Lugnuts Falling Off

SN95GT50 · May 29, 2006

I have a 95 GT with 98 Cobra Rims (not R's).

A month or so ago I noticed I was missing a lugnut front pass side. Checked the others and they were fairly tight, but, by no means tight enough. Figured I forgot to tighten them. Pulled out the torque wrench and torqued them to 95 lbs same as other 3 wheels. Tonight I was cleaning my rims and noticed my wheel lock was loose again on the same wheel. Again, re-torqued them and will continue to watch this one wheel, but, what can cause this? The other 3 wheels are showing no indication of this problem.

I am still only running 4 lugs, where can I get some new lugs that will match the old ones? What is the thread etc to know when I purchase new ones?

SN95GT50

urban96 · May 29, 2006

what are you TQing them down to?

99FiveOh · May 29, 2006

SN95GT50 said:
Pulled out the torque wrench and torqued them to 95 lbs same as other 3 wheels.

the recommended torque is 95-105 ft.lbs

281pony · May 29, 2006

he said 95 lb.

seems like it might be an alignment problem and they are vibrating loose? do you notice any excess vibration?

urban96 · May 29, 2006

my bad

SN95GT50 · May 30, 2006

Haven't noticed an alignment problem, I was wondering about a balancing problem. I need new rubber for the rear and I am going on a business trip tomorrow (mileage will pay for a pair), I will have them check the alignment and balance then. I will keep the torque wrench in the car and check a few times along the way.

I see Mustangs unlimited has the same set of lugs that I have, a full set for ~$30, I will stop by there on my way home and pick up a set, atleast I will then be back to 5 lugnuts on that wheel.

Thanks,
SN95GT50

scarless · May 30, 2006

Do you have grease or anti-seize on the threads? If so, clean them off.

illwood · May 30, 2006

SN95GT50 said:
I see Mustangs unlimited has the same set of lugs that I have, a full set for ~$30, I will stop by there on my way home and pick up a set, atleast I will then be back to 5 lugnuts on that wheel.

Thanks,
SN95GT50

Stinks that you have to buy a full set. Are you in the Manchester CT area? 'Cause I work about 15min away.

scarless said:
Do you have grease or anti-seize on the threads? If so, clean them off.

I always put a little anti-seize on the threads. It's the only way to get a proper torque reading (same as on head bolts, main caps. . .) The torque should hold the lugnuts in place. I re-torque mine every few thousand miles and find that on average, on on each wheel has worked its way down to about 80 ft-lbs from the 95 ft-lbs that I torque mine to.

Therian · May 30, 2006

Go with the gorilla set...I've got them on, and they seem to work well. Price is right. ask someone to drive behind you and make sure your tires are balanced well

SN95GT50 · May 31, 2006

I stopped at Mustangs Unlimited (Lawrenceville, GA Store). They had a set of 5 lugs for $9. I am back to having all 5 on each wheel. I also had 2 new tires put on the rear last night (they were completely bald), I had them re-balance the front wheels while they were in there. I will be putting on about 550 miles today for a meeting, I have the torque wrench in the car and will check frequently. Hopefully the balancing will do the trick.

Thanks,
SN95GT50

GRGT1994 · May 31, 2006

illwood said:
I always put a little anti-seize on the threads. It's the only way to get a proper torque reading (same as on head bolts, main caps. . .) The torque should hold the lugnuts in place. I re-torque mine every few thousand miles and find that on average, on on each wheel has worked its way down to about 80 ft-lbs from the 95 ft-lbs that I torque mine to.

Not right, please stop doing this. Putting anti-seize or any other lubricating medium changes the torque reading. You are now putting far more stress on your lugs that is recommended. I'm surprised you haven't broken one. But since your lugs have been improperly stressed, you risk a catastrophic failure. If I were you, I replace all the lugs. SERIOUSLY!

You are right that some torque specs specify lubricant. But some do not. And the do not for a REASON. A small part of that reason is that lubricants improve the precision of certain critical engine bolts (head bolts, main caps). The biggest impact of using or not using lubricant is clamping force. There is a huge difference between the clamping force of a bolt tightened to 95 foot pounds without lubricant compared to one with lubricant. And generally bolts are designed to fail if too much clamping force is applied.

Maybe I'm missing something. Maybe an engineer could chime in here. But something just sounds critically wrong about putting lubricant (or anti-seize) on wheel lugs.

mo_dingo · May 31, 2006

GRGT1994 said:
Not right, please stop doing this. Putting anti-seize or any other lubricating medium changes the torque reading. You are now putting far more stress on your lugs that is recommended. I'm surprised you haven't broken one. But since your lugs have been improperly stressed, you risk a catastrophic failure. If I were you, I replace all the lugs. SERIOUSLY!

