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andybla
Samba Member
Joined: March 03, 2014
Posts: 630
Location: BE
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 Posted: Wed May 25, 2022 1:40 pm Post subject: Tightening torques |
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Hello,
I’m assembling my chassis components like front and rear axle, i torque them to spec with the help of the without guesswork book..
The problem is, the bolts seem to “stretch” or come loose.. i can apply proper torque to them, leave it for the night but the next day if i double check them, i can again turn them for example another 1/4 untill the torque ratchet clicks again..
Is this normal behaviour? Should i keep re torqueing them untill they finally click immediate after multiple periods of time? Any help pls? |
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busdaddy
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Joined: February 12, 2004
Posts: 51125
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Wed May 25, 2022 2:14 pm Post subject: Re: Tightening torques |
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What particular joints are you referring to?, any paint or powdercoat between the components?, oil or anti seize on the threads?
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12708
Location: Western Canada
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| Posted: Wed May 25, 2022 3:11 pm Post subject: Re: Tightening torques |
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That should be unnecessary. I suspect a faulty torque wrench or a faulty procedure.
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Pruneman99
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Joined: February 22, 2012
Posts: 5013
Location: Oceanside
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| Posted: Wed May 25, 2022 3:49 pm Post subject: Re: Tightening torques |
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| Playdoh quality aftermarket fasteners? |
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andybla
Samba Member
Joined: March 03, 2014
Posts: 630
Location: BE
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| Posted: Thu May 26, 2022 12:22 am Post subject: Re: Tightening torques |
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At this moment the subframe bolts
I uses a dot of copper paste as an anti seize, the parts have been painted but only two thin layers with a spray can, and i’m using aftermarket zinc plated bolts
The torque wrench is a facom
And in the end it works, when i re torque the bolts they click immediate, but the strange thing is that i need to redo this 5-6-7 times … |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12708
Location: Western Canada
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| Posted: Thu May 26, 2022 2:15 am Post subject: Re: Tightening torques |
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I use either a drop or two of oil or in most cases Kopper Kote anti-seize on every bolt. A dry thread will seldom give a proper torque due to friction. Friction is not your friend! Reduce it were ever possible.
My torque wrench is a Snap On brand, click style and I find that on occasion it will miss the click and go beyond what I set it for especially in the lower range. You get a feel for it and just know when it happens. Then I just back it off and try again. When torqueing a bolt you should come up to proper torque in one smooth motion without stopping. If you stop then it takes more torque to get it started moving again due to - yes - friction.
As far as re-torqueing things, I rarely do but when I do, again I back it off a ways first and only then come back up on the proper torque in a smooth motion without stopping.
Not sure if this helps...
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Abscate
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Joined: October 05, 2014
Posts: 22640
Location: NYC/Upstate/ROW
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| Posted: Thu May 26, 2022 3:03 am Post subject: Re: Tightening torques |
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| Quote: |
| When torqueing a bolt you should come up to proper torque in one smooth motion without stopping. |
That’s why all that retorquing you have done has now overtightened your fasteners. Post up upthread size, grade, and source of the fasteners , if you lubed them m and the torque value and we can tell you if you are in the badlands. Probably not. Typical torques in automotive are about 2x below the fastener or thread fail region.
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andybla
Samba Member
Joined: March 03, 2014
Posts: 630
Location: BE
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| Posted: Thu May 26, 2022 3:29 am Post subject: Re: Tightening torques |
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Thanks for the info so far everyone!
The bolts are TY brand 10.9 grade i bought from some german store.. (even though the original VW would be grade 8.)
subframe has m10x1.5 and m8x1.25
they were lubed with a small dot copper paste
the m10 are torqued with 31 ftlb
the m8 are torqued with 14 ftlb
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[email protected]
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Joined: February 12, 2003
Posts: 510
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| Posted: Thu May 26, 2022 6:19 pm Post subject: Re: Tightening torques |
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| Are you using a proper torque sequence? |
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TDCTDI
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Joined: August 31, 2013
Posts: 12848
Location: North Carolina
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| Posted: Thu May 26, 2022 6:52 pm Post subject: Re: Tightening torques |
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| oprn wrote: |
I use either a drop or two of oil or in most cases Kopper Kote anti-seize on every bolt. A dry thread will seldom give a proper torque due to friction. Friction is not your friend! Reduce it were ever possible.
