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Rear Drop Link - Sheared bolt go case hardened or not
Something didn't feel right.
Inspection of rear suspension found this:
Sheared top bolt, we used what was supplied with new Tarret drop links.
It is supposed to look like this:
Tarret sent new bolt and taped spacer right away.
The rest of the bolt is still inside the welded not on the Bilsten B8, waiting on right angle drill to removed with ez-out, I hope!!
My question is should all of these bolts be hardened or not?
Why did these happen?
This car is daily driver, Autocross, DE and once a year drag strip.
Still it should've held up.
Same thing happened to me recently only with OEM drop links. Taretts now on & surprised to see this. How much use did you get out of them before the failure?
That spacer setup really cantilevers the bolt doesn't it? Does Tarret provide a torque spec for this bolt? And did you follow it? Seems like if that bolt loosened a bit it would break soon after.
Same thing happened to me recently only with OEM drop links. Taretts now on & surprised to see this. How much use did you get out of them before the failure?
8000 miles on street
3 Autocross events
5 Track days
2 Drag times
Just for interest sake are there any markings on the head of the bolt?
Wow, I am glad you asked about the bolts.
I got them out to take pics, and looked at the length, and it appears that my bolt also loosened and then snapped.
I read on another unrelated thread, that this bolt loosened and fell out.
So what does this mean, should a certain type of loctite be used?
Really uncertain on repairing method.
Grade 10.9 is a heat treated, high strength bolt. Judging by the beach marks on the fracture surface, it looks like cyclic fatigue. I'm guessing the joint wasn't torqued properly or lost preload for some reason.
Grade 10.9 is a heat treated, high strength bolt. Judging by the beach marks on the fracture surface, it looks like cyclic fatigue. I'm guessing the joint wasn't torqued properly or lost preload for some reason.
I had a local shop with a fella who is very experienced in suspension do the original install.
I will find out if in fact he used the proper torque for install.
I am not clear of what your seeing in the sheared surface, as the lenght of the bolt clearly shows it had backed out almost 2/3 of the threads that are supposed to be in the strut.
That is judging now, but will be more conclusive when the broken portion is removed from strut.
Are you thinking the torque damage was done at install, and then when bolt backed out, it snapped at the stressed point?
In simple terms, it looks like the bolt backed out, subjecting the bolt to high bending loads, and over time caused a fatigue failure, similar to what happens to a paper clip when you repeatedly bend it back and forth.
Why did the bolt back out? Possibly because it wasn't adequately torqued, or more accurately, the joint wasn't adequately preloaded. Realize that the goal when torquing a bolt is actually to stretch it. It's the amount of stretch than creates the clamp load that keeps the joint tight. That's why critical joints specify a "torque + angle". The torque ensures the mating parts are in contact with each other and the angle is what creates the stretch, via the geometry of the helical threads.
Another possibility is that some other component in the joint yielded (crushed) causing the loss in clamp load, with the same result.
Hope this helps.
Last edited by Coopduc; 08-24-2017 at 10:26 PM.
Reason: Clarification
In simple terms, it looks like the bolt backed out, subjecting the bolt to high bending loads, and over time caused a fatigue failure, similar to what happens to a paper clip when you repeatedly bend it back and forth.
Why did the bolt back out? Possibly because it wasn't adequately torqued, or more accurately, the joint wasn't adequately preloaded. Realize that the goal when torquing a bolt is actually to stretch it. It's the amount of stretch than creates the clamp load that keeps the joint tight. That's why critical joints specify a "torque + angle". The torque ensures the mating parts are in contact with each other and the angle is what creates the stretch, via the geometry of the helical threads.
Another possibility is that some other component in the joint yielded (crushed) causing the loss in clamp load, with the same result.
Hope this helps.
Everything you said makes sense, except the geometry part.
This bolt takes all of the torque from the sway bar doing it's job, isn't it, or am I not understanding where the force from a sway bar goes?
The force from the sway bar is transferred through the bolt into the strut. The clamp load of the bolted connection is what prevents the bolt from bending. When that clamp load is lost then the bolt sees bending, like the paper clip example, leading to the failure.
That’s a high strength bolt. It’s not common for them to break. Install at OEM torque. Make sure the large diameter of the spacer is against the bracket on the shock. Also make sure the bolt is tightened all the way, and not hitting the shock. It shouldn’t break again. Blue Loctite if you’re worried about it coming loose. Make sure the swaybar is not contacting the toe link, it looks close in your pictures.
08-24-2017, 05:59 PM
Rear Drop Link - Sheared bolt go case hardened or not
