Lugnut Torque Question

[lynnmor]

An engineer is trained to fret and worry about everything.

And the job of the consumer is to find new and better ways to destroy anything.  ???

 

[jubileee]

  I promised myself I?d stay out of this discussion when it started,but I can?t stand it any longer. The right/ left threads on the big rigs started going away (for me the mid-late nineties) with the advent of hub piloted wheels versus the stud piloted wheels which were used  from the beginning of modern trucking and are still used today.
  Took about 10 years for the hub piloted right hand thread only design to become fully accepted in the trucking industry and over come the fear of wheel separation which happened a lot until people realized they had to be properly torqued.
  Hub piloted wheels demanded proper torquing while you could get away just ? hammering up? the inner/ outer/left/right stud piloted system. You could always tell if you had a loose lug(s) on the old system because rust streaks would appear around the loose lug. If left loose, the wheel would eventually crack around lug bolt hole.
  When I first went to hub piloted wheels on my trucks, I checked the torque constantly. The right hand side
always took a little tightening. This is the side that would have left hand threads on the old system.
    Other thoughts, I believe race track only knock off wheels are still left/right thread. And, my ?92 Bounder had hub piloted wheels which I always torqued. I?m not sure when light duty trucks made the switch. Also, hub piloted wheels can be hard to center and if not centered can cause vibrations and other problems usually diagnosed as bad wheel balance. Tools are made to properly center the wheels ,but are time consuming and seldom used in a commercial tire shop.  Vibrations caused by off centered wheels can be covered up by wheel balancing for the most part, but not abnormal tire wear.

 

[sightseers]

I read somewhere Detroit Automotive Engineers back in the old days said that it was a "Mechanical Impossibility"  for a car to ever go 120 mph in the 1/4 mile.....

engineers are now saying,  you must not only tighten,  but correctly 'torque' down the lug nuts or people will be dying everywhere  ...

 

[lynnmor]

engineers are now saying,  you must not only tighten,  but correctly 'torque' down the lug nuts or people will be dying everywhere  ...

People that care understand that you don't "torque down" a fastener, instead they know to tighten to a specification that results in the best margin of safety and performance.  Some might prefer ignorance over knowledge.

 

[sightseers]

is it knowledge or fear. 

I know out on the ocean there are these giant rouge waves that can capsize even the biggest cruise ships !

.....but I'm not going to wear a life-jacket at the dinner table...  ;D

 

[FastEagle]

Hello everyone,

This may be an obvious question but I keep seeing torque recommendations expressed as "Stage 1, Stage 2 and Stage3"

Could someone please explain what these stages mean? My guess is that you tighten all wheels to the Stage 1 level before next tightening all wheels to the next stage level and so on... but I could be way off

Thanks!

The reference below is an excerpt from a Prime Time owner's manual. It discusses your lug nut torque.

Safety items are mandated to be in all owner's manuals.

https://forestriverinc.help/#/primetimerv/guide/2019/750-lacrosse/search/topic/GUID-0BF84AC8-1047-4534-8956-A0719F880F15

 

[zmotorsports]

These comments about torque not being critical and an engineer's way of complicating things to take mechanical common sense out are incorrect.  After wrenching professionally as an industrial maintenance mechanic for 30+ years, OTR trucks and owning my own performance shop for 20 years I would never think to let something go out that I worked on that wasn't correctly repaired and the proper torqueing of fasteners is part of that proper repair.  Fasteners and components have a specific torque required to ensure the component will function correctly.  Granted I have NOT agreed with everything engineers have done in my line of work but proper torque specs are one thing I am somewhat anal about.

People many times think wheel torque is merely to prevent the wheel from falling off.  That is only partially correct.  The real reason proper torque is important is because when installing a wheel onto a hub which usually has a rotor sandwiched in between, the torque must be even and pull everything down evenly because when the assembly heats up, and being connected to a rotor it WILL heat up, the metal on a molecular level can and will move about.  IF there are uneven forces on the fasteners the metal will move about unevenly therefore leading to rotors being warped and possible even a wheel if the heat is high enough to transfer through to it.

When talking components that have gaskets in between them torque is even more critical to ensure the forces are spread evenly to seal properly and also distribute load evenly.

