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Topic: Damaged lug bolts (Read 1656 times) previous topic - next topic

Damaged lug bolts

We're at MOT getting service on our brakes.  When the guys went to put the wheels back on the front, they found three bolts that could not be torqued to the 400-foot-pounds they use here.  The bolts had to be replaced at considerable effort and cost. 
When looking at the bolts with the lug nuts on one can see in the attached photo that two are out further... stripped.  As Keith Risch (MOT master tech)  explained, the problem occurs when someone puts excessive torque on the nuts. Like with an air driver set too high.  Since the bolt is smaller in diameter on the inside where the inner nut holds it in place, this is where the damage occurs.  Best to used the air driver to put on the nuts with moderate tightness, then torque them as shown in the pic.  So who did this?  The front tires were replaced by Herman Power last year about this time. 

I will have more to say about service at MOT and Keith in particular.  Excellent!  That has not been the case with other services we have had here in Nac.

Re: Damaged lug bolts

Reply #1 –
When Herman Power replaced the tires on a rig we had a number of years ago they used only an impact wrench. I asked the tech what he was torquing the bolts and he replied that he just turned up the gun as high as it would go. I didn't know any better at the time. Disappointing that they are still not torqueing properly.
jor

Re: Damaged lug bolts

Reply #2 –
400# lubed may be too high .  Look up the nominal spec for the retainer  nut size.  My bet is 300# max. 
 Always better to hand tighten for final torque of course. 

Re: Damaged lug bolts

Reply #3 –
Something else other than lug nut torquing going on there. The threads that would have been up against the inside of the hub are still good. That stud is pulled into the hub and the serrations lock it if the smaller nut on the inside is tight. Looks like the someone stripped the threads trying to put the stud in.

Re: Damaged lug bolts

Reply #4 –
Right . Almost looks like it was never fully seated.

Re: Damaged lug bolts

Reply #5 –
Thanks for the input.  There were six bolts that had to be replaced on the front wheels.  So it likely happened as I described... over tightening the lug bolts.  I took the bolts to Herman Power and talked to Craig Power.  Without hesitation, he said to bring him the bill and they would cover the cost.  He also said they try to closely monitor the torque of their impact tools, but sometimes problems occur. 

I asked one of the MOT crew about the 400 ft pounds torque that they use and they confirmed that is what should be used.

Re: Damaged lug bolts

Reply #6 –
Be sure to differentiate between 400 lb-ft DRY vs LUBED.  Big difference!

And, with Aluminum wheels, they need to be retorqued after a few hundred miles.

Re: Damaged lug bolts

Reply #7 –
They are dry, not lubed.

George

Re: Damaged lug bolts

Reply #8 –
Correct.

But, have seen "Bubbas" slap grease on them then use an impact.

I know, you have met Bubba!

Re: Damaged lug bolts

Reply #9 –
And to this topic, I have never had a shop use a torque wrench. I doubt many of them even own one that is properly calibrated. So what must one do.

Re: Damaged lug bolts

Reply #11 –
When you over torque a stud or bolt it will stretch.  This is called necking as the stretched part is narrower and the thread pitch changes.  Running the nut onto the stud will show if this is the case as it will jam.  Often it's running the nut on a stretched bolt that causes it to strip.  It's OK to use an impact for running the nut up or off.  It's not OK for final tightening.  When I had my front tires replaced they used a torque wrench both on installation and when rechecking the torque 100 miles later.

In my past life with large fleets we always used a torque wrench on critical items like wheels.  The wrenches were regularly checked against a reference unit.

Here is Alcoa's wheel service manual with everything you need to know.

https://www.arconic.com/alcoawheels/catalog/pdf/servicemanual-english.pdf

Keith

Re: Damaged lug bolts

Reply #12 –
Socket, 3/4" breaker bar, regular 1/2" torque wrench and 5' thick wall iron pipe with 1/2" socket welded into one end: Torque Wrench extensions

You will need some kind of stand and extension to get in far enough to reach the nuts on the rear wheels.

With this, even a 100 pound weakling can properly torque the lug nuts. No expensive tools needed.

Used this for the last two decades with a "custom upgrade"/elegant one made by a fellow Foretravel owner that even has a set screw for holding the handle of the breaker bar in the pipe.

On mine, 400 lb-ft requires a torque wrench setting of 94 lb-ft-- this is dependent of the length of the pipe with longer pipe requiring less input torque.

Re: Damaged lug bolts

Reply #13 –
Lubed is much better and fights corrosion .

Re: Damaged lug bolts

Reply #14 –
Quote from: Protech Racing –
Lubed is much better and fights corrosion .

But, one would have to KNOW how much to lower torque specs when going from factory recommended "dry" to "lubed".

Said another way, lubing and using dry torque specs will over-stretch the bolt!

Re: Damaged lug bolts

Reply #15 –
Quote from: wolfe10 –
Used this for the last two decades with a "custom upgrade"/elegant one made by a fellow Foretravel owner that even has a set screw for holding the handle of the breaker bar in the pipe. On mine, 400 lb-ft requires a torque wrench setting of 94 lb-ft-- this is dependent of the length of the pipe with longer pipe requiring less input torque.
If you ever want to get rid of it, I know a coach that would love to have it back!  :))

Re: Damaged lug bolts

Reply #16 –
Hummm..... I was at Hermann power tire yesterday dealing with a defective tire. My next stop was at the mothership to get a replacement lug bolt that was found damaged when I replaced the defective tire last week. Herman power put the tires on 1.5 years ago.... does anyone see a trend here...

Re: Damaged lug bolts

Reply #17 –
Alcoa gives lubed value.  About 100# less . or 300+-25.

Re: Damaged lug bolts

Reply #18 –
My files show that 12 of them were replaced the last time fresh Michelins were done in 2014.

Re: Damaged lug bolts

Reply #19 –

That's why I never let a tire shop air gun our wheels. If you use a little Anti-Sieze Amazon.com: never sieze on the threads, you can torque to 20 percent less and sure the nuts will come off easily.

Our forum is full of shop mistake posts. A big reason to do as much as you can yourself.

Pierce

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