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ghiachimp Samba Member
Joined: July 03, 2006 Posts: 65 Location: Kent, UK
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Posted: Mon May 13, 2024 3:33 am Post subject: Torsion bar framehead bolt strength |
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So yesterday I fitted some caster shims and replaced the bottom two framehead bolts with longer ones.
I noticed the old bolts were 8.8 grade but my replacements are 10.9.
I understand the 10.9s are stronger but after doing some research last night (youtube etc.) someone had suggested 10.9s could be more "brittle" and prone to fracturing due to the hardened metal being less malleable that the 8.8s.
So question is: do I need to worry? Should I replace the new 10.9 bolts with 8.8 grade ones?
Thanks! |
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baldessariclan Samba Member
Joined: October 14, 2016 Posts: 1671 Location: Wichita, KS
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Posted: Mon May 13, 2024 5:30 am Post subject: Re: Torsion bar framehead bolt strength |
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I personally wouldn't worry about it. While there is indeed a slight loss of "toughness" with those higher strength bolts, for that particular application doubt it will see high enough loading where brittle fracture is a realistic failure concern. Just make sure to torque them to the correct specifications, and protect from (or at least keep an eye on) rust/corrosion development. _________________ 1971 Standard Beetle — fairly stock / driver
baldessariclan -- often in error, never in doubt... |
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ghiachimp Samba Member
Joined: July 03, 2006 Posts: 65 Location: Kent, UK
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Posted: Mon May 13, 2024 9:56 am Post subject: Re: Torsion bar framehead bolt strength |
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Thanks for putting my mind at rest.
That said I didn't use my torque wrench to tighten them... just put a lot of welly into it
...and if 36 lb/ft is correct (doesn't seem much), I've probably over tightened them.
Will need to check & most likely loosen them a little I think! |
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Busstom Samba Member
Joined: November 23, 2014 Posts: 4451 Location: San Jose, CA
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Posted: Mon May 13, 2024 10:48 pm Post subject: Re: Torsion bar framehead bolt strength |
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ghiachimp wrote: |
...someone had suggested 10.9s could be more "brittle" and prone to fracturing... |
MASSIVE fallacy. _________________ My name's Steve and it's pronounced "Bust 'em" (cuz people think I'm Tom)
cory464 wrote: |
if you aren't perfectly centered in the hole you will have issues when you tap it. |
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DesertSasquatchXploration Samba Member
Joined: April 16, 2021 Posts: 732
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Posted: Tue May 14, 2024 9:51 am Post subject: Re: Torsion bar framehead bolt strength |
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We use 10.9 a lot on custom automated machines they can take a shock load and hold tight, 8.8 stretch and come lose, 12.9 snap like match sticks.
I have 10.9 bolts on my front beam its still attached. |
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ghiachimp Samba Member
Joined: July 03, 2006 Posts: 65 Location: Kent, UK
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Posted: Thu May 16, 2024 3:59 pm Post subject: Re: Torsion bar framehead bolt strength |
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Thanks for your replies and setting my mind at ease. I’ll stick with the 10.9s |
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