It always kills me to hear of people who shrug off torqueing fasteners as some kind of "above everyone else" because they disregard the engineers spec's, almost like a right of passage.  This is not only lazy and inaccurate it can be dangerous as well.  Granted I've been wrenching professionally for several decades and I have a pretty good feel for what a torque spec is based on feel but not that I would want to go throughout my days relying only on feel alone.  A properly cared for and repetitive torque wrench is invaluable and I make sure ALL of mine are accurate and properly stored and cared for.

Put another way, the same people that say torque spec's are over-rated, if you took a vehicle to a shop to have a job done professionally and then went to pick it up and was told "yeah we just cranked down on the head bolts as hard as we could, you'll be fine".  Would that invoke much confidence in the repair that it will last?  Why is it ok to shrug it off on a forum to sound cool yet refuse to have someone do that to your asset at a shop?  Would you demand that the mechanic torque the fasteners properly if you were in fact paying for the repair?  If so, why is it ok not to do it yourself?

Just food for thought.

Mike

 

[Memtb]

    Well said Mike! Of course....thread condition ( rust, dirt, etc.) must be taken into consideration.  Which, will alter torque  values....which, as you know is difficult to determine! In a perfect world, for those of us with unlimited resources, all studs and fasteners (nuts) should be replaced after each use....which is only practical in ?crital? systems. For those of us, that will use ?torque specs?, on less than perfect bolts/studs/fasteners....my ?rule of thumb? is torque spec +5%. Yes, it?s a guess, but better than using no torque specs at all....which many are content with!

 

[catblaster]

Would anyone like for me to put their engine together by "feel"? Doesn't torquing the rods and mains merely keep the guts from slinging out.

 

[sightseers]

actually there are hundreds of old films of factory auto workers assembling engines with just hand wrenches...

The longer the wrench the tighter the bolt.

this is a cool old film ...https://www.youtube.com/watch?v=L40MaCjqY5w

 

[Old_Crow]

These comments about torque not being critical and an engineer's way of complicating things to take mechanical common sense out are incorrect.  After wrenching professionally as an industrial maintenance mechanic for 30+ years, OTR trucks and owning my own performance shop for 20 years I would never think to let something go out that I worked on that wasn't correctly repaired and the proper torqueing of fasteners is part of that proper repair.  Fasteners and components have a specific torque required to ensure the component will function correctly.  Granted I have NOT agreed with everything engineers have done in my line of work but proper torque specs are one thing I am somewhat anal about.

People many times think wheel torque is merely to prevent the wheel from falling off.  That is only partially correct.  The real reason proper torque is important is because when installing a wheel onto a hub which usually has a rotor sandwiched in between, the torque must be even and pull everything down evenly because when the assembly heats up, and being connected to a rotor it WILL heat up, the metal on a molecular level can and will move about.  IF there are uneven forces on the fasteners the metal will move about unevenly therefore leading to rotors being warped and possible even a wheel if the heat is high enough to transfer through to it.

When talking components that have gaskets in between them torque is even more critical to ensure the forces are spread evenly to seal properly and also distribute load evenly.

It always kills me to hear of people who shrug off torqueing fasteners as some kind of "above everyone else" because they disregard the engineers spec's, almost like a right of passage.  This is not only lazy and inaccurate it can be dangerous as well.  Granted I've been wrenching professionally for several decades and I have a pretty good feel for what a torque spec is based on feel but not that I would want to go throughout my days relying only on feel alone.  A properly cared for and repetitive torque wrench is invaluable and I make sure ALL of mine are accurate and properly stored and cared for.

Put another way, the same people that say torque spec's are over-rated, if you took a vehicle to a shop to have a job done professionally and then went to pick it up and was told "yeah we just cranked down on the head bolts as hard as we could, you'll be fine".  Would that invoke much confidence in the repair that it will last?  Why is it ok to shrug it off on a forum to sound cool yet refuse to have someone do that to your asset at a shop?  Would you demand that the mechanic torque the fasteners properly if you were in fact paying for the repair?  If so, why is it ok not to do it yourself?

Just food for thought.

Mike

Thank you!!!  Same thing I've been trying to say, but so much more eloquent than I can be.
 
Shops who do sloppy work like that are the shops which cause the public to think that all mechanics are ripping them off.

 

[sightseers]

on high performance engines, the engineers will say you can only torque, or tighten down the rod bolts once. They are never to be used again and the correct torque is measured by the bolt stretch length .. 