Not sure if this helps... |
Actually, this causes you to over torque your fasteners, it is suggested that you should reduce the torque spec by over 50% if you do lubricate them.
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Abscate
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Joined: October 05, 2014
Posts: 22640
Location: NYC/Upstate/ROW
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| Posted: Thu May 26, 2022 10:47 pm Post subject: Re: Tightening torques |
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You are fine. You are well below the failpoint on a 10.9
I usually mark subframe bolts and watch them for movement but that’s pretty paranoid.
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oprn
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Joined: November 13, 2016
Posts: 12708
Location: Western Canada
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| Posted: Sun May 29, 2022 5:08 am Post subject: Re: Tightening torques |
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| TDCTDI wrote: |
| oprn wrote: |
I use either a drop or two of oil or in most cases Kopper Kote anti-seize on every bolt. A dry thread will seldom give a proper torque due to friction. Friction is not your friend! Reduce it were ever possible.
Not sure if this helps... |
Actually, this causes you to over torque your fasteners, it is suggested that you should reduce the torque spec by over 50% if you do lubricate them. |
Could you provide some backup data on that statement please?
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Abscate
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Location: NYC/Upstate/ROW
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| Posted: Sun May 29, 2022 11:10 am Post subject: Re: Tightening torques |
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A fastener is usually designed to give a design clamp force. You use torque to estimate the clamp force since it’s easier to measure torque.
When you tighten a fastener , as it makes head contact, the friction comes roughly equally ftom three places ..
Thread friction
Fastener head to surface friction
Fastener tension
Oiling a fastener reduces thread friction with little impact on the other chiebe the same force with about 2/3 the measured torque.
I’ve always used 1/3 to derate a dry torque rating with lube but50% is certainly in the ballpark
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mukluk
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Location: Clyde, TX
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| Posted: Sun May 29, 2022 12:42 pm Post subject: Re: Tightening torques |
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| oprn wrote: |
| TDCTDI wrote: |
| oprn wrote: |
I use either a drop or two of oil or in most cases Kopper Kote anti-seize on every bolt. A dry thread will seldom give a proper torque due to friction. Friction is not your friend! Reduce it were ever possible.
Not sure if this helps... |
Actually, this causes you to over torque your fasteners, it is suggested that you should reduce the torque spec by over 50% if you do lubricate them. |
Could you provide some backup data on that statement please? |
https://www.engineeringtoolbox.com/torque-lubrication-effects-d_1693.html
FYI, not sure if the same applies for VW service manuals, but in military aviation it has been standard practice that all listed torque specs are for clean and dry fasteners only unless it's clearly stated to oil or otherwise lubricate them before assembly within that system or specific task. Lubing fasteners when the torque spec is for installing dry will result in overtorquing the fastener, with possibly catastrophic effect depending on where it's located.
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Abscate
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| Posted: Mon May 30, 2022 2:40 am Post subject: Re: Tightening torques |
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Just pass on an interesting anecdote. BMW specifies dry torque for brake caliper fasteners and has written memos forbidding the use of lube on them ( per my service advisor) , in theNortheast m every bmw service group will stilllube them. You have to balance the engineer who wants a precise torque procedure with the needs of the next customer who won’t want to pay fir a drill out of a seized or snapped caliper bolt.
Same debate goes on with lugnuts with the dry vs lubed camps thumping their chests on Fora.
