Lug Nut Bolts Shearing Off

[bruceb58]

Re: Lug Nut Bolts Shearing Off

Me too....except in my case 30+ years.

Same here. I was doing it with no problem for 30+ years until I had my problem and learned the correct way...don't use lubricant.

 

[robert graham]

Re: Lug Nut Bolts Shearing Off

Maybe 2 successful ways of skinning the same cat?

 

[jeeperman]

Re: Lug Nut Bolts Shearing Off

To fred12..are these failures studs (protruding from hub) or bolts going into the hub?
Where exactly are they breaking............where the threads stop?

And on torque values beit wet or dry, do you all really think good, quality studs/bolts are designed with failure points that close to recommended torque values??
Certainly there is a substantual safety factor between the two figures.

 

[guy74]

Re: Lug Nut Bolts Shearing Off

Same here. I was doing it with no problem for 30+ years until I had my problem and learned the correct way...don't use lubricant.

So, you are saying that no stud that is put together dry will ever shear off? Just doesn't seem like a big enough sample, you had one failure in 30 years, to base knowlege to give others advice. You do it your way, I'll do it mine!!Btw, I use anti-seize on all of mine, and I am not going to change that!!

 

[robert graham]

Re: Lug Nut Bolts Shearing Off

If all studs/lug nuts wear tightened with an impact/torque wrench then the "no lubricant law" might apply to prevent over-tightening and breaking of the studs, but I tighten mine carefully by hand with that in mind, and no problems! And my lug nuts aren't all crusted over with rust/corrosion, which could on a bad day, weaken them. I have Never had a lug nut get loose or come off! Guess this is one of those endlessly debatable subjects......

 

[bruceb58]

Re: Lug Nut Bolts Shearing Off

Like I said before, amazing how when people are finally informed of the correct way of doing something, they all fall back to "I'll do it my way and I am not going to change that".

I tighten mine carefully by hand with that in mind, and no problems!

With a torque wrench or not? If you tighten a lug nut with a torque wrench to 80lbs with lubricant, you are over torquing. If you are just tightening without a torque wrench...wet or dry...you have no idea what you are torquing to anyway.

 

[skargo]

Re: Lug Nut Bolts Shearing Off

That's scary!...maybe some ever-zealous meatball with the impact wrench at the tire store. That's one reason I rotate my own tires! Glad you weren't hurt!

Thank you. I actually replaced the brakes on this car 2 months ago. I use an impact to remove, but ALWAYS tighten by hand. I wonder if they very slowly backed off? I did hit a monster pothole 2 weeks before this happened, yet I ignored the vibe, big mistake on my part...

 

[bruceb58]

Re: Lug Nut Bolts Shearing Off

I use an impact to remove, but ALWAYS tighten by hand.

You use a torque wrench when you tightened them up?

 

[dingbat]

Re: Lug Nut Bolts Shearing Off

The ultimate strength of the connection lies in yield strength of the bolt and friction plays a large role in how much torque is converted to preload. Besides the torque required to stretch the bolt, torque is also required to overcome friction in the threads and under the nut face. Typically, 10% to 15% of the torque is used to stretch the bolt, 30% is dissipated in the threads and 50% - 55% is dissipated under the nut face. Because friction is an important factor in the relationship between torque and preload, variations in friction have a significant influence on the bolts preload. Even different bolt surface finishes generally have different friction values.

In order to effectively utilize the strength of the bolt, yet leave some margin for any loading the bolt would sustain in service, an equivalent stress of 80-90% of yield is commonly used. Now look at some of the friction coefficients below. While we're working in the 80-90% percentage range some lubricates have the potential of increasing the stress on the bolt by as much as 50%

Bolt preload:

Pi = T/(K D)
where Pi = bolt preload
T = bolt installation torque.
K = torque coefficient.
D = bolt nominal shank diameter (i.e., bolt nominal size).

Torque coefficient K is a function of thread geometry, thread and collar coefficient of friction, interface materials, surface condition, and any lubricant (if any).

 

[bruceb58]

Re: Lug Nut Bolts Shearing Off

^^^^^^^Good description of what is happening but I am afraid it is still going to land on deaf ears where people have their preconceived ideas and aren't willing to change.

 

[guy74]

Re: Lug Nut Bolts Shearing Off

Well, I understand your arguement, but I still have to be able to get the nut off to change a flat. I just back the torque down to the minimum spec and use lube. I have been on the side of the road with 4 of 5 studs broken off trying to get the rusted on nuts off. It isn't a perfect world that I live in, and we have to make things work. Where I live the soil is very corrosive, and it has to be delt with. I appreciate your education, but I've read that info a million times, and know that it just doesn't work in practice here for anything that sees gravel or dirt. Clean and dry works good on new hardware in the lab or factory, but not well here in the lime dirt of Kansas.

 

[bruceb58]

Re: Lug Nut Bolts Shearing Off

I back my boat into saltwater. Not sure what soil is more corrosive than that. Of course I do preventative maintenance on my trailer and the lug nuts come off once a year so the nuts aren't going to have a real big chance of getting rusted on to the lug.