You are right that some torque specs specify lubricant. But some do not. And the do not for a REASON. A small part of that reason is that lubricants improve the precision of certain critical engine bolts (head bolts, main caps). The biggest impact of using or not using lubricant is clamping force. There is a huge difference between the clamping force of a bolt tightened to 95 foot pounds without lubricant compared to one with lubricant. And generally bolts are designed to fail if too much clamping force is applied.

Maybe I'm missing something. Maybe an engineer could chime in here. But something just sounds critically wrong about putting lubricant (or anti-seize) on wheel lugs.

I am no engineer but I work on RV's, and we NEVER put antisieze on lugnuts. That includes trailer wheels and the gigantic wheels on the 45' RV's.
Scott

illwood · May 31, 2006

GRGT1994 said:
Not right, please stop doing this. Putting anti-seize or any other lubricating medium changes the torque reading. You are now putting far more stress on your lugs that is recommended. I'm surprised you haven't broken one. But since your lugs have been improperly stressed, you risk a catastrophic failure. If I were you, I replace all the lugs. SERIOUSLY!

You are right that some torque specs specify lubricant. But some do not. And the do not for a REASON. A small part of that reason is that lubricants improve the precision of certain critical engine bolts (head bolts, main caps). The biggest impact of using or not using lubricant is clamping force. There is a huge difference between the clamping force of a bolt tightened to 95 foot pounds without lubricant compared to one with lubricant. And generally bolts are designed to fail if too much clamping force is applied.

Brad, I appreciate your concern (and the email), but I am pretty confident that anti-seize isn't going to cause my lugnuts to fall off. I've had more problems with wheel studs getting a little rust on them and getting a false torque reading on them (when installing them dry) that causes them to rattle free after only a few miles.

GRGT1994 said:
Maybe I'm missing something. Maybe an engineer could chime in here. But something just sounds critically wrong about putting lubricant (or anti-seize) on wheel lugs.

Does having a Bachelor's Degree and finishing a Master's part time in Mechanical Engineering work for ya?

I don't have the appropriate texts infront of me, but I can look it up more info on the matter and post it later. I tried to google some information, but it was so mixed up between truth and internet myth that I didn't want to reference it. Maybe Grady will chime in as well.

GRGT1994 · May 31, 2006

Illwood, you probably know far more than I do. I start from that assumption. You clearly have the degrees. And after all, my automotive/mechanical knowledge comes almost purely from what I read on StangNet. Just trying to keep you safe.

Still, I seem to remember reading something about torque readings when I was doing my HCI kit that pointed out how significantly different clamping loads would be with and without lubrication. And antiseize lubricates.

BTW, on your first comment about antiseize causing your lug nuts to fall off, I hope I was clear that that was not my concern. I was concerned that your lugs would break off due to being over stretched as a result of too much clamping force (so technically the lug nuts would fall off if I were right - along with the broken lugs and your wheel ).

illwood · May 31, 2006

GRGT1994 said:
Illwood, you probably know far more than I do. I start from that assumption. You clearly have the degrees. And after all, my automotive/mechanical knowledge comes almost purely from what I read on StangNet. Just trying to keep you safe.

Still, I seem to remember reading something about torque readings when I was doing my HCI kit that pointed out how significantly different clamping loads would be with and without lubrication. And antiseize lubricates.

BTW, on your first comment about antiseize causing your lug nuts to fall off, I hope I was clear that that was not my concern. I was concerned that your lugs would break off due to being over stretched as a result of too much clamping force (so technically the lug nuts would fall off if I were right - along with the broken lugs and your wheel ).

All is good Brad. In all honesty, it's nice to know that there are people on Stangnet that are concerned for others personal (and vehicular) safety. :SNSign:

I don't want to get all high and mighty "Oooh, I have a degree" ('cause I hate those types of people). For the sake of curiosity, I'm going to try to get the equations to calculate the bolt stretch to figure it out whether it's safe or not mathematically. I'll post my findings so we can have something better than inter-myths.

On a similar interesting mechanical fastener topic. Did you know that too low a torque on head bolts will cause them to not back off, but actually fail vs. proper torque? Basically, during the combustion process, the bolts go through cyclic loading. If the bolts aren't torqued enough to yield (stretch), then they yield and unyield from the combustion cycle and fail due to fatiuge. When the the bolts are yielded to begin with (properly torqued), the forces from the combustion process are lower and the bolts aren't subjected to a fatigue failure mode. (I'm going to have to double check to make sure my explanation is 100% accurate, but you get the idea)

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