 

[Memtb]

                  )

 

[Old_Crow]

on high performance engines, the engineers will say you can only torque, or tighten down the rod bolts once. They are never to be used again and the correct torque is measured by the bolt stretch length ..

Yup, the whole "torque-to-yield" thing started back in the 90's sometime.  I think the first engine that I can remember with the disposable bolts was the old GM Quad-Four.  Most of the techs I know hated that motor because it was such a PITA to work on, and there was practically no way to beat flat rate on that motor, even on such a simple job as a thermostat. 
I always looked at them as a challenge and just did the job. 
Heck, that's how I got to be a motor home mechanic.  No one else in the dealership wanted to work on them, but I would.

 

[zmotorsports]

on high performance engines, the engineers will say you can only torque, or tighten down the rod bolts once. They are never to be used again and the correct torque is measured by the bolt stretch length ..

^^Exactly.  The most accurate and preferred means to measure any fastener is by the stretch but seeing as how the only way to measure stretch is by having access to the entire length of the fastener such as through a weldment, the next best way and most common is by using a torque wrench and tightening to an engineered specification which is why I still prefer to torque fasteners to the correct spec.  I don't like to wing it.  Now have I tightened bolts without a torque wrench?  Absolutely.  I'd be lying if I said otherwise.  However, on critical fasteners that should be torqued, that is why I purchased torque wrenches and follow the sequence to avoid costly and unnecessary repairs.

Mike

 

[SargeW]

I am surprised in this thread my personal reason for proper torque wasn't described. I had my 08' Jeep Rubicon tires rotated regularly. I did it myself, or if available I had a tire shop do it. While up in Oregon a few years back I had my tires rotated at a Les Schawb. I had purchased the tires there 2 years before, and they included free lifetime tire rotation.

I pulled in and waited outside while the tech pulled the tires off and rotated them to my specifications. They finished in about 15  minutes and I was on my way. About 4 months later on the way back to Ca we stopped in Death Valley and took a trip out to the "Race Track".  The place in Death Valley where the rocks seem to slide across the desert floor all by themselves.  It was about 15 miles down some really washboard roads and zero cell signal. We went down and back in one afternoon. Actually the trip destroyed my battery, but that's another story. 

Getting back to my stick house a few days later, I went to the garage to do another rotation. When trying to remove the lug nuts I discovered that most of them were hopelessly stuck. Using a breaker bar and a 3' cheater, I snapped a few of the lugs trying to loosen them.  Apparently the tire jockey used an impact wrench to put on and seat the lugs after the rotation. All of the lugs were eventually replaced as they were put on so tight that the threads were stretched.

When I contacted  the Manager of the Les Schawb, he was nice about it, but commented that the lugs were checked with a torque wrench after being installed as a matter of practice. But here is the problem. The lugs should have been torqued to 90 foot pounds. If the impact wrench is not set correctly, or malfunctions, and puts the lug on to 200-300 ft lbs, the torque wrench will still "click" when it hits it 90 lb setting. AND YOU WILL NEVER KNOW.

I included that bit of info about Death Valley because if I had gotten a flat while out at the Race Track, we would have been screwed. Having a spare tire is useless if even 1 lug is stuck and won't come off. 

Moral of the story is, don't EVER let anyone install the lugs with a impact wrench on any vehicle, other than a motor home with 22.5 wheels. They are set to over 400 ft lbs, and need a high torque impact to get them off anyway. The use of a torque wrench just tells you that the wheel is at a minimum required tightness, not what the maximum may be. 

 

[Memtb]

  This is and continues to be a ?big? problem when on the road. The ?tire jockey? knows he will never see you again....and doesn?t have to worry about having his face planted in the parking lot. Also....you can?t fix stupid, 

 

[kdbgoat]

The lugs should have been torqued to 90 foot pounds. If the impact wrench is not set correctly, or malfunctions, and puts the lug on to 200-300 ft lbs, the torque wrench will still "click" when it hits it 90 lb setting. AND YOU WILL NEVER KNOW
Moral of the story is, don't EVER let anyone install the lugs with a impact wrench on any vehicle, other than a motor home with 22.5 wheels. They are set to over 400 ft lbs, and need a high torque impact to get them off anyway. The use of a torque wrench just tells you that the wheel is at a minimum required tightness, not what the maximum may be. 

Exactly, see post #19