see it alot on Toyotas the reason they gave me was that they use a size 12 lug when it should be a size 14 or something like that. It sounds like a load of bull to me, but if I had the extra money just laying around I would switch them out anyway, can't go wrong with a stronger part.

Torque, when dealing with bolts and nuts, is a very simple formula that can get complicated real fast.

T = K × D × F

where T = torque, K = nut factor, sometimes called the friction factor, D = bolt diameter, and F = bolt tension generated during tightening. This formula is often called the short-form equation and you don't really want to see the long form expression.

Let me explain a few parts of this equation and the parts you folks are discussing:

T= Torque, which is sort of a way of measuring "clamp force" when dealing with your wheel studs. Other ways are used but I will leave those alone.

K= Nut or Friction factor....or in my world the CYA or fudge factor. Very important multiplier that can change for different applications and usually only determined by actual testing. In the situation you described it gets complicated. Here are some of the variables that could change the "K" factor in the equation: Is the bolt plated? Is the plating zinc? Is the bolt lubricated? If so, what type? What is the bolt's temperature? Has the bolt been pre loaded before? If so how many times and was the preload correct? And on...

D= Bolt Diameter

F= Bolt tension. The bolt tension is caused tightening. The bolt is stretched a bit during tightening. In some cases the thread can be deformed which you guys know as "stripping".

Bottom line: Can lug nut torque be changed by lubrication? You bet. How much? I have not a clue, sorry. Wiskey Wizard states a percentage and while that may be true in some applications I don't know if it applies here because:
A) Even though you have multiple lug nuts they act as one unit. The K factor will change depending on if all bolts are lubricated or only one, or two, etc.
B) Type of lubricant makes a huge difference. Don't say "It was oil" 'cause that won't help haha.
C) What was the temperature? Makes a big difference too.
D) How many times have they been torqued and were they torqued properly before?

All in all, it is a good idea to clean your bolt before torquing unless it was designed to be lubricated, which wheel studs are not. So yes, lubricating a wheel stud before torquing the lug nut could cause the stud to break because your torque values will be higher. Just don't know by how much. Hope this helps and tried to keep it simple.

Oh, Antman, your rust analogy was very good! BBB, there are some lubricants out there that will absolutely change the "real torque" vs. "measured" torque.

^^ Holy smokes, Antman, see what you've done?

Anyway, a size 14 lug nut is 2 mm bigger than the stock 12. Not certain, but they might not fit.

Well, I think that settles it then! Thanks 1engineer.

I think we are done here

I have spent hours and days debating this subject throughout the years with some of my colleagues. You really don't appreciate these formulas until you have set down with a clean sheet of paper and had to design a nut and bolt for a specific task because there was not one commercially available. Sometimes, when you need to hold stuff together that can generate 500K lbs/force you just can't go to NAPA and get it out of the bin haha!