Bolt stretch

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Inspector
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Re: Bolt stretch

Post by Inspector » Fri Aug 10, 2018 11:13 am

One thing about a click torque wrench is you can over torque with them. I've corrected mechanics torquing my wheels when they are pushing hard and fast. When the wrench is still moving fast as it clicks it can continue to turn the nut when the head hits the stop, then it will continue to tighten more. The amount over will depend on how much more the wrench is turned. A 250 lb. guy dropping his weight on the wrench will do it every time.

To the OP. If you can't see any signs of damage to the studs or threads you are likely okay. If still not comfortable with the nuts and studs replace them all. Who does the work and bears the cost is another issue. You could take it to a Non Destructive Testing company (NDT) and have them Dye Penetrate or Magnetic particle test them on the car but that won't be cheap. If they do fail then you have evidence you could use to have it fixed at their cost.

Pete

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ctwo
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Re: Bolt stretch

Post by ctwo » Fri Aug 10, 2018 11:16 am

Just an aside on how shops can be... when I was young I bought a set of tires and declined the balancing. I figured I'd do it some time if it needed it. My car has the little hubcabs that just covered the lugnut area. The tech was nice enough to include the old weights in the covers. I was kind of tempted to leave them in there, bouncing around...
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John Hasler
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Re: Bolt stretch

Post by John Hasler » Fri Aug 10, 2018 11:17 am

Now you need to read about how poorly torque correlates with bolt tension.

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BadDog
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Re: Bolt stretch

Post by BadDog » Fri Aug 10, 2018 12:52 pm

Mr Ron wrote:
Fri Aug 10, 2018 10:36 am
BadDog wrote:
Thu Aug 09, 2018 3:05 pm
When it gets that bad, I always wonder if they are going to screw with me, so I retorque when I get home, but at least I don't need an impact to remove nuts from galled studs...
If the nuts were over torqued at the shop, the elastic limit has already been compromised; what good then would it do to retorque?

Why would anyone use a torque wrench to loosen a bolt/nut?
I agree, I wouldn't use a torque wrench to remove a nut, unless I was testing removal torque. And I would expect most of them to work counter-clockwise simply because you do occasionally run into left hand threads in need of a torque wrench.

I understand that torque beyond yield is game over (for anything other than new spec'd bolts intended for that purpose). I would like to think they wouldn't screw with me to that level, but you never know. But it's like going to a restaurant and getting aggravated with your server or sending back incorrect or badly prepared food. You have to wonder. Still, what's the alternative? Say nothing and let them reef on it with a 1/2 torque gun set on kill? Or never let anyone touch one of my vehicles in any way? I'm already nearly there, but can't practically change my own tires, ballance, or alignments. Verifying at home generally puts my mind mostly at ease when I have a significant confrontation at the tire shop, but if they are smart and determined, or just not go far enough for me to readily detect, well I guess they'll get one over on me.

But in any case, by retorquing when I get home, I may not necessarily detect over stretched to yield studs, but I can certainly detect substantially over tightened by being crazy hard to remove, or silly loose, or galled threads, or cross threaded, etc; much better to be found before I get out on the open road.
Russ
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ctwo
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Re: Bolt stretch

Post by ctwo » Fri Aug 10, 2018 2:23 pm

I just put the spoons away last weekend. Of course, I don't do my car tires anymore, but for my motorcycle, nobody will have their hand on that if I can help it.
Standards are so important that everyone must have their own...
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BadDog
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Re: Bolt stretch

Post by BadDog » Fri Aug 10, 2018 5:56 pm

Ever tried changing 33" 8-10+ ply truck tires with spoons? Or off road tires from 35-42"? Yeah, I have a set spoons, I've even got a bead-lever thing from "Tyre Tools" for emergencies, but if I never use them again I'll be happy. :D I know what you mean on the bike too. I don't let anyone touch it, except to mount the tires and balance them. But after convincing myself I can trust them AND watch, I take the wheel to them and it never leaves my sight. Too much riding (literally) on those tires and failure modes are best avoided at all costs...
Russ
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ctwo
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Re: Bolt stretch

Post by ctwo » Sat Aug 11, 2018 5:57 pm

I wouldn't try that, anymore. I once busted a rib on a spoon before. The shop takes more than twice as long and I still have to remove the wheels, etc. Last time I did it and went on a ride and back before lunch. I'd be having lunch in town waiting for them otherwise.
Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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liveaboard
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Re: Bolt stretch

Post by liveaboard » Sun Aug 12, 2018 4:42 am

When I got a motorbike with alloy wheels, I stopped fitting my own tires even though I'm an ego maniac who believes I'm better than the professionals at many things [does this sound familiar?].
I was a car mechanic for a short time in the early 80's. I mounted and balanced tires on customers cars sometimes, but fitting tires is not something I practice much. Those guys do tires all day, every day. And if they kill my wheel, they buy me a new one.

I don't ride anymore. So glad I survived my 30 years of road madness. Had some road rash but amazingly broke no bones.

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BadDog
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Re: Bolt stretch

Post by BadDog » Sun Aug 12, 2018 2:42 pm

Those that have, and those that will... ATGAT.

Between that and wanting high-speed precision balance, I agree. Spoons and static balancing are a last resort.
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Mr Ron
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Re: Bolt stretch

Post by Mr Ron » Thu Aug 16, 2018 11:03 am

Fortunately there is redundancy by the number of studs on a wheel. It would be rare to have all 4,5 or 6 studs to fail at the same time. Loose lug nuts might be more of a problem than tight nuts.
Mr.Ron from South Mississippi

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liveaboard
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Re: Bolt stretch

Post by liveaboard » Thu Aug 16, 2018 11:30 am

One would thing so and yet in reality when they go, they all go.

I just obtained a repair manual for a 1965 Mercedes engine I'm going to be rebuilding soon.
The method given for tightening the rod cap nuts is to mount a dial micrometer on the bolt and then tighten until stretched 0.1mm
The book states you can use a torque wrench if it's known to be an accurate one, but direct measurement is preferred.
hmmm.

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warmstrong1955
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Re: Bolt stretch

Post by warmstrong1955 » Thu Aug 16, 2018 11:56 am

liveaboard wrote:
Thu Aug 16, 2018 11:30 am

I just obtained a repair manual for a 1965 Mercedes engine I'm going to be rebuilding soon.
The method given for tightening the rod cap nuts is to mount a dial micrometer on the bolt and then tighten until stretched 0.1mm
The book states you can use a torque wrench if it's known to be an accurate one, but direct measurement is preferred.
hmmm.
On Deutz engines, the cylinder head capscrews were all torqued by degrees, and in sequence, three times at 60 degrees for the 413 engines I remember.
There were specs for the overall length of the capscrews as well, something you always checked when you removed a head.
There was a torque for a preload, 60Nm, but past that, all by degrees, and no published torque spec other than degrees.

Bill
Today's solutions are tomorrow's problems.

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