 

[H20Rat]

Re: Lug Nut Bolts Shearing Off

Well, I understand your arguement, but I still have to be able to get the nut off to change a flat. I just back the torque down to the minimum spec and use lube. I have been on the side of the road with 4 of 5 studs broken off trying to get the rusted on nuts off.

Sounds like you are due for a different method... Here is one that will ABSOLUTELY work for your situation. Take the wheels off, then take a wire brush to the studs and nuts, get everything 100% rust free. Install the wheels and torque to the middle of the range, DRY. Now, once everything is torqued down, pull the trailer around the block and double check your torque. Once you are done with that, paint the studs... yep, you heard right, paint 'em. Just a nice light coat, enough to cover bare metal.

I do this to my snowmobile tires, which see environments far worse than a boat tire ever will. Boat tires might get dunked into salt water occasionally, snowmobile tires get to drive in a salt environment pretty much any time the tire is rolling.

(I have NEVER broken a stud torquing to spec dry, and the nuts don't rust on.)

 

[guy74]

Re: Lug Nut Bolts Shearing Off

Why do YOU feel that I need a new way to do what has been done here since wheels started being bolted on model A's? There is no law or regulation against lubing wheel studs, and it has worked good for everyone around here for generations. What makes your way right, and our way wrong?
Besides that, this thread has gotten so far from the OP's problem, I just don't care for being preached at, I didn't ask a question, just offered what is common practice around here!!
I'm still curious as to why his studs failed in the driveway, I went out to the shop, and basically destroyed an old unit bearing hub that had studs still in it. 12mm stud survived a lubed torque of 140ft-lbs, before it yielded(didn't return to original length after removing the nut). The next one twisted off at 130ft-lb dry, then at 160ft-lb lubed pulled the head off the back of the stud. The next one yeilded at a dry 160ft-lb, last one stripped the threads at a dry 140ft-lb. I think about most topics, and don't speak about things I haven't had experience with. Since it has been a shop day, storming here, I decided to experiment a bit, and put some numbers out there. All measurements were with a certified Snap-on 1/2 drive click type wrench, and stud length was measured with a micrometer. The studs were in a unit hub from a 1993 trans-am with 285K miles when removed. Hows that for numbers Anyway, with good, although old, studs I wasn't able to replicate the OP's conditions with anything close to reasonable torque.
Still sounds like bad studs.

 

[elkhunter338]

Re: Lug Nut Bolts Shearing Off

You guys have missed one thing, a boat trailer in salt water rusts the lug nuts.
You need to use some anti rust stuff, anti sieze, grease, other.
You are right most torque values are for dry.
Search the internet and you can find torqe values for bolt sizes and grades, dry no lube, lightly oiled.
If you oil or they will list as waxed. Use the appropriate value and a good torque wrench.

I tighten my 1/2" boat lug nuts to 65lbs with light coating of grease or fluid film.
For example grade 8 1/2x20 (fine thread).
131/144/65 lb torque for plane steel/zinc/waxed(highly lubricated).

I assume wheel studs are grade 8, not 100% sure. I have this chart on my tool box.
proper bolt torque by zero fasteners. http://zerofast.com/torque.htm

 

[bigdee]

Re: Lug Nut Bolts Shearing Off

I too use anti-seize (use it on just about everything that needs to be disassembled at some point) 40+ years and no torque wrench except on some mag wheels I once had. I put the anti-seize on the threads only,not the shoulder of the nuts. When I was young a torque wrench was a luxury and most mechanics had enough common sense to be able tighten a wheel without one! Lubrication on threads has little effect with how well the bolt/nut holds.....it is torque and the slight bolt stretch that determines the holding power of a fastener. But come on people, putting on a wheel is not rocket science.

 

[rbh]

Re: Lug Nut Bolts Shearing Off

Back to the question of "why the lug failed"???????


CHEAP HARDWARE, you get what you pay for.

 

[bigdee]

Re: Lug Nut Bolts Shearing Off

Back to the question of "why the lug failed"???????


CHEAP HARDWARE, you get what you pay for.

You are probably correct....torqueing to 80 Ft Lbs on a 1/2" non SAE bolt is scary!

 

[rbh]

Re: Lug Nut Bolts Shearing Off

You are probably correct....torqueing to 80 Ft Lbs on a 1/2" non SAE bolt is scary!

Trying to remember are lugs grade 8 or 5????

#8 are stronger but brittle, #5 not as strong as #8 but have more give, not as brittle????


Dang bald timers!!!

 

[bigdee]

Re: Lug Nut Bolts Shearing Off

Trying to remember are lugs grade 8 or 5????

#8 are stronger but brittle, #5 not as strong as #8 but have more give, not as brittle????


Dang bald timers!!!

Yup that is correct but is an 8 REALLY an 8? that is the question with these low cost Chinese fasteners. And dang it ! I am almost a bald timer too!!