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oprn
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| Posted: Mon May 30, 2022 4:15 am Post subject: Re: Tightening torques |
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| mukluk wrote: |
https://www.engineeringtoolbox.com/torque-lubrication-effects-d_1693.html
FYI, not sure if the same applies for VW service manuals, but in military aviation it has been standard practice that all listed torque specs are for clean and dry fasteners only unless it's clearly stated to oil or otherwise lubricate them before assembly within that system or specific task. Lubing fasteners when the torque spec is for installing dry will result in over torqueing the fastener, with possibly catastrophic effect depending on where it's located. |
Thanks for the link! Yes very few manuals if any state dry or lubed for torque values. It has been my personal experiance the the results are more consistent with some sort of lube but like your brake caliper example it is night and day different when it comes to "next time" repairs. This is especially true with lug nuts/wheel bolts. I will seldom let any tire shop put the tires on my cars and when I do I loosen them off at home, lightly lube them and retighten. Tire shops tell me it is illegal to lube wheel nuts. Well they are full of BS because a highway transport cop I know well had that same argument with tire shops and never found that law in our jurisdiction, it doesn't exist!
The exception being my 1 ton Dodge because I am old and those are big wheels and lug nuts. Well guess what! I paid for my negligence. Three weeks ago I had 4 studs fail on the right front wheel and the wheel come loose on the highway! The remaining 4 were so badly damaged from being run off and on dry that it took a lot of torque just to turn them off the studs! Fortunately I caught it before the wheel came right off.
The end result was it cost me $400 for a new front hub, lug nuts and studs. Lesson learned, do the same loosen, lube and re-torque with the truck that I always do with the cars even if it hurts these old arthritic hands!
Oh and by the way in my many years of lubing threads I have never had one fail from this practice. I have had a number of them bind up and stop turning dry though...
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baldessariclan
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Joined: October 14, 2016
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Location: Wichita, KS
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| Posted: Mon May 30, 2022 6:28 am Post subject: Re: Tightening torques |
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Also good to keep in mind that most design torque values operate under the assumption that in addition to the fastener threads being clean and dry, they are also basically within their original dimensional and surface smoothness specs. (i.e. read more-or-less "new").
When you are working with older, "rusty / crusty" bolts, which may (or may not) have had some of the threads stretched a bit, surfaces pitted and rough, etc., you're often well outside of the original "design envelope" used to specify those torque values. And hence the issues with some bolts not tightening up properly when torqued to spec. (e.g. from too much thread friction), while others may stretch or even snap off at spec. torque (lubed / too little thread friction).
Specification torque values only work if the fastener threads themselves are within specifications.
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oprn
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| Posted: Mon May 30, 2022 6:49 am Post subject: Re: Tightening torques |
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Agreed! We are working with 50+ year old parts here, they are not pristine and new!
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TDCTDI
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Joined: August 31, 2013
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| Posted: Mon May 30, 2022 8:23 am Post subject: Re: Tightening torques |
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This failure was far more likely caused by the impact gun wielding assholes hammering on your lugs than any lack of lubricant.
Even with a “torque stick”, the first impact of many air guns is well beyond the specified torque of most vehicles, let alone when the impact jockey leans into one & counts to 15 before moving to the next. Then, when the next fucktard tried to remove them, they’re hammering the lugnut off the stretched, galled threads, over the dirty, corroded threads, only to try to hammer them down again.
Removing, lubing, & retorquing lugnuts after one of those shitbirds have damaged your lug nuts & studs isn’t going to do much for you. Make sure that they install the lug nuts, BY HAND, and torque them, to spec, with a torque wrench. Bring your own torque wrench, you would not believe how many tire shops don’t have one.
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Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.
GOFUNDYOURSELF, quit asking everyone to do it for you!
An air cooled VW will make you a hoarder.
Do something, anything, to your project every day, and you will eventually complete it. |
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oprn
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Joined: November 13, 2016
Posts: 12708
Location: Western Canada
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| Posted: Mon May 30, 2022 7:14 pm Post subject: Re: Tightening torques |
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For sure. It's all about getting the most tires out of the shop in a day. Hammer them puppies on over top rust, dirt and 1/2 pealed threads. Get it out of here and the next one in!
I'm just going to have to buck up and do the heavy ones myself too!
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