Hi all,

Just had TPMS installed on my R99s then mouted at my local tire shop. The manager there is really nice and always gives me a great deal. But the guys in back sometimes are a little careless. So I told them to tighten the lugs to 100 lbs rather and then I'd take them to 103 at home.

That was last night. So this morning I go out to install my locking lugs and verify the torque. WOW - I could hardly remove a couple of the lugs. Had to use my knees. They say they use a torque bar and hand tighten, but they some sure seemed to be over the 103.

So my question is ... has permanent damage (well without replacing things) been done? Am I worrying frivolously? Do I now have more frequently make sure the lugs aren't loosening up?

cheers
-paul

 

most shops just hit them with an impact gun. so they will almost always be over 100. but there should be no damage done as long as you didn't snap a stud trying to get one of them loose. 90ft/lbs should be fine all the time. there is no reason to go over that. Torque properly and set the right tire pressures and you should only have to check them once a month.

 

A good reason is MINI recommends 140nm (103ftlb) for R56s.

 

90 ft-lbs is for 1 Gen MINIs with 12mm bolts. 103 ft-lbs is for 2nd Gen with 14mm bolts.

The possible damage to threads from over-tightening would be stripped threads, which would be obvious, or stretched threads. Stretched threads would make it difficult to screw the bolts in by hand. In short, if there was damage, you would notice it.

 

+- 10

 

With out a calibrated Tq wrench no one really knows what they are torquing them too. A drop from as little as 2ft can cause a torque wrench to be off by as much as 10%. This is why the aviation industry calibrates all its measurement tools. If you think a tire shop calibrates their wrenches, guess again. Even if they did most 18-20something tire jockeys could care less. Just tighten them good and tight and check once a month or so you'll be fine.

 

Sad but true. That's why my cars never sit any garage but mine.

 

A one time over tightening wont hurt anything. Another thing you may want to use is "never seize" I put a small amount on anything aluminum. It makes it so easy to remove nuts and bolts at a later date. Use it sparingly and dont get it on your interior. Its a bit hard to remove.

 

Excellent tips all around Thanks a lot everyone!

 

Anti-seize is good stuff for preventing corrosion between threads/fasteners of dissimilar materials, but since both the lug bolts and the hub they're threaded into are steel, it's not really called for here.

Also, the torque values for the lug bolts are for clean, dry threads - if you use any kind of lubricant on the threads (like anti-seize), you risk over-stretching the bolts.

 

Its good for preventing rust build up on metal parts as well. as far as it messing up the threads because of torque issues, Ive been using it for over 15 years on every car ive ever owned. never had a thread stretch from it's use. Guess it all depends on how smart the operator of the tool being used is.

 

I don't know that "smart" comes into it, since using a torque wrench is pretty idiot-proof, but if you take two identical fasteners - one lubed and one dry, and tighten them to the same wrench reading, the lubed fastener will be tighter (the fastener will be stretched more).

With lug bolts, the extra tightening is probably still within the design spec, but if you start mixing up dry and lubed torque specifications for things like cylinder head bolts, you can run into problems pretty quickly (i.e., dry-tightening a cylinder head stud that's supposed to be lubed will cause the stud to be too loose.)

 

I guess. Like Ive said, ive been using anti sieze and or loctite for many years and have never had a problem stretching nuts, bolts, or anything else on the engine, suspension, or body panels.
I guess if I looked under a microscope i may have seen a stretched part
But again, never had any issues.

 

Well, any time you tighten a fastener, you're stretching it - that's how tightening works.

Like I said before, in many cases the difference in the amount of stretch you get when lubing the fastener first versus tightening it dry isn't going to be enough to cause the fastener to fail, but it's still not a good practice to ignore manufacturer specifications. If they say that a torque spec is for a dry fastener, they're saying it for a reason. And if a torque spec doesn't specify a type of lubricant, then it's a clean/dry spec.

 

actually if you were to measure it. a lubricated part torqued the same as a dry part would probably have less actual pressure on it. sooooo i guess it isnt so bad after all

 

You will be absolutely fine. Don't worry so much on something as trivial as overtorquing wheels.

 

No - a lubed bolt will turn further and stretch more before reaching the appropriate setting on the torque wrench compared to a dry bolt, resulting in a greater clamping force between the two parts and a greater strain on the bolt.

Think of it from the other direction. If you try to tighten a rusty, cruddy bolt into dirty/gritty threads, the extra friction between the bolt and the threads will cause your torque wrench to indicate that you've reached the proper torque long before the bolt has actually stretched enough to provide adequate clamping force between the two parts.

Lubing the bolt causes the opposite result - you'll have to turn the bolt further (stretching it more) before your torque wrench will register the proper torque.

 

do either of you have a reference to a qualified proceedural reference

or are you guessing????

 

Most service manuals have a blurb in/near the front to the effect that torque specs that don't specify a lubricant are dry specs. But for general information, here's a page that lists the torque specs for various bolt diameters, thread pitches and SAE grades.

Notice that all of the "oiled" torque specs are significantly lower than the dry specs. Also, at the bottom of the page there are torque corrections to apply if the bolt is lubricated with oil, dry film or wax, or if the bolt is zinc or cadmium-plated. Depending on the type of plating or lubricant used, the baseline torque specs have to be reduced by as much as 50% to compensate for the lube/plating.

 

and to be honest with you if your off by a few lbs it would not do any harm at all. now if you were say70 ft lbs with a bolt that should be 20. youll get some stretch, but, still be able to reuse the bolt on a vehicle (different situation for aircraft).
a good example of a bolt that constantly gets over torqued is the oil pan bolt. people always crank them down yet reuse them for tens of thousands of miles.

So yes in theory youll stretch a bolt or nut from over tightening it, but again, you have to go gorilla tight to have it deemed useless.

 

Ok ok I understand the argument for exact torque specs for headbolts, rod bolts...things like that...but lug nuts? Who cares if they are lubed or not? I use anti-sieze myself because i've worked on too many older cars where getting the lug nuts off is a royal PITA and I never want that to happen with my car. (Rust issues not galling) I just use a tiny dab of anti-seize and torque to 103 ft lbs and it works just fine thank you. If i'm really torqueing to 112 ft lbs because its lubed...who cares? It's lug nuts!