Anti seize on lug nuts ?? Got a bad scare. Got lucky.

[srt]

What a good thread !  I'll pay more attention now to lugs than before.

Here's an anal-retentive question for you more engineer types.  If the lugs have always been torqued by an impact wrench (as seems to be the case whenever you take it to the dealer, midas, mr quick oil change etc..)  have the lugs been stretched into the plastic deformation region?  If so, will the original torque spec still give the right force to hold things where they should be?  How do we know?????

[Burlkraft]

The rule of thumb on truck wheels is a 3/4" air wrench and 6 clicks at 150 psi....... :D :D :D :D

Ya don't wanna be the next guy to try to crack those loose.... ;) ;)

Ya gotta love those air operated torque wrenches... :D :D :D :D

[scsmith42]

SRT - it depends upon the impact wrenches used and the people using them.  Today, many shops limit the maximum amount of torque by using torque bars.

Typically, once a bolt/stud reaches the plastic deformation stage, it will continue to stretch and far all intents and purposes it is ruined as an effective fastener.  To check for this, estimate the metal grade and look up the maximum torque range for that size bolt/stud.  Use a really good torque wrench to tighten it down, and feel to see if it starts "creeping" as you get near maximum torque. 

Typically a nut tightens progressively LESS as you increase the torque on it.  For instance, when tightening the nut on a 5/8 SAE Grade 8 stud, once you get to 30 ft.lbs of torque, it may turn 3/4 of a revolution getting from 30 to 40 ft. lbs.  Then, if may turn 1/3 of a revolution getting from 40 to 50 ft. lbs.  Then, it may turn 1/8 of a revolution getting from 50 to 60 ft. lbs, etc.

Re the example above, I'm estimating the amount of turns off the top of my head, but you get the picture.

Creep is when the amount of turns increase as you increase the amount of torque, rather than decrease.  When this happens, you have typically stretched into the plastic deformation region and the fastener is ruined.

This may not hold true in all instances, but it does for most.

[Quartlow]

Thats why I like the local tire shop, they run the nuts up till they hit and get out the torque wrench to tighten the studs.

[srt]

scsmith, 

Thanks for that explination.  It makes perfect sense. 

The increase in "spin"/unit torque is exactly the feeling I get when I over torque something and am a milli-second short of just plain wringing it off.  I've never used  torque wrench on a lug nut, but that's about to change. 

As a kid, I was standing outside my car while parked in a rest stop along the side of the road.  All the sudden my buddy shouted "LOOK OUT!".  I jumped just in time to be missed by a wheel and tire that had come off a guys trailer going down the road.  It hit the back of my car, and really messed it up.  The guy had torched out the center section of a wheel to fit his trailer hub.  That turned out to be a bad idea. 

The secone time, I lost a trailer wheel on Rt. 95, just North of the Baltimore beltway.  Again, operator error.  I failed to retighten the lugs at 50 and 500 miles after replacing a tire.  Fortunately, no one or thing was hurt, but if I hadn't been pulling that load of TJ's with a big heavy truck, with a brake controller, it might have been a different story.  That 16' tandem axle trailer had a mind of its own after being shorted by one wheel.

[scsmith42]

Something else to keep in mind - make sure that the metal grade for the nut is equal to or stronger than the metal grade for the bolt/stud.  Since the amount of torque is related to the strength of the bolt/stud (since that's what you're stretching), a nut of a lower grade may strip it's threads - either during torqueing or while in use.

If you buy a "click type" torque wrench (my personal preferance), be sure to set it back to zero or to it's minimum setting as soon as you're done using it.  If it's left set to a higher torque setting, it can lose it's calibration.

Regards,

Scott

[Larry]

Needed new tires for my truck so I went to the small town tire dealer I've been buying from for 10 years.  They didn't have my size of tire on hand but could get em the next day.  Had a funny feeling they were trying to jerk me around so went to Walmart.

Walmart had my size of tire...so put on 4.  I was the only guy there but took forever to get new tires.  Watched the guys work...and this is there standard way.  One guy uses a real torque wrench on the lug nuts...than a second guy comes along and checks the first guy.  And free rotation every 6,000 miles along with free repair on a flat...and still a second guy checks the first one's work.

I know a lot of people like to bash Walmart...but think they have earned my tire business.

And guess I learned from Dad who has been driving since 1935...clean and lube the lug nuts.  Only problem for the two of us was from a tire dealer who didn't torque the nuts properly.