FWIW: Spurred by comments on this site and warnings in my owner's manual I purchased a torque wrench just for my lug nuts. It turns out that my version of "goodntight" was way over torqued. I don't think it will have any effect over time, but it made me feel better.

 

There is a range of acceptable torque for lug nuts. It is rather wide.

Personally, I never measure torque and just do a foot bounce test with a wrench. Am I wrong?

 

I use a torque wrench on my aluminum wheels which are a little more "delicate" than steel wheels.

 

92 ft-lbs (or lbs-ft if you prefer), in case anyone is wondering.

 

I think the usual way is "tighten it till it snaps, then back it off half a turn".

 

Been there, done that. lol

 

Seriously though

The point of using a torque wrench on lug nuts is to prevent UNEVEN tightening, which COULD result in vibration under braking (because the rotors are not true).

I use 'goodntight' for most things (except engine assembly). Or, two grunts and a f*rt.

 

Appropriate timing... I just broke off a front stud using a 12" wrench. I was so shocked when it happened it actually triggered a headache. I did not cross thread the lug; I hand threaded it in place and was at the last stages of "opposite-diagonal" torquing the lug nuts, when one just kept turning. I would guess I was applying ~90-100 lb-ft (I am 170 pounds and was not bouncing or stepping on the wrench).
Then it snapped.
And you can't replace single wheel studs. You have to replace the entire wheel hub.. at $537 (plus labor). Jaguar won't cover it under warrantee, which I expected because I did it in my garage and they don't know if I was using an impact wrench on it (except for my word).

 

Just sheer (shear) bad luck I reckon, no pun intended honest yer honour, sometimes a stud will snap for no apparent reason.
You can replace single studs but you have to remove the hub to do so, this has been covered here before.

 

With an 18" ratchet, it's very easy to put far more than 92 ft-lbs on a nut by barely leaning into it. That along with the stud fatigue that can occur with loosening lug nuts partially seized by corrosion. I always use anti-seize lubricant* and an accurate torque wrench when messing with the wheels (even though I use a grunt gauge on most other applications, engine and rotating assemblies excepted).
* There is a misconception that it is thread friction that holds on the nut. It's actually thread and stud deformation that prevents the nut from coming loose. The proper torque required depends on stud diameter and material/grade/hardness (all interdependent). Over tightening on a regular basis will fatigue the stud. Under tightening will...well, you know.

 

Seeing the thread title, I thought the discussion would be about the recommended torque as there is often misunderstanding of the numbers where a low and a high number is given. However the Owner's Handbook is unequivocal - it is 92 lb.ft (125 Nm).

Also important is the tightening sequence which ensures no uneven stress is applied to the wheel.



What is not mentioned in the Owner's Handbook but appears in the Workshop Manual is application of a small amount of grease of the face of the hub and spigot to prevent the aluminium wheel binding to the steel hub as a result of exposure to rain and salt.




Graham

 

My manual also says torque them all progressively to 50lbs-ft, then on to 92lbs-ft. I guess if one lug is at 92 and the opposite one is zero, it might cause some unwanted stress.

 

Yep- all of the above... I learned how to properly torque heavy machinery components decades ago on the job. Actually wrote the procedure in a few manuals for our equipment.
I cleaned & lubed the threads, finger tighten all five lugs first, then progressively tighten in an opposite-diagonal sequence, slowly increasing torque until you reach the final setting.
Although I didn't use a torque wrench, I was using a 12" wrench with one arm-strength.

 

If you lube the threads then the recommended dry torque setting will be incorrect and too high!

 

Initial torque specifications assume that there is still cutting oil on the threads. Torquing a dry or corroded nut will result in too little loading on the stud, allowing the nut to loosen during operation. Empirically, I've been lubing the studs with never-seize for half a century (hub centrics and hub faces as well) and have never lost a lug nut or twisted off a stud. (Street vehicles, racecars, off road-vehicles)

 

So when one is torquing down the lug nuts after a wheel change after a year or so with no cutting oil present at all are you saying that one should put lube on the thread?

With all due respect I totally disagree with you as the manufacturer's specs are not for initial factory fitting but on the road use.

All articles that are engineering based support what I have stated.With Steel wheels maybe no problem with Aluminum absolutely.

This quote by an engineer sums it up quite well:

"Do exactly what the manufacturer of the vehicle states in service information. Why do I say this? The nut rotational friction and bolt clamping force are both affected by the choice of lubricant used or lack thereof. Almost all OEM's specify no lube. This is done for several reasons. Dry results in the most thread rotational friction, a most desirable attribute, this significantly reduces the chances of the lugs backing off and the wheel coming off.

The biggest concern is a wheel coming off at high speed. This is a highly dangerous event because the wheel accelerates ahead of the vehicle as it comes off at great speed and can and has caused deaths.

Of slightly less importance, but still relevant, is that lubricated threads create a higher clamping force for a given torque than specified. This can stretch the studs or bolts, warp the hub flange and/or brake rotor."

 

I started using WD40 as a way to clean and mildly lube lugs years ago after I had a difficult time with some rusty lug nuts. Until this, I never had an issue. After reading these different opinions, and researching the topic, most say that the stress on the stud can be much higher with lubricated threads (makes sense). Most common recommendation I read was to make sure the threads are clean, but not greased.
This may be why I broke the stud... ? Maybe, maybe not... regardless I plan on cleaning but no WD40 on future applications.